Hydrology, Vegetation, and Soils of Riverine 

and Tidal Floodplain Forests of the Lower 

Suwannee River, Florida, and Potential Impacts 

of Flow Reductions

U.S. Geological Survey

Professional Paper 1656 A

Prepared in cooperation with the

Suwannee River Water 

Management District
U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1656A

2002

By Helen M. Light, Melanie R. Darst, Lori J. Lewis, 

U.S. Geological Survey; and David A. Howell, 

Natural Resources Conservation Service, 

U.S. Department of Agriculture

Hydrology, Vegetation, and Soils of Riverine 

and Tidal Floodplain Forests of the Lower 

Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

Prepared in cooperation with the

SUWANNEE RIVER WATER MANAGEMENT DISTRICT
For additional copies please contact:

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. Government.

Library of Congress Cataloging in Publication Data

Light, Helen M.

Hydrology, vegetation, and soils of riverine and tidal floodplain forests of the lower 

Suwannee River, Florida, and potential impacts of flow reductions / by Helen M. Light, 

Melanie R. Darst, Lori J. Lewis, and David A. Howell ; prepared in cooperation with the Suwannee River 

Water Management District.

p. cm. -- (U.S. Geological Survey professional paper ; 1656A)

Includes bibliographical references (p. ).

ISBN 0-607-99590-4

1. Hydrology, Forest--Suwannee River Watershed (Ga. and Fla.) 2.

Streamflow--Suwannee River Watershed (Ga. and Fla.) 3. Hydrology, Forest--Florida. 

4. Streamflow--Florida. 5. Suwannee River Watershed (Ga. and Fla.) I. Darst, Melanie R.

II. Lewis, Lori J. III. Howell, David A. IV. Suwannee River Water Management District (Fla.) V. Title. VI. Series.

GB705.F5 L54 2002

577.68'3'097598--dc21

2002034681

For more information about the USGS and its products:

Telephone: 1-800-USA-MAPS

World Wide Web: http://fl.water.usgs.gov

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director
PREFACE

Preface I

Many areas of the United States have experienced water shortages as a consequence of increased 

water use due to population pressures, industrial 

growth, and changes in agricultural irrigation practices. As a result of these increasing demands on water 

resources, many states have established, or are considering, instream-flow protection programs to ensure 

that the water requirements for ecosystem maintenance will be met. The State of Florida in 1972 

adopted legislation directing the water management 

districts to establish minimum flows and levels 

(MFLs) for all watercourses, and minimum levels for 

aquifers and surface waters, in their respective regions. 

Section 373.042 of the Florida Statutes specifies that a 

minimum flow for a watercourse is the flow at which 

further withdrawals would be significantly harmful to 

the water resources or ecology of the area. Similarly, 

the Statute defines the minimum level as the level of 

water in an aquifer, or level of surface water, at which 

further withdrawals would be significantly harmful to 

the water resources of the area. The Statute also allows 

the development of minimum flows and levels using 

the "best information available" and the recognition of 

seasonal variation in setting the flows and levels. 

The Suwannee River Water Management District 

(SRWMD) in the north-central part of the State is one 

of five regional water management districts in Florida. 

The District’s first priority is to set MFLs for the lower 

Suwannee River, from its confluence with the Santa Fe 

River to the Gulf of Mexico. The SRWMD began the 

process for setting MFLs in 1994 with a series of longterm cooperative studies with the U.S. Geological Survey that included data collection, analysis, and interpretation. The USGS program culminated in the 

completion of three major studies conducted to understand the effects that reduced flow in the river could 

have on the forested floodplain and the mixing of 

freshwater and saltwater in the estuary, as well as the 

effects that ground-water withdrawals could have on 

flows in the river. These studies are reported in Chapters A, B, and C of this Professional Paper series; additionally, a summary of the program is presented in 

Chapter D, which includes a discussion of how the 

results from these three studies can be used together 

by the water management district. 

Chapter A of the series describes the hydrology, 

vegetation, and soils of the forested floodplain of the 

lower Suwannee River. The chapter goes on to 

describe the relation of forest types and other floodplain characteristics to long-term river flow, and to 

estimate potential impacts on the floodplain if river 

flows were reduced. Chapter B focuses on flow and 

the mixing of freshwater and saltwater in the lower 

river and estuary. Salinity and other hydrologic data 

collected during a period of unusually low flow were 

used to calibrate a three-dimensional hydrodynamic 

and transport model that simulates time-varying water 

levels, currents (lateral, longitudinal, and vertical), and 

salinity conditions. This chapter includes important 

discussions of modeled scenarios and hydrologic 

changes that could result from a reduction of flow in 

the river. Reductions in streamflow could come from 

changes in climatic conditions or from direct withdrawal, but may also come from ground-water pumpage adjacent to or many miles from the river. Chapter 

C presents a discussion of hydrologic conditions governing the interaction between ground water and surface water, an evaluation of the magnitude and timing 

of water exchanges between the lower Suwannee 

River and the Upper Floridan aquifer using historical 

data, and the models that were used to simulate the 

exchanges. Also presented in this chapter is a discussion of how a hydrologic model could be used to evaluate hypothetical water-use scenarios, and the groundwater and surface-water exchanges that could result 

from these hypothetical conditions. Chapter D summarizes the cooperative program and highlights the 

importance of this multidisciplinary program to our 

understanding of the hydrology in the lower Suwannee 

Basin – an understanding borne out of an extensive 

data collection program and complex interpretive 

studies. Chapter D provides a “roadmap” for water 

managers to make better use of the integrated results 

of these studies.
II Preface
Contents III

CONTENTS

Preface ................................................................................................................................................................................... I

Glossary................................................................................................................................................................................. IX

List of Scientific Names Used and Common Name Equivalents .......................................................................................... XII

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

Introduction ........................................................................................................................................................................... 3

Purpose and Scope....................................................................................................................................................... 3

Acknowledgments ....................................................................................................................................................... 4

Setting .......................................................................................................................................................................... 5

Methods of Study................................................................................................................................................................... 8

Data Collection ............................................................................................................................................................ 9

Study Sites ......................................................................................................................................................... 9

Hydrologic Measurements................................................................................................................................. 12

Soil Sampling..................................................................................................................................................... 13

Vegetation Sampling.......................................................................................................................................... 13

Data Analysis............................................................................................................................................................... 13

Long-Term River Flow and Stage ..................................................................................................................... 13

Defining and Mapping Forest Types ................................................................................................................. 18

Flow-Dependent Characteristics of Floodplain ................................................................................................. 20

Impacts of Flow Reductions .............................................................................................................................. 25

Hydrologic Characteristics of the River ................................................................................................................................ 26

Flow ............................................................................................................................................................................. 26

Stage and Tidal Range ................................................................................................................................................. 27

Storm Surge ................................................................................................................................................................. 29

Salinity......................................................................................................................................................................... 29

Topography and Hydrology of Forested Floodplain.............................................................................................................. 29

Land-Surface Elevations, Hydrologic Conditions, and Forest Types at Transects...................................................... 29

Salinity in Floodplain Water Bodies of Lower Tidal Reach........................................................................................ 37

Soil Characteristics................................................................................................................................................................ 39

Taxonomic Classification............................................................................................................................................. 39

Texture and Saturation ................................................................................................................................................. 40

Conductivity in Lower Tidal Reach............................................................................................................................. 42

Forest Composition and Distribution..................................................................................................................................... 44

Important Tree Species ................................................................................................................................................ 45

Forest Type Composition............................................................................................................................................. 48

Oak/Pine Uplands .............................................................................................................................................. 49

Riverine Wetlands.............................................................................................................................................. 49

Upper Tidal Wetlands........................................................................................................................................ 55

Lower Tidal Wetlands ....................................................................................................................................... 57

Characteristics of Forest Type Composition................................................................................................................ 63

Flow-Dependent characteristics Of Floodplain ..................................................................................................................... 66

Inundation and Saturation............................................................................................................................................ 66

Flood Depths................................................................................................................................................................ 70

Salinity......................................................................................................................................................................... 73

Potential Impacts of Flow Reductions................................................................................................................................... 74

Changes in Floodplain Forest Composition................................................................................................................. 74

Change to Drier Forest Types............................................................................................................................ 74

Upstream Movement of Tidal Forests ............................................................................................................... 77
IV Contents

Upstream Movement of Marshes and Salt-Tolerant Forests............................................................................. 78

Summary of Forest Composition Changes........................................................................................................ 82

Loss of Inundated and Saturated Area in Floodplain Forests ..................................................................................... 82

Ecological Consequences of Flow Reductions .......................................................................................................... 86

Summary ............................................................................................................................................................................... 90

References............................................................................................................................................................................. 93

APPENDIXES

I. Median monthly high, median daily high, and median daily low stages at transects and gages in tidal

 reaches of the lower Suwannee River, Florida ....................................................................................................... 101

II. Median land-surface elevations of forest types at transects in the floodplain of the lower Suwannee 

River, Florida........................................................................................................................................................... 101

III. Floodplain hydrology observations and measurements made at study sites in floodplain forests of the 

lower Suwannee River, Florida ............................................................................................................................... 102

IV. Salinity of ponds and tidal creeks in the floodplain of the lower Suwannee River, Florida .................................. 115

V. Soil profile descriptions for floodplain forest types of the lower Suwannee River, Florida ................................... 116

VI. Percentage of inundated and saturated area for each forest type and transect in the riverine reach in 

relation to flow in the lower Suwannee River, Florida............................................................................................ 122

VII. Flow duration curves for five hypothetical flow reductions compared to the existing flow in the lower 

Suwannee River, Florida ......................................................................................................................................... 124

FIGURES

1-2. Maps showing:

1. Drainage basin of the Suwannee River in Florida and Georgia ..................................................................... 4

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

Suwannee River, Florida................................................................................................................................. 6

3. Flow chart showing basic study components and analytical approach for describing hydrology, vegetation, 

and soils of the floodplain and estimating impacts of flow reductions in the lower Suwannee River, Florida ...... 9

4-7. Photographs showing:

4. Measurement of horizontal distances with meter tape extended between numbered wooden stakes in 

UTswl forest on MS transect in the lower Suwannee River floodplain, Florida..................................................... 11

5. Surveying with a tripod-mounted level in LTsw2 forest on TK transect in the lower Suwannee River 

floodplain, Florida................................................................................................................................................... 11

6. Examination of soil auger contents in UTsw2 forest at KN transect in the lower Suwannee River 

floodplain, Florida................................................................................................................................................... 13

7. Measuring and identifying canopy trees in UTsw1 forest on MS transect in the lower Suwannee River 

floodplain, Florida................................................................................................................................................... 14

8-9. Graphs showing:

8. Daily mean stage at gages and riverine transects in relation to flow in the lower Suwannee River,

Florida............................................................................................................................................................. 17

9. Daily high and low stage at gages and tidal transects in relation to flow in the lower Suwannee River, 

Florida............................................................................................................................................................. 17

10-12. Flow charts showing:

10. Methods for defining and mapping forest types in the lower Suwannee River floodplain, Florida............... 19

11. Methods for calculating area of each riverine forest type that is inundated or saturated in relation to 

flow in the lower Suwannee River, Florida .................................................................................................... 23

12. Methods for calculating flood depths for each forest type at each transect in the lower Suwannee River 

floodplain, Florida .......................................................................................................................................... 24

13-16. Graphs showing:

13. Mean and median monthly flows of the lower Suwannee River, Florida, 1933-99 ....................................... 26

14. River stage during the 1997, 1998, and 1999 water years at four gaging stations on the lower Suwannee 

River, Florida .................................................................................................................................................. 28
Contents V

15. Land-surface elevations and forest types at floodplain transects in relation to long-term hydrologic 

conditions in the lower Suwannee River, Florida........................................................................................... 30

16. Forest type elevations in relation to daily high river stage from 1985 to 1999 at transect locations in 

the upper and lower tidal reaches of the Suwannee River, Florida................................................................. 34

17-19. Photographs showing:

17. Tidal creek at low tide in LTsw2 forest on TK transect in the lower Suwannee River floodplain, Florida ... 36

18. Shore of the Suwannee River, Florida, near DM transect at very low tide .................................................... 36

19. A well-defined hummock that is large enough to support several trees on BC transect in the lower 

Suwannee River floodplain, Florida ............................................................................................................... 37

20. Graph showing salinity of surface-water samples collected at selected sites in lower tidal forests in the 

floodplain of the lower Suwannee River, Florida.................................................................................................... 38

21. Photograph showing isolated pond at BC transect in the winter in the lower Suwannee River 

floodplain, Florida................................................................................................................................................... 38

22-26. Graphs showing:

22. Texture of soils in floodplain forests of the lower Suwannee River, Florida ................................................. 41

23. Soil conductivity ranges in lower tidal forests of the Suwannee River floodplain, Florida ........................... 44

24. Area of uplands and wetlands that are presently or were historically forested in the 10-year floodplain 

of the lower Suwannee River, Florida ............................................................................................................ 45

25. Distribution of selected canopy tree species in relation to distance from the mouth of the Suwannee 

River, Florida .................................................................................................................................................. 47

26. Area of wetland forest types in the floodplain of the lower Suwannee River, Florida................................... 49

27-38. Photographs showing:

27. Buttressed trunk of a Taxodium distichum tree growing on the banks of Rock Bluff Spring run in 

the riverine reach of the lower Suwannee River, Florida................................................................................ 52

28. Clumps of Forestiera acuminata trees in the riverine reach of the lower Suwannee River 

floodplain, Florida .......................................................................................................................................... 53

29. Carya aquatica with a flared base growing in Rblh1 forest at the LL transect in the lower Suwannee 

River floodplain, Florida ................................................................................................................................ 53

30. Rblh2 forest in winter on the MS transect in the lower Suwannee River floodplain, Florida........................ 54

31. Large Quercus virginiana in high bottomland hardwood forest in the riverine reach of the lower 

Suwannee River floodplain, Florida ............................................................................................................... 54

32. Swollen bases of Nyssa aquatica and Taxodium distichum in UTsw1 forest at the MS transect in 

the lower Suwannee River floodplain, Florida ............................................................................................... 55

33. UTmix forest on the KI transect in the lower Suwannee River floodplain, Florida....................................... 57

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

lower Suwannee River floodplain, Florida ..................................................................................................... 59

35. LTmix forest at SN transect, which receives regular tidal inundation from a small tributary of 

Sandfly Creek in the lower Suwannee River floodplain, Florida ................................................................... 60

36. Root mat on the bank of East Pass in the lower Suwannee River, Florida..................................................... 60

37. Sabal palmetto and Pinus taeda dominate the canopy of hammocks in the lower tidal reach of the 

Suwannee River floodplain, Florida ............................................................................................................... 61

38. Sabal palmetto trees growing on slightly higher ground in a marsh on East Pass in the lower 

Suwannee River, Florida................................................................................................................................. 62

39-42. Graphs showing:

39. Species richness of canopy and subcanopy trees in floodplain forests of the lower Suwannee 

River, Florida .................................................................................................................................................. 63

40. Basal area of canopy trees in floodplain forests of the lower Suwannee River, Florida ................................ 63

41. Average size of canopy trees in floodplain forests of the lower Suwannee River, Florida ............................ 64

42. Density of canopy trees in floodplain forests of the lower Suwannee River, Florida .................................... 64

43. Photograph showing dense stand of trees in LTsw1 forest on DM transect in the lower Suwannee 

River floodplain, Florida ......................................................................................................................................... 64

44-49. Graphs showing:

44. Density of subcanopy trees in floodplain forests of the lower Suwannee River, Florida............................... 65

45. Density of multiple-trunked canopy trees in floodplain forests of the lower Suwannee River, Florida ........ 65

46. Density of canopy-size snags in floodplain forests of the lower Suwannee River, Florida ........................... 66
VI Contents

47. Estimated amount of inundated area in riverine wetland forests in relation to flow in the lower 

Suwannee River, Florida................................................................................................................................. 67

48. Estimated amount of saturated area in riverine wetland forests in relation to flow in the lower 

Suwannee River, Florida................................................................................................................................. 68

49. Duration of inundation and saturation of riverine forest types in the floodplain of the lower 

Suwannee River, Florida................................................................................................................................. 69

50. Photograph showing floodwaters more than 3 meters deep during the 25-year flood in 1998 in a 

bottomland hardwood forest near the FK transect in the lower Suwannee River floodplain, Florida .................... 70

51-55. Graphs showing:

51. Flood depths in riverine and upper tidal forest types in the floodplain of the lower Suwannee 

River, Florida .................................................................................................................................................. 71

52. Flood depths in wetland forests in the floodplain of the lower Suwannee River, Florida, in relation 

to distance from river mouth........................................................................................................................... 72

53. Estimated decreases in duration of inundation for Rsw1/sw2 forests if flows were reduced in the 

lower Suwannee River, Florida....................................................................................................................... 75

54. Area of forest types estimated to change to next drier type if flows were reduced in the lower 

Suwannee River, Florida................................................................................................................................. 77

55. Estimated upstream movement of flood depth at the reach boundary between UTmix and Rblh1 

forests if flows were reduced in the lower Suwannee River, Florida ............................................................. 78

56. Map showing estimated upstream movement of reach boundary between Rblh1 and UTmix forests if 

flows were reduced in the lower Suwannee River, Florida ..................................................................................... 79

57. Graph showing area of tidal forests estimated to move upstream if flows were reduced in the lower 

Suwannee River, Florida ......................................................................................................................................... 80

58. Map showing area of lower tidal forests estimated to convert to marsh if flows were reduced 28 cubic 

meters per second (1,000 cubic feet per second) in the lower Suwannee River, Florida........................................ 81

59-61. Graphs showing:

59. Area of lower tidal forests estimated to convert to marsh if flows were reduced in the lower 

Suwannee River, Florida................................................................................................................................. 82

60. Percent loss of inundated area in floodplain forests of the riverine reach of the lower 

Suwannee River, Florida, estimated for five hypothetical flow reductions in relation to flow at 

which reduction occurs................................................................................................................................... 84

61. Percent loss of saturated area in floodplain forests of the riverine reach of the lower 

Suwannee River, Florida, estimated for five hypothetical flow reductions in relation to flow at 

which reduction occurs................................................................................................................................... 85

TABLES

1. Names of forest types in the 10-year floodplain of the lower Suwannee River, Florida........................................ 8

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

floodplain, Florida .................................................................................................................................................. 10

3. Surface-water gaging stations used in hydrologic analyses of the lower Suwannee River, Florida....................... 12

4. Methods and source data used to develop stage-discharge ratings at transects in the lower Suwannee 

River floodplain, Florida......................................................................................................................................... 16

5. Methods and source data used to calculate long-term river stage statistics at transects in the lower 

Suwannee River floodplain, Florida ....................................................................................................................... 18

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

River, Florida ......................................................................................................................................................... 21

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

Suwannee River, Florida......................................................................................................................................... 22

8. Basic flow characteristics of the lower Suwannee River, Florida, 1933-99 ........................................................... 27

9. Taxonomic classification of soils in floodplain forests of the lower Suwannee River, Florida.............................. 39

10. Continuously saturated soils in wetland forest types of the lower Suwannee River floodplain, 

Florida, 1996-99 ..................................................................................................................................................... 42

11. Soil conductivity in lower tidal forests of the Suwannee River floodplain, Florida............................................... 43
Contents VII

12. Important canopy and subcanopy species in riverine and tidal wetland forests in the floodplain of 

the lower Suwannee River, Florida......................................................................................................................... 46

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

10-year floodplain of the lower Suwannee River, Florida...................................................................................... 48

14. Canopy composition in riverine wetlands and oak/pine upland forests in the floodplain of the lower 

Suwannee River, Florida......................................................................................................................................... 50

15. Subcanopy composition in riverine wetlands and oak/pine upland forests in the floodplain of the 

lower Suwannee River, Florida............................................................................................................................... 51

16. Canopy composition in upper tidal wetland forests in the floodplain of the lower Suwannee 

River, Florida .......................................................................................................................................................... 56

17. Subcanopy composition in upper tidal wetland forests in the floodplain of the lower Suwannee 

River, Florida .......................................................................................................................................................... 56

18. Canopy composition in lower tidal wetland forests in the floodplain of the lower Suwannee 

River, Florida .......................................................................................................................................................... 58

19. Subcanopy composition in lower tidal wetland forests in the floodplain of the lower Suwannee 

River, Florida .......................................................................................................................................................... 58

20. Comparison of four different measures of long-term hydrologic conditions used to calculate 

hydrologic changes in riverine swamps resulting from hypothetical flow reductions in the lower 

Suwannee River, Florida......................................................................................................................................... 76

21. Percent of forest types estimated to change to next drier type if flows were reduced in the lower 

Suwannee River, Florida......................................................................................................................................... 76

22. Distance that tidal forests are estimated to move upstream if flows were reduced in the lower 

Suwannee River, Florida......................................................................................................................................... 79

23. Distance that lower tree line is estimated to move upstream if flows were reduced in the lower 

Suwannee River, Florida......................................................................................................................................... 80

24. Summary of wetland forest composition changes expected to occur if flows were reduced in the 

lower Suwannee River, Florida............................................................................................................................... 83

25. Estimated loss of inundated area in riverine forests for five hypothetical flow reductions, in relation 

to selected flows in the lower Suwannee River, Florida......................................................................................... 84

26. Estimated loss of saturated area in riverine forests for five hypothetical flow reductions, in relation to 

selected flows in the lower Suwannee River, Florida ............................................................................................. 86

27. Potential ecological consequences of flow reductions on the forested floodplain of the lower 

Suwannee River, Florida......................................................................................................................................... 87
VIII Contents

CONVERSION FACTORS, DATUMS, AND UNIT ABBREVIATIONS

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD of 1929)—a geodetic 

datum derived from a general adjustment of the first-order level nets of the United States and Canada, formerly called Sea 

Level Datum of 1929.

Horizontal datum: In this report, horizontal coordinate information is referenced to the North American Datum of 1927 

(NAD27).

AGENCY ABBREVIATIONS

 Multiply By To obtain

centimeter (cm) 0.3937 inch

meter (m) 3.28 foot

kilometer (km) 0.62 mile

river kilometers1 (rkm)

1 See glossary for definition

0.62 river miles

square centimeter (cm2) 0.155 square inch

square meter (m2) 10.76 square foot

square kilometer (km2) 0.3861 square mile

hectare (ha) 2.471 acre

hectare (ha) 0.003861 square mile

square meter per hectare (m2/ha) 4.355 square foot per acre

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

FFWCC = Florida Fish and Wildlife Conservation Commission

LSNWR = Lower Suwannee National Wildlife Refuge

NRCS = Natural Resources Conservation Service

SRWMD = Suwannee River Water Management District

USDA = U.S. Department of Agriculture

USGS = U.S. Geological Survey
Glossary IX

GLOSSARY

2-year, 1-day maximum flow (or stage) is the annual 1-day 

high flow that typically occurs once every 2 years and 

has a 50 percent chance of occurring in any given year. 

(Also known as the 2-year, 1-day high).

2-year, 14-day maximum threshold flow (or stage) is the 

annual 14-day threshold high flow that typically occurs 

once every 2 years and has a 50 percent chance of 

occurring in any given year. The maximum threshold 

14-day flow is the highest flow that is equaled or 

exceeded for 14 consecutive days during a year; 

whereas the more commonly used maximum 14-day 

flow is the highest mean flow for 14 consecutive days. 

These two types of statistics are described and compared graphically in figure 17 of Leitman and others 

(1984). (Also known as the 2-year, 14-day threshold 

flood).

Argillic horizon is normally a subsurface soil horizon that 

shows evidence of clay illuviation and has a substantially higher percentage of clay than the overlying soil 

material. 

Basal area is the cross-sectional area of a tree trunk (in m2

), 

which is calculated from dbh (in cm) using the formula 

πr

2, in which π= 3.1416 and r = dbh/2. (See relative 

basal area.)

Belt transect is a long, narrow rectangular sampling area 

oriented along a centerline with a width of a few meters 

on one or both sides of the line. 

Bottomland hardwoods (Rblh1, Rblh2, Rblh3, and 

UTblh) are forests on levees, flats, and slopes of floodplains that are flooded continuously for several weeks 

or longer every 1 to 3 years and contain tree species 

adapted to periodic inundation and saturation.

Density is the number of individual plants in a forest type 

or sampling area. Trees with multiple trunks were 

counted as one individual. (See relative density.)

Diameter at breast height (dbh) is the diameter of a tree 

trunk measured at about 1.4 to 1.5 m above the ground. 

The dbh of trees with swollen bases were measured for 

diameter above the swelling.

Digital orthophoto quadrangle (DOQ) is a digital image 

of color-infrared photographs (scale 1:40,000) that has 

been rectified to an orthographic projection. The geographic extent of a DOQ is equivalent to one-quarter of 

a USGS quadrangle map. 

Dominant species are the most important species within a 

forest type, determined by the following methods. 

Species are first ranked by rba for canopy and rd for 

subcanopy. If the rba or rd for the top species exceeds 

50 percent, it is the only dominant species. If the rba or 

rd for the top species is less than 50 percent, then percentages for additional dominant species are added one 

at a time in ranked order until the sum exceeds 50 percent. All other species are not considered to be dominant. (See importance of a species.)

Floodplain refers to the 10-year floodplain of the lower 

Suwannee River and covers approximately 18,600 ha 

of forests, not including open water in the main river 

channel. 

Flow ranges used in this report include low flows, less than 

120 m3/s (4,300 ft3/s); medium flows, from 120 to 

297 m3

/s (4,300-10,590 ft3/s), and high flows, greater 

than 297 m3

/s (10,590 ft3/s). All flow values refer to 

Branford-Fort White flow (the combined flow of the 

Suwannee River at Branford and Santa Fe River near 

Fort White), unless otherwise indicated.

Forest types are groups of canopy tree species that usually 

grow together in a relatively distinct and recognizable 

community. In this report, forest types have been 

botanically defined based on both vegetation sampling 

and aerial photographic signatures. (see general forest 

types and specific forest types)

General forest types refer to the following 10 forest types, 

some of which are combinations of specific types: 

oak/pine, Rblh2/blh3, Rblh1, Rsw1/sw2, UTblh, 

UTmix, UTsw1/sw2, LTham, LTmix, and LTsw1/sw2. 

Hydrologic characteristics of general forest types were 

used in calculating impacts from flow reductions 

because changes of general forest types were considered to be more important than changes in specific 

types. (See forest types and specific forest types.)

Geographic information system (GIS) is a collection of 

computer software and data files designed to store, 

analyze, and display geographically referenced information.

Hammocks (LTham) refer to hydric 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. 

High flows are greater than 297 m3/s (10,590 ft3

/s). (See 

flow ranges.)
X Glossary

Hummocks are mounds around the bases of trees that are 

elevated above the surrounding ground. Hummocks can 

be found in all forests of the floodplain but are most 

prominent in the lower tidal reach. 

Importance of a species is used to compare species in a forest type or sampling area and is based on relative basal 

area for canopy species and relative density for subcanopy species. (See dominant species.)

Kandic horizon is a subsurface soil horizon that has a substantially higher percentage of clay than the overlying 

soil material and has a relatively low cation-exchange 

capacity.

Lower Suwannee River is that portion of the river from its 

confluence with the Santa Fe River to the mouth of the 

river at the Gulf of Mexico. 

Lower tidal reach (LT) is that part of the floodplain forest 

of the lower Suwannee River having a canopy forest 

composition influenced by tides and salinity in the 

water and soil. It extends from rkm 21.6 downstream 

to the tree line. Data for the lower tidal reach is generally presented in this report with a light blue background color. 

Low flows are flows less than 120 m3

/s (4,300 ft3/s). (See 

flow ranges.)

Maximum threshold n-day flow is the highest flow that is 

equaled or exceeded for n consecutive days during a 

year. It differs from the more commonly used maximum n-day flow, which is calculated from the highest 

mean flow for n consecutive days during a year. These 

two types of statistics are described and compared 

graphically in figure 17 of Leitman and others (1984). 

(See 2-year, 14-day maximum threshold flow.)

Median daily high stage (MDH) is the median of all the 

daily high stages in the period of record. 

Median daily low stage (MDL) is the median of all the 

daily low stages in the period of record. 

Median monthly high stage (MMH) is the median of all 

the monthly high stages in the period of record. 

Medium flows are flows from 120 to 297 m3/s (4,300-

10,590 ft3

/s). (See flow ranges.)

Mixed forests (UTmix and LTmix) are tidal forest types 

dominated by a mixture of swamp and bottomland 

hardwood tree species. 

Non-tidal refers to daily stage fluctuations less than 6 cm.

Oak/pine upland forests (oak/pine) are present at high elevations in the 10-year floodplain and are only inundated during the highest floods. Many tree species 

present in upland forests cannot survive more than brief 

periods of inundation. (See uplands.)

Precise Lightweight Global Positioning System Receiver 

(PLGR) is a Global Positioning System (GPS) receiver 

with encoded data that enables it to remove intentional 

errors that have been built into signals transmitted by 

GPS satellites for security purposes.

Relative basal area (rba) is the percentage of a species in a 

forest type or sampling area based on basal area. It is 

calculated by dividing the total basal area of that species (in m2

) by the total basal area of all species (in m2) 

in that forest type or sampling area.

Relative density (rd) is the percentage of a species in a forest type or sampling area based on density. It is calculated by dividing the total density of that species (in 

number of individuals) by the total density of all species (in number of individuals) in that forest type or 

sampling area.

River kilometers (rkm) are used to 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′′. 

Riverine reach (R) is that part of the floodplain forest of 

the lower Suwannee River having a canopy forest composition unaffected by tides. It extends from rkm 106 

at the confluence of the Suwannee and Santa Fe Rivers 

downstream to either rkm 37 for swamps or rkm 45.2 

for bottomland hardwoods. Data for the riverine reach 

is generally presented in this report with a yellow background color.

Sea level refers to the National Geodetic Vertical Datum of 

1929 (NGVD of 1929), which is a geodetic datum 

derived from a general adjustment of the first-order 

level nets of the United States and Canada, formerly 

called Sea Level Datum of 1929.

Snag is a dead tree with a dbh of 10 cm or more and a 

height of 3 m or taller. A tree was not considered to be a 

snag if any leaves were alive.

Specific forest types refer to the following 14 forest types: 

oak/pine, Rblh3, Rblh2, Rblh1, Rsw2, Rsw1, UTblh, 

UTmix, UTsw2. UTsw1, LTham, LTmix, LTsw2, 

LTsw1. (See forest types and general forest types.)

Storm surge is a rising or piling up of water against the 

shore during a storm that may result in flooding of 

coastal areas. It occurs as a result of wind stresses 

acting on the surface of the sea and atmospheric-pressure differences. 

Swamps (Rsw1, Rsw2, UTsw1, UTsw2, LTsw1, and 

LTsw2) are forests in the lowest elevations of the floodplain that are either inundated or saturated most of the 

time. Swamps contain tree species that have special 

adaptations for survival in anoxic soils. 
Glossary XI

Tree line is a general east-west boundary line across the 

lower tidal floodplain, which has mostly forests on the 

upstream side and marshes on the downstream side. 

The tree line is the downstream limit of the study area. 

Uplands generally refer to areas that are not considered 

wetlands or deepwater habitats by the U.S. Fish and 

Wildlife Service classification system (Cowardin and 

others, 1979; Reed, 1988). The percentage of these 

areas that would be classified as non-wetlands according to criteria in State and Federal wetland regulations 

is not known. (See Oak/pine upland forests.)

Upper tidal reach (UT) is that part of the floodplain forest 

of the lower Suwannee River having a canopy forest 

composition partially influenced by tides. It extends 

from either rkm 37 for swamps or rkm 45.2 for bottomland hardwoods downstream to rkm 21.6. Data for 

the upper tidal reach is generally presented in this 

report with a light green background color.

Water year is a 12-month period beginning October 1, and 

ending September 30, which is used for analysis of 

USGS gage data. The beginning and ending dates usually coincide with the normal low-flow period of north 

Florida streams. A water year is named for the year in 

which it ends. For example, the water year beginning 

October 1, 1998, and ending September 30, 1999, is 

called the 1999 water year. 

Wetlands generally refer to areas that are considered wetlands by the U.S. Fish and Wildlife Service classification system (Cowardin and others, 1979; Reed, 1988). 

The percentage of these areas that would be classified 

as jurisdictional wetlands according to criteria in State 

and Federal wetland regulations is not known.
XII List of Scientific Names Used and Common Name Equivalents

LIST OF SCIENTIFIC NAMES USED AND COMMON

NAME EQUIVALENTS

[Plant nomenclature used in this report follows that by Godfrey (1988) unless otherwise 

indicated. Names of varieties have been omitted in the body of the report]

Scientific name Common name

Acer rubrum L. red maple

Aesculus pavia L. red buckeye

Amorpha fruticosa L. false-indigo

Ampelopsis arborea (L.) Koehne pepper-vine

Asimina parviflora (Michx.) Dunal small-fruited pawpaw

Baccharis glomeruliflora Pers. groundsel tree

Berchemia scandens (Hill) K. Koch supple-jack

Betula nigra L. river birch

Bignonia capreolata L. cross-vine

Bumelia lanuginosa (Michx.) Pers. gum bumelia

Bumelia reclinata (Michx.) Vent. var. reclinata smooth bumelia

Campsis radicans (L.) Seem. ex Bureau trumpet vine

Carpinus caroliniana Walt. ironwood

Carya aquatica (Michx. f.) Nutt. water hickory

Carya glabra (Mill.) Sweet pignut hickory

Celtis laevigata Nutt. hackberry

Cephalanthus occidentalis L. buttonbush

Cornus foemina Mill. stiffcornel dogwood

Crataegus flava Ait. yellow haw

Crataegus marshallii Eggl. parsley haw

Crataegus viridis L. green haw

Crinum americanum L.1 swamp-lily

Cyrilla racemiflora L. titi

Decumaria barbara L. climbing hydrangea

Diospyros virginiana L. persimmon

Forestiera acuminata (Michx.) Poir. in Lam. swamp-privet

Fraxinus caroliniana Mill. pop ash

Fraxinus profunda (Bush) Bush pumpkin ash

Gleditsia aquatica Marsh. water locust

Halesia carolina L. little silverbell

Ilex cassine L. dahoon

Ilex decidua Walt.var. curtissii Fern. possum-haw

Ilex opaca Ait.var. opaca American holly

Ilex vomitoria Ait. yaupon

Itea virginica L. Virginia willow

Juniperus silicicola (Small) Bailey 1 southern red cedar

Liquidambar styraciflua L. sweetgum

Lygodium japonicum (Thunb.) Sw. 1 Japanese climbing fern

Lyonia ferruginea (Walt.) Nutt. rusty lyonia

Magnolia grandiflora L. southern magnolia

Magnolia virginiana L. sweetbay

Myrica cerifera L. wax-myrtle

Nyssa aquatica L. water tupelo

Nyssa ogeche Bartr. ex Marsh. Ogeechee tupelo

Nyssa biflora Walt.1 swamp tupelo

Nyssa sylvatica Marsh. sour gum

Osmanthus americanus (L.) A. Gray wild olive

Osmunda cinnamomea L.1 cinnamon fern

Ostrya virginiana (Mill.) K. Koch eastern hophornbeam
List of Scientific Names Used and Common Name Equivalents XIII

Persea borbonia (L.) Spreng. red bay

Persea palustris (Raf.) Sarg. swamp red bay

Pinus elliottii Engelm. var. elliottii slash pine

Pinus glabra Walt. spruce pine

Pinus taeda L. loblolly pine

Planera aquatica J. F. Gmel. planer-tree

Porella pinnata L.2 liverwort

Quercus austrina Small bluff oak

Quercus chapmanii Sarg. Chapman oak

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 michauxii Nutt. swamp-chestnut oak

Quercus myrtifolia Willd. myrtle oak

Quercus nigra L. water oak

Quercus virginiana Mill. live oak

Rhus copallina L. winged sumac

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

Salix caroliniana Michx. Carolina willow

Salix nigra L. black willow

Sapium sebiferum (L.) Roxb. Chinese tallow tree

Sebastiania fruticosa (Bartr.) Fern. Sebastian bush

Smilax laurifolia L. bamboo-vine

Styrax americanum Lam. American snowbell

Symplocos tinctoria (L.) L’Her. horse-sugar

Taxodium ascendens Brongn. pond cypress

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

Tilia caroliniana Mill.1 basswood

Toxicodendron radicans (L.) Kuntze poison ivy

Ulmus alata Michx. winged elm

Ulmus americana L. American elm

Ulmus crassifolia Nutt. cedar elm

Vaccinium arboreum Marsh sparkleberry

Vaccinium corymbosum L. highbush blueberry

Vaccinium elliottii Chapm. mayberry

Vaccinium stamineum L. deerberry

Viburnum obovatum Walt. small viburnum

Vitis cinerea (Engelm. ex Gray) Millardet var.

floridana Munson

downy winter grape

Vitis rotundifolia Michx. muscadine

1

 Clewell (1985)

2 Breil (1970)

Scientific name Common name

Abstract 1

Hydrology, Vegetation, and Soils of Riverine and 

Tidal Floodplain Forests of the Lower Suwannee 

River, Florida, and Potential Impacts of Flow 

Reductions

By Helen M. Light, Melanie R. Darst, Lori J. Lewis, U.S. Geological Survey; and David A. 

Howell, Natural Resources Conservation Service, U.S. Department of Agriculture

Abstract 

A study relating hydrologic conditions, soils, and vegetation of floodplain forests to 

river flow was conducted in the 

lower Suwannee River, Florida, 

from 1996 to 2000. The study 

was done by the U.S. Geological 

Survey in cooperation with the 

Suwannee River Water Management District to help determine 

the minimum flows and levels 

required for wetlands protection. The study area included 

forests within the 10-year floodplain of the Suwannee River 

from its confluence with the 

Santa Fe River to the tree line 

(lower limit of forests) near the 

Gulf of Mexico, and covered 

18,600 hectares (ha) of forests, 

75 percent of which were wetlands and 25 percent uplands. 

The floodplain was divided into 

three reaches, riverine, upper 

tidal, and lower tidal, based on 

changes in hydrology, vegetation, and soils with proximity to 

the coast.

The Suwannee River is 

the second largest river in 

Florida in terms of average 

discharge. Median flow at the 

confluence of the Suwannee and 

Santa Fe Rivers is approximately 181 cubic meters per 

second (m3/s) or 6,480 cubic 

feet per second (ft3

/s) (1933-99). 

At the upper end of the riverine 

reach, river stages are unaffected 

by tides and have a typical 

annual range of 4.1 meters (m). 

Tides affect river stages at low 

and medium flows in the upper 

tidal reach, and at all flows in 

the lower tidal reach. Median 

tidal range at the mouth of the 

Suwannee River is about 1 m. 

Salinity of river water in the 

lower tidal reach increases with 

decreasing flow and proximity 

to the Gulf of Mexico. Vertically 

averaged salinity in the river 

near the tree line is typically 

about 5 parts per thousand at 

medium flow.

Land-surface elevation 

and topographic relief in the 

floodplain decrease with proximity to the coast. Elevations 

range from 4.1 to 7.3 m above 

sea level at the most upstream 

riverine transect and from 0.3 to 

1.3 m above sea level on lower 

tidal transects. Surface soils in 

the riverine reach are predominantly mineral and dry soon 

after floods recede except in 

swamps. Surface soils in upper 

and lower tidal reaches are predominantly organic, saturated 

mucks. In the downstream part 

of the lower tidal reach, conductivities of surface soils are high 

enough (greater than 4 millimhos per centimeter) to exclude 

many tree species that are intolerant of salinity.

Species richness of canopy and subcanopy plants in 

wetland forests in the lower 

Suwannee River is high compared to other river floodplains 

in North America. A total of 

77 tree, shrub, and woody vine 

species were identified in the 

canopy and subcanopy of 
2 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

floodplain wetland forests 

(n = 8,376). Fourteen specific 

forest types were mapped using 

digitized aerial photographs, 

defined from vegetative sampling, and described in terms of 

plant species composition. For 

discussion purposes, some specific wetland types were combined, resulting in three general 

wetland forest types for each 

reach.

Riverine high bottomland 

hardwoods have higher canopy 

species richness than all other 

forest types (40-42 species), 

with Quercus virginiana the 

most important canopy tree by 

basal area. The canopy composition of riverine low bottomland hardwoods is dominated by 

five species with Quercus laurifolia the most important by 

basal area. Riverine swamps 

occur in the lowest and wettest 

areas with Taxodium distichum

the most important canopy species by basal area. Upper tidal 

bottomland hardwoods are differentiated from riverine forests 

by the presence of Sabal palmetto in the canopy. Upper tidal 

mixed forests and swamps are 

differentiated from riverine forests, in part, by the presence of 

Fraxinus profunda in the canopy. Nyssa aquatica, the most 

important canopy species by 

basal area in upper tidal 

swamps, is absent from most 

forests in the lower tidal reach 

where its distribution is probably restricted by salinity. 

Hydric hammocks, a wetland 

type that is rare outside of Florida, are found in the lower tidal 

reach and are flooded every 

1-2 years by either storm surge 

or river floods. Lower tidal 

mixed forests and swamps have 

continuously saturated muck 

soils and are differentiated from 

upper tidal forests, in part, by 

the presence of Magnolia virginiana in the canopy. Lower 

tidal swamps have the highest 

density of canopy trees (about 

1,200 trees per hectare) of all 

floodplain forest types, with 

Nyssa biflora the most important canopy species by basal 

area.

Water use in the Suwannee River basin in Florida and 

Georgia is expected to increase 

over time because of anticipated 

growth and development in the 

region and adjacent areas. If 

increased water consumption 

reduced river flow, river stage 

would decrease and salinity 

would increase, resulting in a 

variety of impacts on forest 

composition, wetland biogeochemical processes, and fish 

and wildlife habitat. 

Forest composition in the 

floodplain is primarily determined by duration of inundation 

and saturation, depth and frequency of floods, and salinity. 

Long-term flow reductions 

would result in shallower flood 

depths, allowing drier and more 

tidal species to invade wetland 

forests of the riverine and upper 

tidal reaches. If flows were 

reduced 2.8-56 m3

/s (100-

2,000 ft3

/s), an estimated 52-

1,140 ha, respectively, would 

change to a drier forest type, and 

36-788 ha, respectively, would 

change to a more tidal forest 

type. The greatest impacts 

would occur in swamps, where 

important swamp species such 

as Taxodium distichum and 

Nyssa aquatica could have 

increased competition not only 

from drier or more tidal species, 

but also from opportunistic bottomland hardwoods or invasive 

exotic species. Reduced flows 

could also result in a conversion 

of some wetland forests to 

uplands, increasing vulnerability to human disturbance, and 

decreasing tree basal area, species richness, and diversity of 

wildlife habitat.

Salt-intolerant species 

would move upstream if flow 

reductions increased salinity in 

the lower tidal reach. If flows 

were reduced 2.8-56 m3

/s (100-

2,000 ft3/s), the area of forests 

along the tree line that would 

convert to marshes is estimated 

to be 72-618 ha, respectively. 

Loss of forests at the tree line 

would result in a loss of complex vertical structural diversity 

and woody micro-habitats that 

are used by many animals. 

These changes are already 

occurring due to sea level rise, 

but changes would occur more 

quickly if salinities increased as 

a result of flow reductions. 

The amount of inundated 

and saturated area in the floodplain forest of the riverine reach 

would decrease if flows were 

reduced. The greatest impacts 

would result from flow reductions that occurred at low flows, 

when inundated and saturated 

areas in the floodplain are limited. Drier conditions would 

result in oxidation of organic 

matter in swamp soils, which 
Introduction 3

would reduce the soil’s waterholding capacity and ability to 

retain water during droughts. 

Drier soils would increase vulnerability of the floodplain to 

fire and could also reduce the 

ability of riverine forests to 

remove nitrates and other pollutants from river water. Loss of 

inundated areas resulting from 

flow reductions at low flow 

would eliminate aquatic habitats 

that are critical to the survival of 

floodplain fishes and aquatic 

invertebrates, and are important 

to many other animals that use 

the floodplain. If flow reductions 

occurred during high flows, 

main channel fishes could 

decrease in diversity and abundance because they are seasonally dependent on flooded 

forests for food, shelter, and 

reproduction. In addition, 

aquatic organisms in the river 

and estuary could be adversely 

affected because they depend on 

particulate organic detritus and 

other floodplain exports as food 

sources.

INTRODUCTION

Wetlands in river floodplains 

perform many vital functions in 

maintaining regional ecological 

integrity. Floodplain wetlands 

absorb and retain floodwaters, ameliorating the effects of both floods 

and droughts, and improve water 

quality by removing pollutants. 

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

and dissemination of plants, and a 

supply of nutrients to aquatic 

organisms in rivers and estuaries. 

The benefits of protecting and 

maintaining healthy floodplain 

ecosystems have been described by 

many authors in the scientific community (Brinson and others, 1981; 

Clark and Benforado, eds., 1981; 

Wharton and others, 1982; Davis 

and others, 1996; Messina and 

Conner, eds., 1998; Mitsch and 

Gosselink, 2000).

Hydrology is generally recognized as the most important factor determining the structure and 

ecological processes in wetlands 

(Greeson and others, eds., 1979; 

Gosselink and others, eds., 1990; 

Lugo and others, eds., 1990; Carter, 

1996). Hydrologic changes due to 

agricultural drainage have been the 

primary cause of wetland degradation and loss in the United States 

(Dahl, 1990). Florida has lost 

about one-half of its wetlands over 

the last 150 years, primarily 

because they have been drained for 

agricultural and urban development (Darst and others, 1996). 

Long-term hydrologic changes alter 

wetland vegetation and soils and 

degrade valuable wetland functions.

Protecting wetlands from significant change due to hydrologic 

alterations is an important goal of 

water managers in the Suwannee 

River basin. Florida law directs 

water management districts to use 

the best available information to 

establish minimum flows and levels 

for watercourses in their districts 

(Chapter 373.042, Florida Statures). The need for preservation of 

existing ecological systems and 

their functions should be considered in establishing minimum flows 

and levels; however, water requirements of wetlands are not well 

defined in most areas. Information 

on long-term hydrologic conditions, soils, and vegetative communities in the forested floodplain 

along the lower Suwannee River is 

needed to gain a better understanding of hydrologic requirements for 

the maintenance of existing wetland 

ecosystems in the basin. Because 

the character of the lower Suwannee River floodplain gradually 

changes from riverine forests 

upstream to tidal forests near the 

coast, innovative study techniques 

are required to address the complexities inherent in this unique 

wetland ecosystem. 

Purpose and Scope

The overall objective of this 

report, to describe hydrologic conditions, soils, and vegetation of the 

forested floodplain in relation to 

river flow of the lower Suwannee 

River, Florida, has five major components:

1. To describe long-term flow and 

stage characteristics of tidal and 

non-tidal reaches of the lower 

Suwannee River. 

2. To describe the hydrology, 

topography, and soils of the 

lower Suwannee River floodplain.

3. To describe and compare floodplain forest types and the distribution of tree species.

4. To relate characteristics of floodplain forests to river flow.

5. To estimate impacts of potential 

river-flow reductions on the 

forested floodplain.

The study area is the forested 

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). Data collection 

began in August 1996 and continued through November 1999. 

Data analysis was completed in 

September 2000.
4 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

Acknowledgments

This project was jointly 

funded by the Suwannee River 

Water Management District 

(SRWMD) and the U.S. Geological Survey (USGS). The authors are 

grateful to John Good and Rob 

Mattson, SRWMD, and Gary 

Mahon, USGS, for extensive technical and administrative guidance 

in all phases of the project from its 

inception to the final publication; 

and to Wade Bryant (USGS) and 

Barbara Kleiss (U.S. Army Corps 

of Engineers) for valuable technical 

Albany

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.

guidance in research design 

throughout the project and for 

review of the final manuscript.

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.

The authors are indebted to 

many people who contributed 

invaluable assistance with field 

work, foremost among them being 

Rob Mattson and John Good, 

SRWMD; and Lani Webster, 

volunteer. The following individuals 

also helped with field work: Angus 

Gholson, Duncan Johnson, Jill 

Pittman, Donald Foose, Venu 

Oddiraju, Robert Tighe, and Sara 

and Melanie Leitman, volunteers; 

Henry Sansing, Russ Langford, 

Kenny McCain, Kendall Smith, 

Larry Smith, and Steve Stump, 

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 (FFWCC); Kay 

Anderson, Natural Resources Conservation Service (NRCS), U.S. 

Department of Agriculture (USDA); 

Joann Mossa, University of Florida; 

Christine Sutter, Eric Lewis, Kelly 

Chancey, and Susie Hetrick, 

SRWMD; Gary Mahon, Rosemary 

McKenney, Agustin Sepulveda, Hal 

Davis, Ed Oaksford, Donald Mark 

Stephens, Mike Solomon, and Mike 

Mokray, USGS. 

The authors would like to 

acknowledge the National Soil 

Survey Center, NRCS, USDA, for 

laboratory analyses of soil salinity, 

and Dennis Nettleton of their staff 

for assistance in interpreting the 

results of their analyses. Appreciation is extended to Kevin Farmer, 

volunteer, for assistance with soils 

data analysis; to John Good, 

SRWMD; Larry Bohman, Marvin 

Franklin, Jack W. Grubbs, Gina 

Tillis, and Stewart Tomlinson, 

USGS, for assistance with hydrologic data analysis; and to Leonard 

Robinson, Stephanie Clark, and 

Ramona Turner, USGS, for assistance with report production. Land 

elevation survey data were collected by Bailey, Bishop, and 
Introduction 5

Lane, Inc; Florida Department of 

Environmental Protection; and 

Ellen Raabe, USGS.

The authors are grateful to the 

following USGS employees: Sandra 

Cooper, Jane Eggleston, Teresa 

Embry, Jerry Giese, Phil Greeson, 

and Shaun Wicklein for technical 

and editorial reviews; Agustin 

Sepulveda for geographic information systems (GIS) assistance; Jim 

Tomberlin and Ron Spencer for 

graphics; Twila Wilson for editing; 

and Pat Mixson for layout.

Setting

The Suwannee River flows 

394 kilometers (km) from its headwaters in the Okefenokee Swamp to 

the Gulf of Mexico (fig. 1). Three 

major tributaries, the Alapaha, 

Withlacoochee, and Santa Fe 

Rivers, drain into the Suwannee 

River, which has a drainage basin 

of approximately 25,770 square 

kilometers (km2

). The drainage 

basin covers portions of the Gulf 

Coastal Plain in central southern 

Georgia and central northern 

Florida (Berndt and others, 1996). 

The Suwannee River is the second 

largest river in Florida with an 

estimated average discharge of 

295 cubic meters per second (m3

/s) 

or 10,540 cubic feet per 

second (ft3

/s) near the mouth 

(Franklin and others, 1995).

The glossary at the beginning 

of this report explains unfamiliar 

terms or terms that have a specific 

meaning in this report that may differ from normal usage. In this 

report, 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. River kilometers (rkm) are used to 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′′. Flow ranges used in 

this report refer to flows at the 

upstream end of the study area. 

Low flows are less than 120 m3

/s 

(4,300 ft3

/s), medium flows range 

from 120 to 297 m3

/s (4,300-

10,590 ft3

/s), and high flows are 

greater than 297 m3

/s (10,590 ft3/s). 

All flow values refer to the combined flow of the Suwannee River 

at Branford and the Santa Fe River 

near Fort White, unless otherwise 

indicated.

Stream characteristics in the 

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

features in the floodplain. The 

lower Suwannee River flows 

through the Gulf Coastal Lowlands 

physiographic region (Puri and Vernon, 1964). Limestone 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. Although the 

average annual precipitation (1961-

90) at Cross City is 146 centimeters 

(cm) (Owenby and Ezell, 1992), the 

surface drainage pattern is poorly 

developed because about 73 percent 

of the precipitation evaporates or 

percolates into the ground (Franklin 

and others, 1999). Surface-water 

streams in the non-tidal portion of 

the river are fed predominantly by 

springs rather than from surface 

runoff (Crane, 1986). Tidal creeks 

are found 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 in the lower Suwannee River 

region is characterized by long, 

humid summers. Average summer 

air temperature (June, July, and 

August) is 26.4 °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 commonly in the 

growing season than in the dormant 

season.

In this report, the term floodplain refers to the 10-year floodplain of the lower Suwannee River. 

The floodplain area is approximately 18,600 hectares (ha), which 

includes wetland and upland forests but does not include open water 

in the main river channel. 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). 

The floodplain is divided into 

three reaches, riverine (R), upper 

tidal (UT), and lower tidal (LT) 

(fig. 2), because hydrologic conditions, vegetation, soils, and potential impacts of flow reductions 

change with distance from the river 

mouth, and therefore, needed to be 

analyzed separately by reach. The 

exact locations of the reach boundaries were based on differences in 

canopy tree species distribution 

along an upstream to downstream 

gradient. The floodplain from rkm 

37 to 45.2 (which includes the 

MS transect) is a transitional area in 

which the high elevation (bottomland hardwood) forests are part of 
6 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

29°15′

29°30′

29°45′

30°00′

83°15′ 83°00′ 82°45′

Old Town

24

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

V1-5

0 4 8 MILES

0 4 8 KILOMETERS

Bell gage

Wilcox gage

Old Town

gage

Fort

White

gage

Branford

gage

Wilcox 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

OBSERVATION SITE

GAGING STATION AND NAME

EXPLANATION

FK

60

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

River, Florida. All 111 verification plots are shown, but only 12 plots referred to in this report are numbered. Data were 

collected at about 150 observation sites, but only 2 sites referred to in this report are shown.
Introduction 7

98

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

V4-12

V4-10

V4-8

SH

SN

KN

KI

TK

V4-24

OS4-19

DM

LK

V3-37

V3-70

V3-33

V3-36

V4-14

V4-9

V4-17

OS4-67

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 °° ° ′′ ′

Old Town

gage

Upper West Pass gage Gopher

River

gage

Fowlers

Bluff

gage

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

River, Florida. (Continued)
8 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

the riverine reach and the low elevation (swamp) forests are part of 

the upper tidal reach. All of the 

lower tidal reach and part of the 

upper tidal reach is in the LSNWR.

Fourteen specific forest type

names and ten general forest type 

names are used throughout this 

report (table 1). Four general forest 

types are combinations of two specific types that are relatively similar, and six general forest types are 

the same as specific types. 

Oak/pine upland forests

(oak/pine) are present on high elevations in the 10-year floodplain 

and are only inundated during the 

highest floods. Many tree species 

present in upland forests cannot 

survive more than brief periods of 

inundation. Bottomland hardwoods (Rblh1, Rblh2/blh3, and 

UTblh) are forests on levees, flats, 

and slopes of floodplains that are 

flooded continuously for several 

weeks or longer every 1 to 3 years, 

and contain tree species adapted to 

periodic inundation and saturation. 

Swamps (Rsw1/sw2, UTsw1/sw2, 

and LTsw1/sw2) are forests in the 

lowest elevations of the floodplain 

that are either inundated or saturated most of the time. Swamps 

contain tree species that have special adaptations for survival in 

anoxic soils. Mixed forests

(UTmix and LTmix) are tidal forest types dominated by a mixture of 

swamp and bottomland hardwood 

or hammock species. Hammocks

(LTham) refer to hydric 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.

Hummocks are mounds 

around the bases of trees that are 

elevated above the surrounding 

ground. Hummocks can be found 

in all forests of the floodplain but 

are most prominent in the lower 

tidal reach. The tree line is the 

east-west line across the lower tidal 

floodplain with primarily forests on 

the upstream side and marshes on 

the downstream side. The tree line 

is the downstream limit of the 

study area.

METHODS OF STUDY

The major components of 

this study were river and floodplain 

hydrology, topography and soils of 

the floodplain, and forest type composition and distribution (fig. 3). 

An analysis of the flow-dependent 

characteristics of the floodplain 

provided the basis for estimating 

impacts of flow reductions on forest 

composition, soil characteristics, 

and aquatic habitats in the floodplain. Analytical methods used in 

this study were not based on a standard model, but were designed to 

address the complexities inherent in 

a forested floodplain that gradually 

changes in character from riverine 

conditions in the upstream part of 

the study area to tidal conditions in 

the downstream part. 

Table 1. Names of forest types in the 10-year floodplain of the lower Suwannee River, Florida

General 

cover type

Reach name

and 

abbreviation

Forest type name and abbreviation

General Specific

Uplands

Riverine (R)

and upper tidal

(UT)

Oak/pine uplands (oak/pine) Oak/pine uplands (oak/pine)

Wetlands

Riverine

(R)

High bottomland hardwoods (Rblh2/blh3) Bottomland hardwoods type 3 (Rblh3)

Bottomland hardwoods type 2 (Rblh2)

Low bottomland hardwoods (Rblh1) Bottomland hardwoods type 1 (Rblh1)

Swamps (Rsw1/sw2) Swamps type 2 (Rsw2)

Swamps type 1 (Rsw1)

Upper tidal

(UT)

Bottomland hardwoods (UTblh) Bottomland hardwoods (UTblh)

Mixed forests (UTmix) Mixed forests (UTmix)

Swamps (UTsw1/sw2) Swamps type 2 (UTsw2)

Swamps type 1 (UTsw1)

Lower tidal

(LT)

Hammocks (LTham) Hammocks (LTham)

Mixed forests (LTmix) Mixed forests (LTmix)

Swamps (LTsw1/sw2) Swamps type 2 (LTsw2)

Swamps type 1 (LTsw1)
Introduction 9

Estimated impacts of

flow reductions on floodplain

Flow-dependent characteristics

of floodplain forest

Forest type

distribution

Forest type

composition

Hydrology of floodplain

Floodplain soils Floodplain

topography

Long-term flow and stage of

tidal and non-tidal river

ANALYSIS

HYDROLOGY

VEGETATION

TOPOGRAPHY

AND SOILS

EXPLANATION

Figure 3. Basic study 

components and analytical 

approach for describing 

hydrology, vegetation, and 

soils of the floodplain and 

estimating impacts of flow 

reductions in the lower 

Suwannee River, Florida.

Data Collection 

The types of data obtained 

during this study included hydrologic measurements, land-surface 

elevations, latitude and longitude, 

soil profile descriptions, soil moisture observations, soil and water 

conductivities, and species identification and size of canopy and subcanopy plants. Data collection 

began in August 1996 and was 

completed in November 1999. 

Study Sites

The floodplain boundary of 

the study area in the riverine and 

upper tidal reach is the 10-year 

floodplain digitized by SRWMD 

from unpublished map data prepared during a Suwannee River 

flood study by the U.S. Army Corps 

of Engineers (1989). The floodplain boundary in the lower tidal 

reach was determined by connecting the downstream limit of the 10-

year floodplain boundary along 

roads to the drainage basin boundary near the mouth (U.S. Geological Survey, 1974). The downstream 

limit of the study area was the tree 

line.

Three types of study sites 

were used for data collection. 

Transects were used for intensive 

collection of data including landsurface elevations, hydrologic conditions, vegetation, and soils. Verification plots were used to collect 

quantitative vegetation data to verify forest type mapping signatures 

on aerial photographs. Observation 

sites were used to obtain additional 

non-quantitative vegetation data to 

verify mapping signatures or to collect additional soils data. Locations 

of all transects, all verification 

plots, and selected observation sites 

are shown in figure 2.

Transects.-- Twelve belt 

transects with a total length of 

about 4,600 meters (m) and 

covering a total area of nearly 

33,000 square meters (m2

) were 

established in the lower Suwannee 

River floodplain (table 2). Each 

transect varied in width from 5 to 

13 m and in length from 53 to 

1,009 m. Transects were 10 to 13 m 

wide where less than 400 m long 

and usually 5 m wide on longer 

transects. Detailed descriptions of 

transect locations with information 
10 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

on access and landowners are presented in another report (Lewis and 

others, 2002). Forest types were 

commonly differentiated in zones 

parallel to the river; therefore, most 

transects were located perpendicular to the river to adequately sample vegetation occurring near the 

center and in transitional areas near 

the edges of each forest type zone. 

Two transects were located in 

homogeneous forests for the purpose of sampling that specific forest type (SN and SH). Location, 

length, and compass bearings of 

transects were predetermined on 

aerial photographs and then located 

on the ground. Transects were 

marked about every 30 m with 

numbered wooden stakes and horizontal distances were measured 

using meter tapes (fig. 4).

Transects were visited many 

times throughout the data collection period to gather information 

about: (1) latitude and longitude, 

(2) land-surface elevations, (3) vegetation, (4) water levels in the 

floodplain and river, (5) soil moisture, and (6) soil profile characteristics. In addition, soil samples 

were collected at all lower tidal 

transects for conductivity analysis, 

and field conductivities of surface 

water were measured at some tidal 

transects. 

The latitude and longitude of 

transect endpoints and some stake 

locations were determined by using 

a Precise Lightweight Global 

Positioning System Receiver

(PLGR) that had a typical accuracy under tree cover of 6 to 15 m 

horizontally. Multiple positions 

were collected on several field visits, and then averaged or otherwise 

reconciled before locations of 

transects were finalized in GIS 

coverages. 

Land-surface elevations were 

determined approximately every 

5 m along transects by using a 

tripod-mounted level and graduated rod (fig. 5). Transects were 

Table 2. Location and sampling area of transects and verification plots in the lower Suwannee River floodplain, Florida

[Sampling area is not shown for subcanopy plants on verification plots, because subcanopy species were recorded at those sites for presence/absence only. 

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 Subcanopy plants

Area 

sampled, in 

m2

Number 

of plants 

sampled

Area 

sampled, 

in m2

Number of 

plants 

sampled

Riverine

Confluence CF 104.3 441.0 4,400 293 2,200 557

Log Landing LL 77.6 921.2 4,606 189 4,606 330

Falkenburry FK 64.4 362.6 2,570 233 1,813 458

Manatee Springs (blh) MS 42.5 414.11 3,330 145 2,478 112

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

Upper

Tidal

Manatee Springs (sw) MS 42.5 594.91 4,189 392 2,975 271

Keen KN 31.2 734.1 3,709 329 3,447 369

Keen Island KI 31.2 100.0 1,000 21 500 97

24 verification plots 23.0 - 36.5 9,824 771

Lower

Tidal

Turkey Island TK 19.8 411.9 2,056 201 824 36

Sandfly North SN 13 88.3 1,148 110 441 64

Sandfly Hammock SH 12.6 151.0 1,510 102 755 48

Barnett Creek BC 11.3 215.6 2,126 235 1,078 91

Lock LK 5.1 145.5 1,455 184 394 163

Demory DM 4.8 53.2 532 86 266 79

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

Subtotal for transects 4,633.4 32,631 2,520 21,777 2,675

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

Total 3,624.4 82,019 5,9012 21,777 2,6752

1

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

2

The total number of canopy and subcanopy plants sampled is 8,576. This includes 8,376 plants from wetland forest types and 200 plants from upland 

forest types.
Introduction 11

surveyed to known benchmarks to 

establish land-surface elevations in 

meters above sea level (Bailey, 

Bishop, and Lane, Inc, written commun., 1999). Land-surface elevations were estimated beyond the 

transect endpoints to understand 

general topographic characteristics 

of the transect area, but were not 

used in any quantitative analyses. 

Figure 4. Measurement of horizontal distances with meter tape extended between

numbered wooden stakes in UTswl forest on MS transect in the lower Suwannee 

River floodplain, Florida.

Figure 5. Surveying with a tripod-mounted level in LTsw2 forest on TK transect 

in the lower Suwannee River floodplain, Florida.

They included approximate elevations between separate parts of a 

transect, and slopes down to the 

river channel, up to the adjacent 

upland, or to adjacent topographic 

features.

Verification plots.-- A total 

of 111 verification plots ranging 

from 20 to 26 m in diameter and 

totaling about 49,000 m2

 in area 

were established in the lower 

Suwannee River floodplain 

(table 2). Minimum sampling areas 

of 314 m2

 for swamp forest types 

and 531 m2

 for bottomland hardwood and upland forests were used 

for verification plots. Sampling 

area was determined by a modified 

nested-plot analysis (MuellerDombois and Ellenberg, 1974). 

Swamp forests usually have fewer 

canopy species and are more 

homogeneous than bottomland 

hardwoods forests, thus the plot 

size required for adequate sampling 

was smaller for swamps than for 

bottomland hardwoods.

Most verification plots were 

visited only once to identify and 

measure canopy species, identify 

subcanopy species, and record latitude and longitude for mapping signature verification. In addition, soil 

moisture observations were 

recorded at every verification plot, 

and soil samples were collected at 

selected plots in the lower tidal 

reach for conductivity analysis.

Coordinates for the centers of 

possible verification plots were 

obtained from GIS aerial photographic images and then located in 

the field using 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 

PLGR under forest cover. Some 

verification plots were located by 

pacing from known starting points. 

The centers of the verification plots 

were marked and then circular plots 

were established using flagging and 

meter tapes. Plots with recent tree 

falls, roadbeds, or other obvious 

alterations were not used.

Observation sites.-- About 

150 observation sites were located 

as needed to obtain additional data. 
12 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

At most observation sites, the most 

prevalent canopy tree species were 

recorded (without quantitative 

sampling) to check forest type signatures on aerial photographs. At a 

few observation sites, soils were 

described or soil samples were collected for conductivity analysis. 

Locations of observation sites are 

not shown on figure 2 except for 

sites OS4-19 and OS4-67, which 

are specifically referenced in this 

report.

Hydrologic Measurements

Flow and stage measurements obtained from eight continuous-record surface-water gaging 

stations were used in this report 

(table 3). Most of the flow data 

were derived from two stations, the 

Suwannee River at Branford and 

the Santa Fe River near Fort White, 

shown in figure 2. All other stations were used primarily to provide stage data.

Water levels were measured 

in selected surface-water features 

(pools, sloughs, and creeks) and in 

the Suwannee River at each 

transect using reference points 

(RPs). Nails driven into trees and 

surveyed to elevation above sea 

level served as RPs. Approximately 

400 water-level measurements 

were made at the transects during 

repeated visits under varying 

hydrologic conditions.

Field conductivity of water 

was measured in a variety of 

surface-water features in the floodplain of the lower tidal reach. 

About 50 measurements were 

made during repeated visits under 

varying hydrologic conditions.

About 600 soil moisture 

observations (dry, saturated, or 

inundated) were made for the upper 

6 cm of the land surface approximately every 30 m along transects 

during repeated visits under varying hydrologic conditions, and during one-time visits to verification 

plots. Saturation of soils was determined by firmly squeezing a handful of soil. If free water could be 

squeezed out, then the soil was 

considered saturated.

Table 3. Surface-water gaging stations used in hydrologic analyses of the lower Suwannee River, Florida

[A break in the record is indicated only when periods of missing record exceed 1 year. rkm, river kilometers; USGS, U.S. Geological Survey; SRWMD, 

Suwannee River Water Management District]

Station name and number Agency

Distance 

upstream of 

mouth of 

Suwannee 

River, in rkm

Period of record

Type of record

used in this

report

Santa Fe River near Fort White,

02322500 USGS 135.5 Oct 1927 to Jan 1930June 1932 to Sept 1999 Daily mean flow

Suwannee River at Branford,

02320500 USGS 122.5 June 1931 to Sept 1999 Daily mean stage and flow

Suwannee River near Bell,

02323000 USGS 90.9

June 1932 to Nov 1956 Daily mean stage and flow

Oct 1996 to Jan 1999 Daily mean stage

Suwannee River near Wilcox,

02323500 USGS 53.8

Oct 1930 to Oct 1931

Mar 1941 to Feb 1951 Daily mean stage

Feb 1951 to Feb 1986 Daily mean stage and flow

Feb 1986 to Sept 1999 Hourly stage and daily mean 

flow

Suwannee River near Old Town,

02323570 USGS 37.8 Oct 1970 to Feb 1986 Daily mean stage 

Feb 1986 to Sept 1999 Hourly stage

Suwannee River at Fowlers Bluff,

02323590

USGS

SRWMD 24.5 Sept 1996 to Sept 1999 Hourly stage

Suwannee River at mouth of 

Gopher River, 291940083061600 SRWMD 9.1 Oct 1979 to Oct 1992

Dec 1993 to Sept 1999 Stage at 15 minute intervals

West Pass Suwannee River at

Suwannee1

, 291930083082800 USGS 4.5 Aug 1995 to Sept 1999 Stage at 15 minute intervals

1

Referred to as Upper West Pass gage in this report.
Introduction 13

Soil Sampling

A total of 96 borings were 

made along transects to sample all 

forest types. The number of borings 

per transect ranged from 8 to 13 on 

the longer transects and from 3 to 6 

on the shorter transects. Soils were 

sampled primarily using a 7.5-cmdiameter bucket auger (fig. 6); however, a few borings were sampled 

by using a 2.5-cm-diameter coring 

tube sampler or a 270-cm-long 

muck probe. Profiles were 

described from the soil surface to 

depths of 1.5 to 2 m unless prohibited by sand caving on top of the 

auger bucket or other impediments. 

Approximate taxonomic soil classifications were determined based on 

the latest revision of Keys to Soil 

Taxonomy (U.S. Department of 

Agriculture, 1999).

A total of 21 surface and 

11 subsurface soil samples were 

collected at 21 locations in lower 

tidal forest types for electrical 

conductivity analysis by the Soil 

Survey Laboratory, National Soil 

Survey Center, Lincoln, Nebraska. 

Figure 6. Examination of soil auger contents in UTsw2 forest at KN transect in 

the lower Suwannee River floodplain, Florida. Crinum americanum dominates the 

ground-cover at this site.

The saturated-paste method of 

determining soil conductivity was 

used for large volume soil samples, 

and the salt-prediction method was 

used for small volume soil samples 

(U.S. Department of Agriculture, 

1996).

Vegetation Sampling

A total of 5,901 canopy 

plants were identified to species 

and measured for diameter at 

breast height (dbh) on belt 

transects and verification plots 

(fig. 7). The total canopy sampling 

area was 82,019 m2

 (table 2). Canopy plants included all woody 

plants with a stem diameter of 

10 cm or greater and a height of 

3 m or taller. The dbh of trees with 

swollen bases were measured for 

diameter above the swelling. Basal 

area (stem cross-sectional area) 

was computed from dbh, and density was determined from the number of trees. Canopy trees with 

multiple trunks were counted as 

one tree, with all trunks having a 

diameter greater than 4 cm measured for dbh; basal areas for these 

trees were the sum of the basal 

areas of individual trunks. Trees 

with multiple trunks were considered canopy trees if any single 

trunk had a dbh of 10 cm or greater. 

A total of 2,675 subcanopy 

plants were identified to species 

and measured for dbh on belt 

transects ranging from 2 to 10 m in 

width. The total subcanopy sampling area was 21,777 m2

. In 

addition, subcanopy plants on 

111 verification plots were identified to species and recorded for species presence only. Subcanopy 

plants included all woody plants 

with a dbh of 2 to 9.9 cm and a 

height of 3 m or greater. Subcanopy 

trees with multiple trunks were 

counted as one individual.

Plant nomenclature used in 

this report follows that of Godfrey 

(1988), unless otherwise indicated. Common names of all plant 

species are listed in the front of this 

report. Names of varieties have 

been omitted in the body of the 

report, but are included in the plant 

list in the front of the report.

This report does not include 

ground-cover vegetation data. 

Approximately 300 ground-cover 

species that were sampled at transects 

and verification plots during the study 

period are described and analyzed by 

forest type in another report (Darst 

and others, 2002).

Data Analysis

Long-Term River Flow and Stage

Analysis of both river flow 

and stage was necessary to relate 

the hydrology of the floodplain to 

the river. Hydrologic conditions at 

floodplain transects are directly 

related to stage in the river channel 

adjacent to each transect. However, 
14 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

flatter near the coast, and 3) the 

period of record could vary greatly 

from one gage to another if stage 

data were determined from the 

nearest gage. Flow, on the other 

hand, is relatively consistent 

throughout the riverine reach under 

most conditions, and throughout the 

upper tidal reach under non-tidal 

conditions at high flows. Thus, relations of floodplain conditions to 

flow can be compared among 

transects in those two reaches of the 

river. In this report, calculations of 

river stage and floodplain conditions at riverine transects under all 

flow conditions and upper tidal 

transects during high flows were 

related to long-term flow records at 

the upstream end of the study area. 

Hydrologic conditions in the floodplain at upper tidal transects during 

low and medium flows and lower 

tidal transects under all flow conditions were related to stage records 

from upper and lower tidal gages. 

Flow. -- The primary longterm record used in this report is the 

combined daily mean flow of the 

Suwannee River at Branford and the 

Santa Fe River near Fort White, 

which herein is referred to as Branford-Fort White flow. Branford-Fort 

White flow generally represents 

Suwannee River flow just below the 

confluence of the Suwannee and 

Santa Fe Rivers. Gains from tributaries or ground water, or losses to 

storage from Branford to the confluence and Fort White to the confluence are not included. Several 

factors were considered in the 

selection of Branford-Fort White 

flow as the primary source for longterm data. Branford-Fort White 

flow represents flow at the 

upstream end of study reach better 

than Branford flow alone, and provides a longer period of record 

(67 years) than exists at the Bell 

gage (23 years) or the Wilcox gage 

(49 years). Also, the quality of 

discharge data at Branford and Fort 

White (good) is better than at Wilcox 

(poor) because of tidal conditions at 

Wilcox (Franklin and others, 1999). 

Based on the period of record for 

Bell (1932-56) and Wilcox (1951-

99), there is an excellent linear 

relation between time-lagged 

Branford-Fort White daily mean 

flows and daily mean flows at these 

relations between floodplain conditions and river stage cannot easily 

be compared between transects or 

summarized by reach for the following reasons: 1) river stages 

decline from the upstream to the 

downstream portion of the study 

area, 2) range in stage decreases as 

the floodplain widens and becomes 

Figure 7. Measuring and identifying canopy trees in UTsw1 forest on MS transect 

in the lower Suwannee River floodplain, Florida.
Methods of Study 15

two downstream stations (Bell, 

time-lag = 1 day, r2

 = 0.99; Wilcox, 

time-lag = 3 days, r2 = 0.98). This 

excellent relation indicates that 

Branford-Fort White flow data can 

be used to reasonably represent 

downstream flow data. Based on 

mean flow for the period of record 

at Bell and Wilcox, there is a 

10 percent increase in flow from 

Branford-Fort White to Bell, and a 

17 percent increase in flow from 

Branford-Fort White to Wilcox.

Long-term flow statistics calculated for Branford-Fort White for 

the period 1933-99 include mean 

monthly flows, recurrence intervals 

for maximum 1-day flow and maximum threshold 14-day flow, and 

flow duration. The maximum 

threshold 14-day flow is the highest 

flow that is equaled or exceeded for 

14 consecutive days during a year. 

The maximum threshold n-day 

flow differs from the more commonly used maximum n-day flow, 

which is calculated from the highest mean flow for n consecutive 

days. These two types of statistics 

are described and compared graphically in figure 17 of Leitman and 

others (1984). Recurrence intervals 

were calculated using log-Pearson 

Type III analysis (Interagency 

Advisory Committee on Water 

Data, 1982). Recurrence intervals 

were computed from annual maximum daily mean flow instead of 

annual maximum instantaneous 

flow because combined instantaneous peaks from the Branford and 

Fort White stations cannot be used 

to represent instantaneous peaks 

just below the confluence of the 

Suwannee and Santa Fe Rivers. 

The difference between the maximum daily mean discharge and the 

instantaneous peak, however, 

appears to be minimal based on a 

difference of less than 1 percent in 

1998 at Branford. Flow duration, 

or percent exceedance, is the total 

percentage of time during which 

specified flows are equaled or 

exceeded in a given period.

Stage.-- Long-term river 

stage data at the transects were 

described using various stage statistics. Due to changes in river hydrology with proximity to the coast and 

availability of river stage data, the 

types of statistics and calculation 

methods varied between reaches 

and sometimes between transects.

At most transects, stage statistics were derived from long-term 

flow statistics. Converting longterm flow data to stage required the 

development of stage-discharge ratings relating stage at each transect 

to time-lagged Branford-Fort White 

flow. Specific methods and source 

data used to develop stage-discharge ratings for each transect are 

described in table 4. Daily mean 

stage ratings were developed for all 

riverine transects (fig. 8). Daily 

high and daily low stage ratings 

were developed for both upper tidal 

transects and one lower tidal 

transect (fig. 9). Daily mean stage 

ratings were not developed at tidal 

transects because conditions in the 

floodplain are better described by 

daily high and low stages than by 

daily mean stage. Daily mean stage 

at a tidal transect may indicate that 

the floodplain floor is not inundated, 

whereas daily high stage may show 

that at least some of the transect is 

covered by water at high tide.

Ratings were created by fitting hand-drawn lines through the 

data points. The fit of these lines to 

the data points was excellent 

(r2 > 0.90) for all riverine and upper 

tidal gage and transect ratings. The 

fit for the daily high rating at TK 

was acceptable (r2

 > 0.70). Because 

of the poor relation between stage 

and flow at the Gopher River gage 

(r2 < 0.70) (fig. 9), ratings were not 

developed for transects downstream 

of TK.

Recurrence interval flood 

stages and stage durations were 

calculated from long-term flow 

statistics and stage-discharge ratings at all riverine and upper tidal 

transects and one lower tidal 

transect (top half of table 5). Stage 

durations (percent exceedance) 

were not calculated for KN, KI, 

and all lower tidal transects 

because durations do not adequately describe the daily tidal 

fluctuations that control hydrologic conditions most of the time 

at these transects.

Median monthly high stage 

(MMH), median daily high stage 

(MDH), and median daily low 

stage (MDL) were calculated to 

describe typical monthly and daily 

stages at upper and lower tidal 

transects, including the MS 

transect, which has both riverine 

and tidal forest types (bottom half 

of table 5). These statistics are similar to traditional tidal datums in use 

by the National Oceanic and Atmospheric Administration (mean high 

water springs, mean higher high 

water, and mean lower low water 

(International Marine, 1995)), 

which could not be calculated and 

were not appropriate for use here 

because of the mixed influence of 

river flow and tide. MMH, MDH, 

and MDL were calculated directly 

from estimated stage data; their 

relation to river flow was not determined. Stage statistics were not 

determined for the BC transect 

because it is too far from the river 

to estimate transect water levels 

from river stage. 

Two other types of hydrologic data were calculated for this 

report, but are not included in
16 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

table 5. The stage of the 1948 

flood at all lower tidal transects 

was derived from flood profiles 

developed by the U.S. Army 

Corps of Engineers (1974). 

Storm surge elevations were 

estimated by linear interpolation 

between gages, or extrapolation 

downstream from Gopher River 

gage using adjustments for stage 

increases based on the Hurricane Josephine (October 7 and 8, 

1996) and Hurricane Earl (September 3, 1998) storm surges 

recorded at Upper West Pass gage.

Table 4. Methods and source data used to develop stage-discharge ratings at transects in the lower Suwannee River 

floodplain, Florida

[All stage-discharge ratings were developed by fitting a hand-drawn line through the data points. Stage-discharge ratings are based on the period of record 

that is common to both gages used for interpolation. See table 3 for period of record for individual gages]

Reach Transect 

name

Location, 

in rkm

Type of 

rating 

developed

Source of stage discharge rating

Fit of rating 

to data 

points (r2 Method )

Stage data plotted in 

relation to Branford-Fort 

White flow

Time-lag1

, 

in days

1

 Time-lag applied to Branford-Fort White flow data.

Riverine

CF 104.3 Daily mean 

stage

Linear interpolation between 

2 gage ratings

Branford daily means 0 0.99

Bell daily means 1 0.98

LL 77.6 Daily mean 

stage

Linear interpolation between 

2 gage ratings

Bell daily means 1 0.98

Wilcox daily means 3 0.98

FK 64.4 Daily mean 

stage

Linear interpolation between 

2 gage ratings

Bell daily means 1 0.98

Wilcox daily means 3 0.98

MS (blh) 42.5 Daily mean 

stage

Linear interpolation between 

2 gage ratings

Wilcox daily means 3 0.98

Old Town daily means 4 0.95

Upper

tidal

MS (sw) 42.5

Daily high 

stage

Linear interpolation between 

2 gage ratings

Wilcox daily highs 3 0.98

Old Town daily highs 4 0.94

Daily low 

stage

Linear interpolation between 

2 gage ratings

Wilcox daily lows 3 0.98

Old Town daily lows 4 0.96

KN

(and KI) 31.2

Daily high 

stage

Transect rating developed 

directly from estimated KN 

daily high stages

KN daily highs estimated 

by linear interpolation 

between Old Town and 

Gopher River daily highs

4 0.90

Daily low 

stage

Transect rating developed 

directly from estimated KN 

daily low stages

KN daily lows estimated 

by linear interpolation 

between Old Town and 

Gopher River daily lows

4 0.96

Lower

tidal

TK 19.8

Daily high 

stage

Transect rating developed 

directly from estimated TK 

daily high stages

TK daily highs estimated 

by linear interpolation 

between Old Town and 

Gopher River daily highs2

2

 Slight adjustments to stages were made based on 3 years of data from the Fowlers Bluff gage that indicated a change in the slope of the river surface 

between Old Town and Gopher River gages.

5 0.74

Daily low 

stage

Transect rating developed 

directly from estimated TK 

daily low stages

TK daily lows estimated 

by linear interpolation 

between Old Town and 

Gopher River daily lows2

5 0.90

SN 13

No ratings developed due to poor relation between stage at 

these locations and Branford-Fort White flow

SH 12.6

BC 11.3

LK 5.1

DM 4.8
Methods of Study 17

0

2

4

6

8

10

12

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

FLOW, IN CUBIC METERS PER SECOND

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000

FLOW, IN CUBIC FEET PER SECOND

DAILY MEAN RATING

Old Town gage r =0.95 2

Wilcox gage r =0.98 2

Bell gage r =0.98 2

Branford gage r =0.99 2

CF transect

LL transect

FK transect

MS transect

ELEVATION, IN METERS ABOVE SEA LEVEL

-1

0

1

2

3

4

5

6

7

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

FLOW, IN CUBIC METERS PER SECOND

0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000

FLOW, IN CUBIC FEET PER SECOND

DAILY HIGH RATING

DAILY LOW RATING

MS transect

OldTown gage r 2=0.94 (high) r 2=0.96 (low)

TK transect r 2=0.74 (high) r 2=0.90 (low)

Gopher River gage r 2=0.08 (high) r 2 =0.64 (low)

W x ga

ilco g =0. e r 2 98 (high) r 2= .9 (l 0 8 ow)

KN transect r 2=0.90 (high) r 2=0.96 (low)

ELEVATION, IN METERS ABOVE SEA LEVEL

Figure 9. Daily high and low stage at gages and tidal transects in relation to flow in the lower Suwannee River, 

Florida. Flow is combined flow of Suwannee River at Branford and Santa Fe River near Fort White.

Figure 8. Daily mean stage at gages and riverine transects in relation to flow in the lower Suwannee River, Florida. 

Flow is combined flow of Suwannee River at Branford and Santa Fe River near Fort White.
18 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Table 5. Methods and source data used to calculate long-term river stage statistics at transects in the lower Suwannee River 

floodplain, Florida

River stage

statistic Methods and source data

Period of 

record 

used

Transects for which statistic was

developed

CFLLFKMS (blh)MS (sw)KN, KITKSNSHBC1

1

Stage statistics were not determined for BC transect because it is too far from the river to estimate transect water levels from river stage.

LK, DM

Maximum 1-day stage 

for 2-year, 5-year, and 

25-year recurrence 

interval floods

Maximum 1-day flow for recurrence interval floods 

at Branford-Fort White converted to stage at 

transect using stage-discharge rating at transect

67 years

1933-99 X X X X X X X

Maximum threshold 

14-day stage for 2-year, 

5-year, and 25-year 

recurrence interval floods

Maximum threshold 14-day flow for recurrence 

interval floods at Branford-Fort White converted to 

stage at transect using stage-discharge rating at 

transect

67 years

1933-99 X X X X X X X

Stage duration (percent 

exceedance)

Flow duration at Branford-Fort White converted to 

stage at transect using stage-discharge rating at 

transect

67 years

1933-99 X X X X X

Median monthly high 

stage (MMH), median 

daily high stage (MDH), 

and median daily low 

stage (MDL)

Calculated 

directly from 

estimated 

daily high 

and low 

stages

Daily high and low stages estimated 

by linear interpolation between Wilcox and Old Town daily high and low 

stages

14 years

1986-99 X X

Daily high and low stages estimated 

by linear interpolation between Old 

Town and Gopher River daily high 

and low stages

13 years

1986-92

1994-99

X X X X

Daily high and low stages estimated 

by extrapolating downstream from 

Gopher River daily high and low 

stages2

2

Adjustments for drop in stage from Gopher River gage to LK and DM transects were estimated using selected data from Upper West Pass Gage and 

flood profiles developed by U.S. Army Corps of Engineers (1974).

19 years

1980-92

1994-99

X

These methods are inadequate for 

making accurate estimates of storm 

surge elevations, therefore these 

elevations are used in this report for 

general comparative purposes only 

and should not be used for any 

other purpose. 

Defining and Mapping Forest 

Types

Methods for defining and 

mapping forest types are described 

in figure 10. Differences in spectral 

signatures on aerial photographs 

were used to select the forest types 

within each reach, with vegetative 

sampling on the ground used to 

define the species composition of 

each type. Reach differences in 

forest type composition were evident from ground sampling, but 

could not be distinguished on aerial 

photographs. Therefore, the reach 

designations for all forest types 

were determined from vegetative 

sampling data alone, using the 

methods described in the final 

mapping section of the flow chart in 

figure 10.

Photographic images used 

for mapping were digital orthophoto quadrangles (DOQ’s), 

which were produced from colorinfrared aerial photographs (scale 

1:40,000) taken in the winter of 

1994 by National Aerial Photography Program that were scanned and 

rectified with 1-m2

-per-pixel resolution by USGS. The entire 10-year 

floodplain was mapped, including 

areas altered for agricultural or residential use that were historically 

forested. Altered areas were classified as wetland or upland forests 

based on proximity and similarity 

to unaltered forest signatures, and 

elevations from topographic contours on USGS quadrangle maps. 

Verification of the map was 

conducted using rules to test the 

canopy composition of mapped forest types (fig. 10). Rules were 

developed using 1) literature 

research to categorize tree species 

as belonging to swamp, bottomland 

hardwood, hammock, or upland 
Methods of Study 19

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

150 observation sites Preliminary rules developed to test the canopy

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 of map finalized

Accuracy of map calculated Total area of polygons for each

of the 14 forest types

Species composition (in relative basal area

and density) described for each of the

14 forest types using data from all transect

and verification plots, as mapped

VERIFICATION

AND FINAL MAPPING

FINAL PRODUCTS

PRELIMINARY MAPPING

(based on 12 transects,

9 verification plots, and

150 observation sites)

(based on 102

verification plots)

Figure 10. Methods for defining and mapping forest types in the lower Suwannee River floodplain, Florida.
20 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

forests (Fowells, 1965; Clark and 

Benforado, eds., 1981; Leitman and 

others, 1984; Reed, 1988; Vince 

and others, 1989; Light and others, 

1993), and 2) relative basal area

(rba) of canopy plant species in 

this study (table 6).

Map verification results 

indicated that 71 percent of specific forest types and 77 percent of 

general forest types were correctly 

mapped (table 7). Incorrectly 

mapped sites were slightly more 

likely to have a wetter forest type 

than the mapped type. Mapping 

accuracy was greater with regard 

to reach designations alone 

(92 percent), with only 8 plots 

having forest compositions that 

did not meet the criteria for that 

reach. The forest types of the 

polygons containing the 102 plots 

used for verification were 

unchanged regardless of actual 

forest composition.

Species composition was 

determined for the canopy and 

subcanopy vegetation of each forest type. The rba and relative 

density (rd) of canopy vegetation 

were calculated using data from all 

transects and verification plots as 

mapped in the forest map. The rd 

of subcanopy vegetation was calculated from transect data only. To 

provide general information about 

the most important tree species in 

wetland forests overall, the rba and 

rd of all species in the riverine and 

tidal reaches were calculated using 

the following methods. The rba of 

each species in each riverine forest 

type was weighted by the relative 

area of the forest type from the forest map, and then combined with 

rba’s from all other forest types in 

the riverine reach. This process 

was repeated for all forest types in 

the upper and lower tidal reaches 

combined, to provide information 

on the most important tidal 

species.

Data from the forest map are 

used in this report in descriptions 

of forest type area and distribution, 

and in analysis of the potential 

impacts of flow reductions; however, the map itself is not presented 

in this report. GIS files of the forest map can be obtained from 

USGS (Tallahassee, Florida) or the 

SRWMD.

Flow-Dependent Characteristics 

Of Floodplain

Conditions in the forested 

floodplain were related to river 

flow based on four hydrologic 

characteristics: inundation, saturation, flood depths, and salinity. 

These four flow-dependent characteristics are important in maintaining a healthy floodplain ecosystem 

and would change if flows were 

reduced. Inundation and saturation in relation to river flow were 

estimated for the riverine forest 

types only. Similar estimates were 

not calculated for tidal forest types 

because hydrologic conditions in 

tidal forests are more dependent on 

tides rather than river flow. Flood 

depths during selected flood events 

were estimated for forest types in 

all reaches. Typical salinities associated with the tree line were estimated in the lower tidal reach.

Methods for calculating the 

area of each riverine forest type 

that is inundated or saturated in 

relation to river flow are described 

in figure 11. Three types of source 

data were used: field observations 

and measurements at transect and 

verification plots, forest types 

from the forest map, and long-term 

hydrologic data from five gaging 

stations. “Result A” in figure 11 

was calculated from direct observations of hydrologic conditions in 

the floodplain. Direct observations were not necessary to calculate “Result B” because at flows 

greater than 396 m3

/s 

(14,000 ft3

/s), inundation of the 

floodplain by the river is unrestricted by levees or other high elevation features and the area 

inundated can be calculated by 

comparing river surface elevations 

with land-surface elevations.

In the analysis of hydrologic data in figure 11, continuous 

flow data were converted to discrete data using flow increments. 

Flow increments were selected for 

Branford-Fort White flows corresponding to stage increments of 

7.6 cm at the Wilcox gage (near 

the center of the study area). This 

resulted in a total of 50 flow increments for flows ranging from 28 to 

873 m3

/s (1,000-31,193 ft3/s). All 

riverine wetland forests are 

flooded at flows in the upper end 

of that range. 

Results in the final box in 

figure 11 were used to create x-y 

line graphs for each riverine forest 

type with Branford-Fort White 

flow on the x axis and inundated or 

saturated area on the y axis. For 

each forest type, flows at which 

the minimum, 25th percentile, 

median, 75th percentile, and maximum area that was inundated or 

saturated were determined. Flows 

were converted to long-term durations using flow duration analysis 

of Branford-Fort White flows 

(1933-99). Box plots were created 

from these duration quartiles and 

ranges to depict durations of inundation and saturation for riverine 

forest types. 
Methods of Study 21

Table 6. Rules for testing mapped forest types at verification plots in the floodplain of the lower Suwannee River, Florida

[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 + Fraxinua 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 hemisphaerica 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.
22 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Flood depths during the 2-

year, 5-year, and 25-year, 14-day 

threshold floods were determined 

for the median elevation of each 

forest type at each transect 

(fig. 12). Recurrence intervals 

were selected to cover the range of 

time (2 to 5 years) that seedlings 

and saplings of the majority of tree 

species are most affected by flooding and to include a longer interval 

(25 years) for larger flood events 

that may be important to a few species. Literature review on seedling 

survival under flooded conditions 

was conducted to select the duration of flooding. Continuous submergence for 10-20 days kills most 

tree seedlings (Demaree, 1932; 

Hosner, 1960). A single duration of 

14 days was selected for impact 

analysis in this report.

Three types of source data 

were used to calculate flood depths: 

land elevation surveys at the 

transects, forest types from the 

forest map, and long-term flow and 

stage data from seven gaging stations. Daily mean stage was used to 

calculate depth of continuous flooding for 14 days at all riverine 

transects, including MS, which is 

tidal only at low and medium flows 

but not during floods. At KN, KI, 

and all lower tidal transects, however, tidal fluctuations occur at high 

flows as well. At those sites, flood 

depths were calculated from daily 

low stage, because depths calculated 

from daily mean stage would not 

represent continuous submergence 

of seedlings for 14 days.

Results were used to graph 

flood depths (in meters) in relation 

to distance from river mouth (in 

kilometers) for each general forest 

type. Flood depths were determined at all transects except BC, 

which is too far from the river to 

estimate transect water levels from 

river stage.

Flood depths during the 2-

year and 5-year, 14-day floods were 

calculated for the minimum, 25th

percentile, 75th percentile, and maximum elevations of each forest type 

in the riverine and upper tidal reach. 

These calculations were made using 

the same methods used to calculate 

flood depths for the median elevations of each forest type in figure 

12. Results for riverine transects 

were combined by averaging flood 

depths of three transects for swamps 

(CF, LL, and FK) and four transects 

for bottomland hardwoods (CF, LL, 

FL, and MS). Results for upper 

tidal forests were based on the KN 

and KI transects only, because all 

types were present at KN and KI but 

not at MS, and KN and KI were 

approximately in the middle of the 

reach. Box plots were created from 

quartiles and ranges of flood depths 

for riverine and upper tidal forest 

types.

Table 7. Mapping accuracy based on tests of forest type rules at verification plots in the floodplain of the lower Suwannee 

River, Florida

Specific forest types General forest types

Forest 

type 

name

Number of 

polygons 

mapped

Verification plots

Forest type 

name

Verification plots

Total 

number 

sampled

Number 

correctly 

mapped

Percent 

correctly 

mapped

Forest types of incorrectly 

mapped plots

Total 

number 

sampled

Number 

correctly 

mapped

Percent 

correctly 

mapped

oak/pine 506 7 5 71 Rblh2, Rblh3 oak/pine 7 5 71

Rblh3 474 10 6 60 Rblh2, oak/pine (3) Rblh2/blh3 21 17 81

Rblh2 491 11 10 91 Rblh1

Rblh1 654 11 9 82 Rsw2, Rblh2 Rblh1 11 9 82

Rsw2 306 7 4 57 Rsw1 (2), Rblh1 Rsw1/sw2 12 11 92

Rsw1 182 5 4 80 Rsw2 

UTblh 202 6 5 83 oak/pine UTblh 6 5 83

UTmix 225 5 2 40 UTsw2 (2), UTblh UTmix 5 2 40

UTsw2 317 7 4 57 Rsw1, UTsw1, LTsw1 UTsw1/sw2 11 9 82

UTsw1 208 4 4 100 none

LTham 204 6 5 83 oak/pine LTham 6 5 83

LTmix 353 7 5 71 UTblh, LTsw2 LTmix 7 5 71

LTsw2 444 8 5 63 UTsw1, UTblh, LTsw1 LTsw1/sw2 16 11 69

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

TOTAL 4,983 102 72 71 TOTAL 102 79 77
Methods of Study 23

EXPLANATION

TOPOGRAPHY

AND SOILS

VEGETATION

HYDROLOGY

HYDROLOGIC ANALYSIS

INUNDATION-SATURATION

ANALYSIS

River stage

measured at

transect at time

of field visit

Land-surface elevations

interpolated for

every meter of transect

Stage-discharge ratings

relating stage at each transect

to Branford-Fort White flow

Land-surface elevation

for each meter of

transect compared to

river stage at each flow

increment to determine

if inundated or not

Water levels

measured at transects

in floodplain ponds

and sloughs

Land-surface elevations

surveyed about every

5 meters at transects

Total area, in

hectares, determined

for each forest type in

riverine reach

Results from all transects averaged for

each flow increment, producing a single

data set of the average percent of each

riverine forest type that is inundated or

saturated at each flow increment

RESULT B

Percent of each forest type that is inundated

at each transect for each flow increment

based on land-surface elevations

FINAL RESULT

Area, in hectares, of each riverine forest type that

is inundated or saturated at each flow increment

RESULT A

Percent of each forest type that is inundated or

saturated at each transect (including nearby

verification plots) for each flow increment

up to 396 m /s (14,000 ft /s) 3 3

based on observed conditions

Soil moisture conditions (dry,

saturated, or inundated)

estimated for every meter of

transect and at each verification

plot for each field visit

For each transect (including nearby

verification plots), XY data points from all field

visits grouped by river stage and averaged

to correct for varying climatic conditions;

XY line drawn through average points

Forest type

determined for every

meter of transect and

each verification plot

Forest type

determined for every

meter of transect

Long-term gage records

(Branford-Fort White flow;

Branford, Bell, Wilcox,

and Oldtown stage)

Field observations of soil

moisture (dry, saturated, or

inundated) made about every

30 meters at transects and

at verification plots

For each transect (including nearby verification plots),

a single set of data points created for each forest type

using data from result A for flow increments

up to 396 m /s (14,000 ft /s) and data from result B

for all remaining higher flow increments, with

saturation for higher flow increments estimated from

saturation observations at lower flow increments

3 3

XY data point created for each field visit date:

Percent of each forest type that is

inundated or saturated (Y) in relation

to river stage at time of field visit (X)

Flows divided into 50 flow

increments; river stage at

transect determined for

each flow increment

Figure 11. Methods for calculating area of each riverine forest type that is inundated or saturated in relation to flow 

in the lower Suwannee River, Florida. 
24 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

DATA FOR 5-YEAR TK

14-DAY STAGES ONLY

EXPLANATION

TOPOGRAPHY

VEGETATION

HYDROLOGY

HYDROLOGIC ANALYSIS

FLOOD DEPTH ANALYSIS

Land-surface elevations

interpolated for

every meter of transect

Stage-discharge ratings

relating daily stage at

, , , and and daily

stage at / and and

to Branford-Fort White flow

mean

low

CF LL FK MS

KN KI TK

Land-surface elevations

surveyed about every

5 meters at transects

River stage associated with

2-year, 5-year, and 25-year

maximum threshold 14-day flows

determined at , ,

, , / , and

CF LL

FK MS KN KI TK

Forest type determined

for every meter of

transect

Long-term daily mean

stages at Branford, Bell,

Wilcox, and Oldtown,

long-term unit value

stages at Oldtown and

Gopher River

Elevations summarized by

forest type and median

elevation calculated for each

forest type at each transect

Recurrence interval analysis

to determine 2-year, 5-year,

and 25-year maximum

threshold 14-day flows for

Branford-Fort White (1933-99)

Long-term unit value

stages at Oldtown and

Gopher River, selected

unit value stages at

Upper West Pass

Estimated daily low stages

at (1986-99) and

(1979-99)

determined by

interpolation or

extrapolation

from nearby gages

SN/SH

LK/DM

Long-term daily

mean flows for

Branford-Fort White

Actual floods in 1992,

1983, and 1998

selected to represent

2-year, 5-year, and

25-year floods,

respectively, by

comparing BranfordFort White annual flood

flows and recurrence

interval statistics

14-day maximum threshold stage for

1992, 1983, and 1998 determined at

and (1983 stage for

determined by interpolation between

5-year maximum threshold 14-day stage

and Gopher River

1983 maximum threshold 14-day stage)

SN/SH LK/DM SN/SH

TK

FINAL RESULT

Median elevation of each forest type at each transect

compared to 2-year, 5-year, and 25-year maximum

threshold 14-day river stages at each transect to determine

FLOOD DEPTH (if river stage is higher than land surface) or

ELEVATION OF RIVER STAGE BELOW LAND SURFACE

(if river stage is lower than land surface)

Figure 12. Methods for calculating flood depths for each forest type at each transect in the lower Suwannee River 

floodplain, Florida. Flood depths were not calculated for BC transect because it is too far from the river to estimate 

transect water levels from river stage.
Methods of Study 25

Literature research was conducted to describe salinity tolerance 

of tree species in the lower tidal 

reach. Typical salinities associated 

with the tree line were determined 

in East and West Pass in relation to 

flow at the Wilcox gage based on 

salinity-flow relations developed by 

Tillis (2000). 

Impacts of Flow Reductions

Impacts of flow reductions 

on floodplain forests were estimated using five hypothetical flow 

reductions, 2.8, 8.4, 14, 28, and 

56 m3

/s (100, 300, 500, 1,000, and 

2,000 ft3

/s), which were selected to 

represent a range of impacts from 

very small to very large. Average 

annual water consumption in the 

Suwannee River basin in 1995 was 

between 9.0 and 9.8 m3

/s (320 and 

350 ft3

/s) based on water withdrawn 

from surface- and ground-water 

sources minus water returns from 

municipal or industrial wastewater 

plants, septic tanks, and irrigation 

percolation (Fanning, 1997; 

Marella, 1999; U.S. Geological 

Survey, 2001; R. Marella, U.S. 

Geological Survey, written commun., 2001). Water consumption in 

the basin increased substantially 

after the early 1980’s primarily due 

to the widespread use of center 

pivot irrigation systems (Pierce and 

others, 1984; Marella, 1995). 

Impact analyses in this report used 

forest types that were based on data 

from canopy trees older than 

20 years of age in most cases, 

which were established during 

earlier conditions with much lower 

water consumption. A trend analysis with an examination of associated climatic differences has not 

been conducted for river flows in 

the lower Suwannee River; therefore, the entire period of record 

(1933-99) was used in the impact 

analyses.

The five hypothetical flow 

reductions were subtracted from the 

daily mean flow of every day in the 

67-year period of record at Branford-Fort White, and then longterm duration and flood frequency 

statistics were recalculated. A consistent decrease in flows throughout 

the reach where the reductions were 

applied was assumed.

Changes in forest composition estimated for hypothetical flow 

reductions were calculated from 

changes in long-term flow statistics 

that were considered to be critical 

to the maintenance of the existing 

forest type. Selection of critical 

flow statistics was based on review 

of scientific literature and analysis 

of data collected in this study 

regarding the hydrologic conditions 

associated with each forest type. 

Estimated impacts from flow reductions were calculated for general 

forest types only, because potential 

changes in general forest types, 

such as conversion of swamps to 

bottomland hardwoods, were considered to be more important than 

changes in specific types that were 

similar, such as conversion of Rsw1 

to Rsw2. Three types of forest composition changes were calculated.

1. Change to a drier forest type. 

The percentage that long-term 

hydrologic statistics of 

Rsw1/sw2 shift toward that of 

the next drier type, Rblh1, was 

calculated for five hypothetical 

flow reductions. This calculation used four critical hydrologic statistics: duration of 

inundation; duration of saturation; 2-year, 14-day threshold 

flood depth; and 5-year, 14-day 

threshold flood depth. The area 

of Rsw1/sw2 estimated to 

change to Rblh1 was calculated 

for each hypothetical flow 

reduction by multiplying the 

percentage change for the 

measure that changed the least 

(5-year flood depths) times the 

total area of Rsw1/sw2. Similar 

calculations using the percentage change in 5-year flood 

depths were made to determine 

the area of four additional forest 

types that were estimated to 

change to the next drier forest 

type.

2. Change to a more tidal forest 

type. Reach boundaries 

(delineating the upstream extent 

of tidal forests) would move 

upstream if flows were reduced 

and flood depths decreased. 

Graphs depicting flood depths 

by rkm for the 5-year, 14-day 

threshold floods were used to 

calculate the estimated distance 

that advancing (more tidal) forest types would move upstream 

and replace retreating (less tidal) 

forest types at the reach boundaries. These distances were calculated for three forest type 

changes and five hypothetical 

flow reductions. The areas of 

forest types affected by reach 

boundary movements were calculated from the forest map for 

each flow reduction.

3. Conversion of forest to marsh at 

the tree line. Typical salinities 

associated with the tree line 

would move upstream if flows 

were reduced. Multiple linearregression models developed by 

Tillis (2000) were used to determine the new upstream location 

of tree line salinities for five hypothetical flow reductions at the 

Wilcox gage where the regressions were developed. Areas of 

forest types affected by the 

upstream salinity movements 
26 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

were calculated from the forest 

map for each flow reduction.

Wetland areas estimated to 

change in forest composition were 

calculated using both altered and 

unaltered areas. Most altered wetland forests were logged or planted 

in pines, and have the potential to 

return to natural forests.

In addition to forest composition changes, losses of inundated 

and saturated area in riverine forests were calculated for five hypothetical flow reductions in relation 

to the flow at which those reductions occur. The inundated or saturated area that would exist at each 

hypothetical reduced flow was subtracted from the inundated or saturated area existing at the original 

(unimpacted) flow for each flow 

increment up to a high flow of 

800 m3

/s (28,250 ft3/s). This loss of 

area, in hectares, was then divided 

by the original area, in hectares, to 

get the loss of area, in percent, for 

each flow reduction occurring at 

each flow increment.

Measurable and unmeasurable errors are inherent in calculations of data for impact analysis. 

Amount of error can be estimated 

for long-term surface-water flow and 

stage records, stage-discharge relations, water-level measurements at 

the transects, land-surface elevation 

surveys, latitude and longitude readings, soil and water conductivity 

measurements, and forest map accuracy. Amount of error cannot be 

estimated for the location of 

transects on GIS images, plant identifications, soil profile descriptions, 

and soil moisture observations. In 

addition, error cannot be quantified 

for the accuracy with which 1) landsurface elevations and soils at the 

transects represent the entire floodplain, 2) hydrologic conditions on 

the various field dates represent the 

typical conditions in the floodplain, 

and 3) selected critical flow statistics 

represent the determining factors of 

forest composition.

The large number of measurements and observations made 

in this study provided adequate replicate sampling for the various 

types of data, and increased the 

probability that the data collected 

are representative of the entire 

floodplain. As a result, error was 

greatly minimized in the final 

estimates of impacts from flow 

reductions. Error was further minimized because the estimates of 

impacts from flow reductions were 

based on relative change. The type 

and amount of error inherent in the 

new condition under each hypothetical flow reduction was the same 

error inherent in the existing condition that the new condition was 

compared against.

HYDROLOGIC CHARACTERISTICS OF THE RIVER

Long-term hydrologic characteristics of the river, including 

flow, stage, tidal range, storm 

surges, and salinity, have a major 

influence on the hydrology, soils, 

and vegetation of the floodplain.

Flow

Flows are usually highest in 

March and April, and lowest in 

November and December (fig. 13). 

Median daily flow was approximately 181 m3

/s (6,480 ft3/s), with 

typical annual flows ranging from 

the median annual 1-day low flow 

of 101 m3

/s (3,600 ft3/s) to the 

median annual 1-day high flow of 

571 m3

/s (20,400 ft3/s) based on 

Branford-Fort White flows from 

1933 to 1999 (table 8). The lowest 

daily mean flow in the period of 

record was 61.7 m3

/s (2,202 ft3/s) 

on December 19, 1990, and the 

highest flow was 2,425 m3

/s 

(86,610 ft3

/s) on April 11, 1948. 

The maximum 1-day flow in 1948 

had a recurrence interval of approximately 250 years. The maximum 

threshold 14-day flow in the 1948 

flood had a recurrence interval of 

about 75 years. Maximum 1-day 

flows occurring during the 3 years 

MEAN MONTHLY FLOW

MEDIAN MONTHLY FLOW

0

100

200

300

400

500

OND J FMAM J J A S

FLOW, IN CUBIC METERS PER SECOND

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

FLOW, IN CUBIC FEET PER SECOND

MONTHS

Figure 13. Mean and median monthly flows of the lower Suwannee River, 

Florida, 1933-99. Flow is combined flow of Suwannee River at Branford and Santa 

Fe River near Fort White.
Hydrologic Characteristics of the River 27

Table 8. Basic flow characteristics of the lower Suwannee River, Florida, 1933-99

[Flows are combined flows of Suwannee River at Branford and Santa Fe River near Fort White. Recurrence intervals for maximum 1-day flows and maximum threshold 14-day flows were calculated using 

log-Pearson Type III analysis. m3

/s, cubic meters per second; ft3/s, cubic feet per second; %, percent]

Flow descriptor

 Flow

m3

/s ft3/s

Lowest 1-day flow (December 19, 1990) 61.7 2,200

95% exceedance flow 83.8 2,990

90% exceedance flow 95.4 3,410

Median annual 1-day low flow1 101 3,600

75% exceedance flow 120 4,300

Median (50% exceedance) flow 181 6,480

Mean flow 243 8,670

25% exceedance flow 297 10,590

10% exceedance flow 473 16,900

Median annual 1-day high flow2 571 20,400

5% exceedance flow 608 21,710

Highest 1-day flow (April 11, 1948) 2,425 86,610

Recurrence

interval

Maximum 1-day flow3

2-year 568 20,290

5-year 885 31,590

10-year 1,120 39,990

25-year 1,445 51,600

50-year 1,707 60,960

100-year 1,985 70,900

200-year 2,282 81,510

500-year 2,706 96,640

Maximum threshold

14-day flow

2-year 491 17,550

5-year 749 26,750

10-year 921 32,910

25-year 1,138 40,650

50-year 1,298 46,350

100-year 1,455 51,970

200-year 1,611 57,550

500-year 1,817 64,880

1

 Median annual 1-day low flow is based on climatic years of April 1-March 31. 2

 Median annual 1-day high flow is based on water years of October 1-September 30. 3

 Includes August 1928 peak determined from flood mark.

of data collection in this study had 

approximate recurrence intervals of 

1.7 years for the 1997 flood 

(508 m3

/s, 18,150 ft3/s), 25 years for 

the 1998 flood (1,434 m3

/s, 

51,220 ft3

/s), and 2.5 years for the 

1999 flood (612 m3

/s, 21,870 ft3/s). 

Flow at the confluence of the 

Suwannee and Santa Fe Rivers is 

unaffected by tides. Flow varies 

with the tidal cycle during low-flow 

periods at the Wilcox gage (rkm 

53.8) and at all downstream 

locations, usually with highest 

flows on the falling tide and lowest 

flows on the rising tide. Near Manatee Springs (rkm 39.1), flow measurements made during very low 

flow (83.5 m3

/s, 2,950 ft3/s) were 

close to zero on the rising tide; flow 

reversals (negative flows) probably 

occur at that location under certain 

conditions (J. Grubbs, U.S. Geological Survey, oral commun., 2000). 

Flow reversals occur at Fowlers 

Bluff gage during low flow, and 

occur nearly every day at the 

Gopher River gage during low and 

medium flows.

Stage and Tidal Range

River stage at four gaging 

stations used in this study is shown 

in figure 14 for water years 1997, 

1998, and 1999. Daily stage fluctuations are non-tidal at the two 

most upstream gages, Branford and 

Bell. In this report, daily stage 

fluctuations less than 6 cm are considered to be non-tidal. Daily stage 

fluctuations at the Wilcox gage are 

tidal during low flow but not during 

floods. Daily tidal fluctuations at 

the Gopher River gage occurred at 

all flows including the peak of the 

25-year flood in 1998.

Tides are mixed semi-diurnal 

typically with two unequal high 

tides and two unequal low tides 

each day. The median tidal range at 

the mouth of the Suwannee River is 

about 1 m (Tillis, 2000). Typical 

tidal range at the Gopher River 

gage is approximately 0.85 m at 

both the median annual 1-day low 

flow and the median flow (fig. 9). 

Tidal range at this gage was about 

0.15 m during the peak of the 25-

year flood in 1998 (fig.14). Typical 

tidal range at the Wilcox gage is 

about 0.3 m at low flow, decreases 

to 0.15 m at median flow, and is 

non-tidal at high flow. Typical 

monthly and daily stages at tidal 

transects (MMH, MDH, and MDL) 

are described in appendix I.

Sea level rise has been estimated for Florida’s Gulf coast in 

the vicinity of the mouth of the 

Suwannee River at 30.5 cm since 

1852 (Raabe, 2000). Evidence that 

the Suwannee River estuary and 

nearby areas are experiencing sea 

level rise and coastal forest retreat 

has been presented by a number of 

investigators including Kurz and 

Wagner, 1957; Carlton, 1977; 

Clewell and others, 1999; and 

Williams and others, 1999.
28 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

-2

0

2

4

6

8

GOPHER RIVER (RKM 9.1)

WILCOX (RKM 53.8)

BELL (RKM 90.9)

BRANFORD (RKM 122.5) 1997

-2

0

2

4

6

8

10

12

BRANFORD (RKM 122.5)

BELL

(RKM 90.9)

WILCOX

(RKM 53.8)

GOPHER RIVER (RKM 9.1)

1998

ELEVATION, IN METERS ABOVE SEA LEVEL

1999

-2

0

2

4

6

8

BRANFORD (RKM 122.5)

BELL (RKM 90.9)

WILCOX (RKM 53.8)

GOPHER RIVER (RKM 9.1)

OCT NOV DEC JAN FEB MAR APR MAY JUNE JULY AUG SEPT

WATER YEAR

Hurricane Josephine

Hurricane Earl

Figure 14. River stage during the 1997, 1998, and 1999 water years at four gaging stations on the lower Suwannee 

River, Florida. Daily mean stages are shown for Branford and Bell, hourly stages for Wilcox, and 15 minute stages for 

Gopher River.
Topography and Hydrology of Forested Floodplain 29

Storm Surge

At the Gopher River gage, 

stages during storm surges are 

higher than river flood stages; however, the duration of storm surges is 

usually less than 24 hours. The highest storm surge in the 3-year study 

period occurred October 7-8, 1996, 

during Hurricane Josephine. Peak 

stages during this storm were 2.0 m 

above sea level at the Gopher River 

gage (fig. 14) and 2.2 m above sea 

level at the Upper West Pass gage.

A non-tropical winter storm 

known as the Superstorm of March 

1993 produced a storm surge of 

2.9 m at Cedar Key (National 

Oceanic and Atmospheric Administration, 1994). Slightly higher storm 

surges of 3.1 m were recorded at 

Cedar Key in June 1972 during Hurricane Agnes and in June 1966 during Hurricane Alma. Much higher 

storm surges are reported to have 

occurred in the 1800’s. A storm 

surge in 1882 was estimated to be 

4.9 m above sea level, and another in 

1842 reached approximately 5.5 m 

above sea level in Cedar Key (Ho 

and Tracey, 1975).

Salinity

Salinity in the lower tidal 

reach of the Suwannee River varies 

temporally and spatially in 

response to many factors.

Salinity is greater at high tide 

than at low tide. At the Upper West 

Pass gage (rkm 4.5), mid-depth 

salinities at high tide over the 

course of a week during low flow 

(Sept. 24-30, 1996) ranged from 3 

to 15 parts per thousand (ppt). All 

mid-depth salinities recorded at low 

tide during that same week were 

0 ppt (Tillis, 2000). All salinities 

described subsequently in this 

report were collected at high tide.

Salinity decreases upstream. 

While the salinity of seawater averages 33 ppt, salinities in Suwannee 

Sound range from 20 to 30 ppt during low flow (Orlando and others, 

1993). Under low-flow conditions, 

vertically averaged salinities are 

typically 20 ppt at the mouth of 

Wadley Pass, 10 ppt at rkm 2.9 in 

West Pass, 5 ppt at rkm 4.5 in West 

Pass, 2 ppt at the confluence of 

West and East Passes, and 0.5 ppt 

near the mouth of the Gopher River 

(Tillis, 2000).

Salinity is greater at the bottom of the river channel than at the 

surface. At the mouth of West 

Pass, mean bottom salinity (15 ppt) 

is higher than mean surface salinity 

(6.3 ppt) (Mattson and Krummrich, 

1995). Differences between surface 

and bottom salinities decrease 

upstream. At rkm 2.9 in West Pass, 

the mean bottom salinity (7.2 ppt) 

is higher than the mean surface 

salinity (4.7 ppt). Vertically averaged or mid-depth salinities are 

roughly comparable to the average 

of surface and bottom salinities.

Salinity increases as flow 

decreases. At rkm 2.9 in West 

Pass, vertically averaged salinities 

are typically less than 0.5 ppt during high flow, 5 ppt at medium 

flow, and greater than 10 ppt at low 

flow (Tillis, 2000).

Salinities are highest during 

storm surges that occur when river 

flows are low. The highest salinities 

measured over a 2-year period at a 

continuous recording (mid-depth) 

salinity station in West Pass (rkm 

4.5) were 30 ppt during Hurricane 

Opal on October 4, 1995 (Tillis, 

2000), and 23.6 ppt during Hurricane Josephine on October 8, 1996 

(G. Tillis, U.S. Geological Survey, 

oral commun., 2000). Both of these 

storms occurred during periods of 

low flow. The highest salinities 

recorded upstream of the confluence of West and East Passes were 

collected during an unnamed storm 

on October 30, 1993, that also 

occurred during low flow (Mattson 

and Krummrich, 1995). Bottom 

salinities were 13.9 ppt at the confluence of East and West Passes, 

11.0 ppt at the mouth of Gopher 

River, and 5 ppt at the mouth of 

Sandfly Creek (J. Krummrich, Florida Fish and Wildlife Conservation 

Commission, written commun., 

2000). Salinities at these locations 

are probably much higher during 

larger storms, because the middepth salinity at the upper West 

Pass gage during this unnamed 

storm (13.7 ppt) was much lower 

than that reported for Hurricanes 

Opal and Josephine (30 and 

23.6 ppt, respectively).

Hurricane season in the Gulf 

of Mexico is June 1-November 30 

with 84 percent of all hurricanes 

occurring during August and September (Organization of American 

States, 1991). Hurricane season 

occurs primarily when flows are 

below the median flow of 181 m3

/s 

(6,480 ft3

/s) (fig. 13).

TOPOGRAPHY AND 

HYDROLOGY OF 

FORESTED FLOODPLAIN

Topographic and hydrologic 

features of the floodplain are 

important factors affecting soil 

characteristics and forest composition and distribution.

Land-Surface Elevations, 

Hydrologic Conditions, and 

Forest Types at Transects

Elevation and topographic 

relief in the floodplain decreases 

with proximity to the Gulf (fig. 15). 
30 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

50%

TRANSECT ELEVATION

ESTIMATED ELEVATION

DISTANCE--In river kilometers

PERCENT OF TIME STAGE IS

EQUALED OR EXCEEDED

FOREST TYPE LOCATION--Yellow for riverine, green for upper tidal, and blue for lower tidal

RKM 77.7

MEDIAN MONTHLY HIGH STAGE

MEDIAN DAILY HIGH STAGE

MEDIAN DAILY LOW STAGE

V1-5 VERIFICATION PLOT

MMH

MDH

MDL

EXPLANATION

Rblh1

2-year, 1-day high

5-year, 1-day high

2-year, 1-day high

1

2

3

4

5

6

3

4

5

6

7

8

0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200 1,300

0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200 1,300

DISTANCE FROM BEGINNING OF TRANSECT, IN METERS

ELEVATION, IN METERS ABOVE SEA LEVEL

CF transect (RKM 104.4)

25%

50%

10%

Suwannee River

5-year, 1-day high

Rblh3

Rblh2

Rblh1

Rsw2

Rsw1

Oak/Pine

Rblh1

Rsw2

Rsw1

25%

50%

10%

Suwannee River

Rblh3

Rblh2

Rblh1

Rsw2

Rsw1

Rblh3

Rblh2

Rblh1

Rsw2

Rsw1

LL transect (RKM 77.7)

V1-5

Figure 15. Land-surface elevations and forest types at floodplain transects in relation to long-term 

hydrologic conditions in the lower Suwannee River, Florida. Stages for the 2-year and 5-year, 1-day highs 

and percent exceedance are derived from daily mean values (1933-99). MMH, MDH, and MDL stages are 

calculated from unit values (1986-99). The 1948 and 1998 floods, with recurrence intervals of approximately 

250 and 25 years, respectively, are shown at most lower tidal transects where 2-year and 5-year floods are 

less important. Hurricane Josephine occurred on October 7-8, 1996. Hydrology is not shown at BC, which is 

too far from the river to estimate transect water levels from river stage.
Topography and Hydrology of Forested Floodplain 31

DISTANCE FROM BEGINNING OF TRANSECT, IN METERS

ELEVATION, IN METERS ABOVE SEA LEVEL

0 100 200 300 400 500 600 700 800 900 1,000 1,100 1,200 1,300

0 100 200 300 400 500 600 700 800 900 0 100 200

MS transect (RKM 42.5)

10%

25%

50%

MMH

MDH

MDL

FK transect (RKM 64.5)

25%

50%

10%

MMH

MDH

MDL

0 100 200 300 400 500 600 700 800 900 1,000 1,100

5-year, 1-day high

2-year, 1-day high

5-year, 1-day high

2-year, 1-day high

2-year, 1-day high and Hurricane Josephine

5-year, 1-day high

0

1

2

3

4

5

-1

0

1

2

3

0

1

2

3

4

UTblh UTmix UTmix UTsw2

UTsw1

Marsh

Rblh3

Rblh2

Rblh1

UTsw2

UTsw1

Rblh3

Rblh2

Rblh1

UTsw2

UTsw1

Rblh2

Rblh1

Rsw2

Rblh1

Rsw1

Suwannee River

Suwannee River

Perpendicular transect

KI starts here KN transect (RKM 31.2) KI transect

Suwannee River

Figure 15. Land-surface elevations and forest types at floodplain transects in relation to long-term 

hydrologic conditions in the lower Suwannee River, Florida. Stages for the 2-year and 5-year, 1-day highs 

and percent exceedance are derived from daily mean values (1933-99). MMH, MDH, and MDL stages are 

calculated from unit values (1986-99). The 1948 and 1998 floods, with recurrence intervals of approximately 

250 and 25 years, respectively, are shown at most lower tidal transects where 2-year and 5-year floods are 

less important. Hurricane Josephine occurred on October 7-8, 1996. Hydrology is not shown at BC, which is 

too far from the river to estimate transect water levels from river stage. (Continued)
32 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

SN transect SH transect

(Near RKM 12.9)

LTsw2

LTsw1

0 100 200

Suwannee River

(RKM 4.8)

0 100 200 300

1998 flood

LTham

ELEVATION, IN METERS ABOVE SEA LEVEL

Suwannee

River

0

1

2

3

-1

0 100 200 300 400 500 600 700

TK transect (RKM 19.9)

Hurricane Josephine

2-year, 1-day high 5 -year, 1-day high

1948 flood 1998 flood

MMH

MDH

LTsw2

LTsw1

MDL

0 100 200

0

1

2

3

-1

MMH

MDH

MDL

LTmix

1948 flood

BC transect

(Near RKM 11.2)

LTmix

LTsw2

LTsw1

LTmix

LTsw1

0 100 200 300 0 100 200

0

1

2

3

-1

-2

0

1

2

3

-1

-2

Suwannee River

MMH

MDH

MDL

(RKM 5.2)

1998 flood

DISTANCE FROM BEGINNING OF TRANSECT, IN METERS

Hurricane Josephine

Hurricane Josephine

1948 flood

MMH

MDH

MDL

LTsw2

TRANSECT ELEVATION

ESTIMATED ELEVATION

DISTANCE--In river kilometers

MEDIAN MONTHLY HIGH STAGE

MEDIAN DAILY HIGH STAGE

MEDIAN DAILY LOW STAGE

FOREST TYPE LOCATION--Yellow

for riverine, green for upper tidal,

and blue for lower tidal

RKM 12.9

EXPLANATION

LK

transect

DM

transect

Figure 15. Land-surface elevations and forest types at floodplain transects in relation to long-term 

hydrologic conditions in the lower Suwannee River, Florida. Stages for the 2-year and 5-year, 1-day 

highs and percent exceedance are derived from daily mean values (1933-99). MMH, MDH, and MDL 

stages are calculated from unit values (1986-99). The 1948 and 1998 floods, with recurrence 

intervals of approximately 250 and 25 years, respectively, are shown at most lower tidal transects 

where 2-year and 5-year floods are less important. Hurricane Josephine occurred on October 7-8, 

1996. Hydrology is not shown at BC, which is too far from the river to estimate transect water levels 

from river stage. (Continued)
Topography and Hydrology of Forested Floodplain 33

The highest elevation and greatest 

relief are at the most upstream 

transect (CF), where elevations 

range from 4.1 to 7.3 m above sea 

level. The greatest range in river 

stage also is at the most upstream 

transect, with a typical annual range 

of 4.1 m. The lowest elevations and 

least relief are at the lower tidal 

transects (TK, SN, SH, BC, LK, 

and DM), where elevations range 

from 0.3 to 1.3 m above sea level. 

Throughout the remainder of this 

report, specific locations on 

transects are identified with the 

transect name and a number corresponding to the distance from the 

beginning of the transect shown on 

the horizontal axes in figure 15. For 

example, TK-290 identifies the 

location of the deepest tidal creek 

on the TK transect.

Elevations associated with a 

variety of statistics describing longterm hydrologic conditions in the 

river channel are shown with each 

cross section in figure 15. The horizontal bars shown above the cross 

sections indicate the extent of 

mapped forest types at each 

transect. Median elevations of each 

forest type at each transect are presented in appendix II. 

In figure 15, lines indicating 

flood elevations (and Hurricane 

Josephine storm surge at most tidal 

transects) are shown extending 

across the entire cross section for 

each transect, because river stages 

during these episodic flood or 

storm events are high enough to 

inundate most or all of the transect 

land surface. Conversely, lines 

indicating elevations for percent 

exceedance at riverine transects, 

and MMH, MDH, and MDL at tidal 

transects are not shown extending 

acros the cross sections; when river 

levels are below flood stage, water 

levels in the floodplain are related 

to, but are not necessarily the same 

as, river levels in the main channel. Intervening levees and ridges 

can delay or prevent water from 

entering or exiting depressions. In 

some riverine swamps, water levels 

may be higher than river stage 

because of local rainfall, residual 

floodwaters, or ground-water seepage from adjacent uplands. In tidal 

forests, high tides last only an hour 

or two and may not reach partially 

isolated swamps near the upland 

edge and relatively far from the 

main channel. Actual hydrologic 

conditions along floodplain 

transects were observed during a 

variety of flow conditions during 

the 3-year data collection period 

(app. III). 

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. On three of 

the four riverine transects, there is a 

second higher ridge directly behind 

the riverbank levee. Most levees 

and high ridges are vegetated with 

high bottomland hardwood forests 

(Rblh2 and Rblh3). 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 downstream of MS. The 

highest elevations on tidal transects 

are found in the UTblh forest on the 

KI transect, in the LTham forest on 

the SH transect, and on the tops of 

the higher hummocks on the TK, 

SN, BC, and LK transects. These 

higher elevations are above the 

MMH, but are submerged by large 

floods and storm surges. 

Depressions on riverine 

transects are vegetated with 

swamps (Rsw1 and Rsw2). Water 

levels in riverine swamps are sometimes higher than water levels in the 

river channel, particularly at the CF 

transect, where pond levels are 1-2 

m above river levels during low and 

medium flows. Duration of inundation in riverine forests varies with 

river flow. Standing water disappears in all riverine swamps during 

severe droughts. 

More than two-thirds of the 

MS transect is covered by upper 

tidal swamps that are isolated from 

regular tidal inundation by high 

riverbank levees. The shallow puddles of water or soupy mud commonly found throughout most of 

these swamps do not fluctuate with 

the tides (fig. 7). The water table is 

probably near land surface year 

round in MS swamps because most 

land-surface elevations in these 

swamps are close to the elevation of 

the MDH. 

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 

(fig. 16). River flooding dominates 

the hydrograph about one-third of 

the time at the MS transect, about 

one-tenth of the time at TK 

transect, and rarely at the LK and 

DM transects. Median elevations 

of forest types are more deeply 

inundated by daily and monthly 

tidal fluctuations with proximity to 

the Gulf. Elevations of storm surges 

are much lower than the 2-year, 

1-day high at MS, are similar to 

major flood stages at TK, and are 

much higher than any river flooding 

at LK and DM. 

Tidal creeks flowing in and 

out with daily tides were observed 

at KN-240, TK-290 (fig. 17), and 

SN-30. Swamps at KN and TK are 

below the MMH and the riverward 

half of those transects receive direct 

tidal inundation from tidal creeks. 
34 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

KN and KI (RKM 31.2)

UTsw1/sw2

UTsw1/sw2

Rblh2

Rblh1

Rblh3

Hurricane

Josephine

3-year

flood

5-year

flood

10-year

flood

3-year

flood Hurricane

Josephine

25-year

flood

2-year

flood

25-year

flood

2-year

flood

-0.5

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

1985 86 87 88 89 90 91 92 93 94 95 96 97 98 1999

UTmix

UTblh

2.0

2.5

3.5

4.5

0

0.5

1.0

1.5

3.0

4.0 MS (RKM 42.5)

5-year

flood

10-year

flood

CALENDAR YEAR

ELEVATION, IN METERS ABOVE SEA LEVEL

EXPLANATION

ESTIMATED DAILY HIGH STAGE--At transects

MEDIAN ELEVATION OF FOREST TYPE--With unrestricted inundation from river

MEDIAN ELEVATION OF FOREST TYPE--With river inundation partially restricted

by intervening higher elevations

Figure 16. Forest type elevations in relation to daily high river stage from 1985 to 1999 at transect locations in the upper 

and lower tidal reaches of the Suwannee River, Florida. At all transects except LK and DM, daily high stage was estimated 

by interpolation between gages. Daily high stage at LK and DM transects was extrapolated from long term Gopher River 

gage data, based on a comparison of 3 years of concurrent data at both the Upper West Pass and Gopher River gages. BC 

transect is not included because it is located too far from the main channel to relate transect elevations to river stage.
Topography and Hydrology of Forested Floodplain 35

5-year flood

TK (RKM 19.9)

LTsw1/sw2

Hurricane

Josephine

3-year

flood

Hurricane

Earl

LTham

LTmix

Hurricane

Earl

Hurricane

Josephine

5-year

flood

SN and SH (RKM 12.9)

LK (RKM 5.2) and DM (RKM 4.8)

LTmix

Hummock top

Hurricane Juan

Hurricane Elena

LTsw1/sw2

5-year

flood

Hurricane

Josephine Hurricane

Earl

3-year

flood

1985 86 87 88 89 90 91 92 93 94 95 96 97 98 1999

-0.5

0

0.5

1.0

1.5

2.0

2.5

3.0

CALENDAR YEAR

ELEVATION, IN METERS ABOVE SEA LEVEL

-0.5

0

0.5

1.0

1.5

2.0

2.5

10-year

flood

25-year

flood

-0.5

0

0.5

1.0

1.5

2.0

2.5

25-year

flood

10-year

flood

Unnamed

storm

October,

1992

Unnamed

storm

October,

1994

25-year

flood

2-year

flood

Unnamed

storm

October,

1992

10-year

flood

2-year

flood

EXPLANATION

ESTIMATED DAILY HIGH STAGE--At transects

MEDIAN ELEVATION OF FOREST TYPE--With unrestricted inundation from river

MEDIAN ELEVATION OF FOREST TYPE--With river inundation partially restricted

by intervening higher elevations

Figure 16. Forest type elevations in relation to daily high river stage from 1985 to 1999 at transect locations in the upper and 

lower tidal reaches of the Suwannee River, Florida. At all transects except LK and DM, daily high stage was estimated by 

interpolation between gages. Daily high stage at LK and DM transects was extrapolated from long term Gopher River gage 

data, based on a comparison of 3 years of concurrent data at both the Upper West Pass and Gopher River gages. BC 

transect is not included because it is located too far from the main channel to relate transect elevations to river stage. 

(Continued)
36 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

The back half of these swamps 

(near the uplands) are semi-isolated 

from regular tidal inundation. 

Water levels measured in shallow 

pools in semi-isolated swamps from 

KN-450 to 700 and TK-0 to 160 did 

not fluctuate with the tides except 

when river levels were above the 

MMH. All of the LTmix forest at 

SN receives direct tidal inundation 

from the tidal creek on that transect. 

Swamps and mixed forests at LK 

and DM are intertidal because they 

are below the MDH and receive 

Figure 17. Tidal creek at low tide in LTsw2 forest on TK 

transect in the lower Suwannee River floodplain, Florida. 

At high tide, water fills the creek and flows out onto the 

adjacent forest. High tide usually does not last long enough 

for water to work its way across the entire forest floor, even 

though land-surface elevations of distant swamps may be 

similar to those of swamps adjacent to the creek.

Figure 18. Shore of the Suwannee River, Florida, near DM 

transect at very low tide. The intertidal zone lies between the 

median daily high and low stages. Daily high tide covers not 

only this muddy shore, but floods the forest floor as well.

direct tidal inundation from the 

river channel (fig. 18). 

Hummocks at the bases of 

trees are present at nearly all 

transects, but are more common at 

lower tidal transects where they are 

usually large and well defined 

(fig. 19). 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. Although the distinction between these two forest types 

is evident on the ground, small 

areas containing hammock species 

that were visible on aerial photography were not separately mapped 

for this study unless the hammock 

areas exceeded the minimum mapping unit size of 500 m2

. Forests 

with few hummocks at TK are 

mapped as LTsw1 and LTsw2, and 

forests with numerous small hummocks at SN or few large hummocks at LK are mapped as LTmix.
Topography and Hydrology of Forested Floodplain 37

Salinity in Floodplain Water 

Bodies of Lower Tidal 

Reach

Salinities in tidal creeks at 

KN-240, TK-290, and SN-30 are 

probably similar to the main river 

channel because they are connected 

to the river by daily tidal flow. 

The river is fresh at KN and TK 

transects under normal conditions; 

salinities during storm surges are 

unknown at those locations. The 

river is usually fresh (less than 

0.5 ppt) at the mouth of Sandfly 

Creek (rkm 12.9) except during 

storm surges. Maximum salinity 

measured near the mouth of 

Sandfly Creek was 5 ppt at the bottom (and probably exceeded 0.5 ppt 

at the surface) during a minor storm 

surge on October 30, 1993 

(J. Krummrich, Florida Fish and 

Wildlife Conservation Commission, written commun., 2000). 

Surface salinities near the mouth of 

Sandfly Creek and in the tidal creek 

Figure 19. A well-defined hummock that is large enough to support several trees 

on BC transect in the lower Suwannee River floodplain, Florida. Hammock tree 

species can grow within a swamp forest on the elevated soil of hummocks, but 

cannot survive on the surrounding mud floor.

at SN-30 are probably much higher 

during large hurricanes that make 

landfall during low-flow periods.

Salinity of surface waters in 

isolated ponds of lower tidal forests 

is sometimes higher than salinity in 

the main river channel (fig. 20). 

Water salinities can be elevated in 

isolated ponds because saline water 

is periodically deposited by storm 

surges. The isolated position of 

these ponds in the landscape prevents them from being flushed by 

fresh or less saline water from the 

river and tidal creeks. During 

droughts, pond salinities increase as 

ponds shrink from evaporation. 

Salts build up in the soils, so that 

even after being flushed with fresh 

water during major river flooding, 

the ponds return gradually to their 

saline conditions after the flood 

recedes.

The highest water salinity 

measured in the floodplain in this 

study (5.2 ppt) occurred in an isolated pond at BC transect (fig. 21) 

in February 1997, about 4 months 

after Hurricane Josephine (fig. 20). 

The storm surge from Hurricane 

Josephine probably deposited 

saline water on both the BC and SH 

transects. The lowest salinity measured at lower tidal study sites 

(0.05 ppt) also occurred at the BC 

transect (and was assumed to be 

similar at SH and TK) during a 25-

year flood in March 1998, when the 

entire floodplain was covered with 

fresh river water moving downstream as sheet flow through the 

forest. Less than 2 months after the 

flooding receded, salinity began 

increasing at both BC and SH 

transects, probably due to salts 

moving out of the soil as the ponds 

shrunk from evaporation (Hanlon 

and others, 1993). Storm surges 

from Hurricanes Earl and Georges 

in September 1998, although 

smaller than Hurricane Josephine, 

may have brought more saline 

water to the ponds. The ponds 

shrunk in size and salinities generally increased in 1999 as a result of 

the drought conditions in the summer and fall of that year.

Salinity of isolated ponds 

increases with proximity to the 

coast. Isolated ponds in the 

upstream portion of the lower tidal 

reach at TK transect always seem to 

contain freshwater (less than 

0.5 ppt salinity) (fig. 20). Isolated 

ponds are usually oligohaline (0.5 

to 5.0 ppt) in the lower half of the 

lower tidal reach at SH and BC 

transects, and rarely mesohaline 

(greater than 5 ppt) at BC transect. 

In straight-line distances, TK, SH, 

and BC transects are approximately 

12, 7, and 5 km from the Gulf, 

respectively. Water samples collected at several other sites in lower 

tidal forests (app. IV) generally 

confirm the downstream salinity 

gradient depicted in figure 20.
38 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

0

1

2

3

4

5

6

CALENDAR YEAR

ISOLATED POND ON BC TRANSECT

ISOLATED POND NEAR SH TRANSECT

SEMI-ISOLATED POND ON TK TRANSECT

1996 1998 1999 1997

Hurricane

Josephine

25-Year

Flood Hurricane Earl

Hurricane Georges

SALINITY, IN PARTS PER THOUSAND

Figure 21. Isolated pond at BC transect 

in the winter in the lower Suwannee River 

floodplain, Florida. The highest water 

salinity measured in the floodplain in this 

study (5.2 parts per thousand) occurred 

here about 4 months after a storm surge 

from Hurricane Josephine.

Figure 20. Salinity of surface-water samples 

collected at selected sites in lower tidal forests 

in the floodplain of the lower Suwannee River, 

Florida. Salinity was calculated from electrical 

conductivity (EC) using the formula: Salinity, 

in parts per thousand = EC, in millimhos per 

centimeter x 0.65 (adapted from Hem, 1985). 

Salinity near zero on 3-25-98 was estimated 

for all sites from salinity measured at BC 

transect. During this 25-year flood event, the 

entire floodplain was covered with fresh river 

water moving downstream through the forest 

as sheet flow.
Soil Characteristics 39

SOIL CHARACTERISTICS

Soils are an important ecological component of floodplain 

forests. Hydrologic conditions 

influence the characteristics of 

floodplain soils, and both hydrology and soils affect vegetative communities. In an earlier report by 

Howell (1999), soil characteristics 

at most of the transects in this study 

were described and compared. 

Howell’s (1999) report included 

discussions of soil taxonomy,

Table 9. Taxonomic classification of soils in floodplain forests of the lower Suwannee River, Florida

A. Oak/pine uplands and riverine wetlands B. Upper and lower tidal wetlands

Forest 

type Profile name Order Taxon subgroup Forest type Profile name Order Taxon subgroup

Oak/pine CF-1066 Ultisols Grossarenic Paleudults UTblh KI-56 Entisols Typic Psammaquents

Rblh3

CF-144 Ultisols Grossarenic Paleudults UTmix KN-0 Mollisols Typic Argiaquolls

LL-707 Entisols Aquic Quartzipsamments KN-729 Inceptisols Typic Humaquepts

LL-732 Entisols Aquic Quartzipsamments UTsw2 MS-623 Entisols Fluvaquents

MS-173 Spodosols Ultic Alaquods KN-50 Mollisols Histic Endoaquolls

Rblh2

CF-10 Ultisols Aquic Arenic Paleudults

UTsw1

MS-250 Mollisols Histic Endoaquolls

CF-25 Mollisols Typic Argiaquolls KN-122 Histosols Terric Haplosaprists

CF-94 Entisols Aquic Quartzipsamments KN-199 Histosols Fluvaquentic Haplosaprists

LL-548 Entisols Fluvaquents KN-632 Entisols Fluvaquents

LL-783 Ultisols Arenic Hapludults

LTham

SH-0 Inceptisols Typic Humaquepts

FK-9 Entisols Aquic Quartzipsamments SH-40 Spodosols Typic Alaquods

MS-887 Entisols Typic Psammaquents SH-65 Inceptisols Typic Humaquepts

Rblh1

CF-169 Ultisols Grossarenic Paleudults OS4-67 Alfisols Arenic Endoaqualfs 

CF-303 Entisols Typic Psammaquents

LTmix

SN-17 Histosols Terric Haplosaprists

LL-0 Entisols Fluvaquents SN-34 Inceptisols Typic Humaquepts

LL-917 Entisols Fluvaquents SN-77 Histosols Terric Haplosaprists

FK-40 Alfisols Aeric Endoaqualfs BC-139 Histosols Terric Haplosaprists

FK-957 Inceptisols Typic Humaquepts LK-0 Histosols Typic Haplosaprists

MS-42 Inceptisols Typic Humaquepts

LTsw2

TK-30 Histosols Terric Haplosaprists

MS-939 Entisols Fluvaquents TK-206 Histosols Typic Haplosaprists

MS-1005 Entisols Fluvaquents TK-292 Histosols Typic Haplosaprists

Rsw2

CF-47 Mollisols Typic Argiaquolls BC-206 Histosols Terric Haplosaprists

CF-1108 Mollisols Typic Argiaquolls DM-7 Histosols Typic Haplosaprists

CF-1191 Ultisols Aquic Arenic Paleudults

LTsw1

TK-117 Histosols Typic Haplosaprists

LL-192 Entisols Fluvaquents TK-412 Entisols Fluvaquents

LL-400 Entisols Fluvaquents V4-10 Histosols Lithic Haplosaprists

LL-588 Entisols Fluvaquents BC-31 Histosols Terric Haplosaprists

FK-107 Mollisols Typic Argiaquolls LK-131 Histosols Typic Haplosaprists

FK-166 Mollisols Typic Argiaquolls

FK-210 Histosols Terric Haplosaprists

Rsw1

CF-211 Entisols Fluvaquents

CF-261 Entisols Fluvaquents

CF-286 Entisols Typic Psammaquents

CF-1143 Ultisols Arenic Paleaquults

CF-1153 Mollisols Typic Argiaquolls

FK-795 Histosols Typic Haplosaprists

FK-888 Histosols Terric Haplosaprists

FK-909 Histosols Terric Haplosaprists

FK-937 Inceptisols Typic Humaquepts

series, drainage class, horizons, texture, color, structure, mottles, and 

pH at each transect, and related 

these characteristics to topographic 

features without regard to forest 

type. Soil characteristics are related 

to forest types in this report. 

Taxonomic Classification

Taxonomic classifications of 

soils found in forest types of the 

lower Suwannee River floodplain 

are presented for 67 soil profiles in 

table 9. The 67 profiles were 

selected as a representative subset 

of a total of 96 soil profiles that 

were described in this study 

(app. V).

Soils in the forested floodplain are highly variable, with 

7 orders and 18 taxonomic subgroups (table 9). The most common floodplain soils are Entisols 

and Histosols. Entisols, which are 

recent soils that lack substantial 

profile development, are most common in the riverine reach and are 

important in every wetland forest 
40 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

type in that reach. Histosols, 

which are organic soils that have 

developed in water-saturated environments, dominate the swamps 

and mixed forests of the lower tidal 

reach, but are not present in the 

hammocks. Upstream of the lower 

tidal reach, Histosols are restricted 

to the wettest swamps (UTsw1 and 

Rsw1).

All seven soil orders listed in 

table 9 are found in both riverine 

and tidal forests with the exception 

of Ultisols, which occur only in 

riverine forests, primarily at the 

most upstream transect (CF). Ultisols are older, more weathered soils 

having argillic or kandic horizons 

with low base saturation.

Texture and Saturation

Soil textures associated with 

forest types are illustrated in 

figure 22 for the same 67 profiles 

that are listed in table 9. Surface 

soils are those soils found within 

the root zone (upper 30 cm), and 

subsurface soils are found below 

the root zone. The estimated percentage of each forest type at each 

transect that had continuously saturated soils in the upper 6 cm of the 

land surface during the 1996-99 

data collection period is provided 

in table 10.

Soils in all riverine forests, 

except Rsw1, are predominantly 

mineral (sand, loam, or clay) and 

are typically dry during low-flow 

periods. Soils in Rsw1, upper tidal, 

and lower tidal forests are predominantly organic on the surface, with 

organic or mineral subsurface textures. Most surface soils in Rsw1 

forests, upper and lower tidal 

swamps, and lower tidal mixed forests were continuously saturated 

during the data collection period.

Soils in the highest and driest 

forest types of all three reaches 

(oak/pine, Rblh3, Rblh2, UTblh, 

and LTham) generally have more 

sand throughout their profiles than 

other forest types of the same reach 

(fig. 22). High bottomland hardwoods in riverine and upper tidal 

reaches are typically found on 

levees and ridges (fig. 15). These 

sandy soils dry quickly after floods 

recede because of their low waterretention properties and their relatively high positions in the landscape. LTham forests are sandier 

than other lower tidal forest types, 

but commonly have a thin layer of 

muck on the surface. Hammocks 

are only slightly elevated (by about 

0.3 m) above mixed forests and 

swamps in the lower tidal reach, and 

thin surface mucks are probably 

maintained by a high water table. 

About 35 percent of the hammock 

transect at SH was continuously saturated during the 3-year data collection period (table 10). 

Surface soils of Rblh1 forests have a variety of textures 

including sand, mucky sand, loam, 

mucky loam, and clay, most of 

which are dry during low-flow 

periods. Soils of UTmix forests 

also have a variety of textures, 

sometimes with a thin layer of 

muck on the surface. Continuously 

saturated surface soils are more 

common in UTmix forests than in 

Rblh1 forests. Except for the sandy 

bed of a tidal creek at SN-34, surface soils of LTmix forests were 

saturated mucks; however, sandy 

subsoils in most LTmix forests 

probably provide slightly better 

drainage than in LTsw1 and LTsw2 

forests. The 200-cm thick section 

of muck at LK-0 is representative 

of all profiles at LK. Most of the 

LK transect is mapped as LTmix 

due to several large hummocks that 

support hammock species.

Surface soils in Rsw2 forests 

are primarily clay. These soils 

remain saturated most of the time 

under normal conditions, but are 

almost completely dry during 

extended periods of low flow. Surface soils in Rsw1 forests at CF 

transect are a mixture of sand, 

loam, clay, and muck; about onehalf of these soils remained saturated throughout the 1996-99 datacollection period (table 10). Surface soils in Rsw1 at the FK 

transect are mucks, most of which 

were continuously saturated during the data collection period. Saturated mucks at FK-795 to 937 are 

adjacent to an intermittent slough 

(at FK-774) that may be fed by 

flow from a small floodplain spring 

2 km north of the transect (J. Falkenburry, oral commun., 1997). Saturated muck at the land surface was 

observed in Rsw1 forests at LL1060; however, soil profiles were 

not described at this location and 

are not shown in figure 22. Continuously saturated mucks at LL-1060 

may be maintained by a small 

spring run flowing through the 

swamp.

Most surface soils in tidal 

swamps are saturated mucks except 

for UTsw2 forests at MS transect 

(fig. 22). Some high spots in the 

landscape, such as narrow riverbank levees (TK-412) and hummock tops, have better drained 

soils that are not continuously saturated, but these soils comprise only 

a small percentage of the floodplain area. The mud floors in all 

tidal swamps, including isolated 

swamps that do not receive regular 

tidal inundation, are maintained in 

a saturated condition because landsurface elevations of the mud floors 

are close to the elevation of the 

MDH. The mud floor at LK and 

DM transects is inundated by high 

tide almost daily.
Soil Characteristics 41

0

30

60

90

120

150

180

210

DEPTH BELOW LAND SURFACE, IN CENTIMETERS

0

30

60

90

120

150

180

210

0

30

60

90

120

150

180

210

0

30

60

90

120

150

180

210

0

30

60

90

120

150

180

210

CF10CF25CF94

LL548

LL783

FK9

MS887

CF169CF303

LL0LL917FK40FK957

MS42MS939MS1005

CF47CF1108CF1191

LL192LL400LL588FK107FK166FK210

CF211

CF261CF286

CF1143CF1153

FK795FK888FK909

FK937

CF1066CF144

LL707

LL732

MS173

MS250KN122

KN199

KN632

MS623

KN50

KI56

KN0KN729

SH0SH40SH65

OS4-

67

TK117TK412

V4-

10

BC31

LK131

SN17

SN34

SN77

BC139

LK0

TK30

TK206TK292

BC206DM7

DECREASING ELEVATION AND INCREASING WETNESS

DECREASING DISTANCE FROM RIVER MOUTH

Rblh2

Rblh1

Rsw2

Rsw1

Oak/Pine Rblh3

UTblh

UTmix

UTsw2

UTsw1

LTham

LTmix

LTsw2

LTsw1

RIVERINE UPPER TIDAL

LIMEROCK

AT

79 CM

LOWER TIDAL

Sand

Loam

Clay

Muck

Mucky sand

Mucky loam

Mucky clay

Mucky peat

PROFILE NAME--Numbers indicate distance from beginning of transect,

except for OS4-67 and V4-10 which are observation and verification sites.

APPROXIMATE

LOWER LIMIT

OF ROOT ZONE

RIVERBANK LEVEE

TIDAL CREEK BED

RBL

TCB

EXPLANATION

CF144

RBL

RBL

RBL

RBL

TCB

RBL

RBL

TCB

RBL

SOIL TYPE

Figure 22. Texture of soils in floodplain forests of the lower Suwannee River, Florida. See figures 2 and 15 for 

sampling location.
42 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Table 10. Continuously saturated soils in wetland forest types of the lower Suwannee River floodplain, 

Florida, 1996-99

[Estimated percentages of transect length with continuously saturated soils were based on observations of soil moisture in the upper 6 cm of the land 

surface during a variety of flow conditions from 1996 to 1999 (app. III). rkm, river kilometers; ---, forest type not present on transect]

Estimated amount of forest type at each transect with continuously saturated surface soils

during 3-year data collection period, in percent

(rkm of transect in parentheses)

CF

(104.4)

LL

(77.7)

FK

(64.5)

MS

(42.5)

KN/KI

(31.2)

TK

(19.9)

SN/SH

(12.9)

BC

(11.2)

LK/DM

(5.0)

High bottomland hardwoods

and hammocks

(Rblh3, Rblh2, UTblh, LTham)

0 0 0 0 0 --- 35 --- ---

Low bottomland hardwoods

and mixed forests 

(Rblh1, UTmix, LTmix)

0 0 0 15 37 --- 100 94 92

Swamp type 2

(Rsw2, UTsw2, LTsw2) 0 4 0 62 100 100 --- 94 100

Swamp type 1

(Rsw1, UTsw1, LTsw1) 54 100 82 95 99 99 --- 92 100

The only limerock observed 

in any of the 96 soil profiles 

throughout the floodplain was 

found at a depth of 79 cm in LTsw1 

forest at V4-10. Some evidence of 

limestone in the shallow subsurface 

was expected since the entire drainage basin of the lower Suwannee 

River is underlain by limestone, 

most of which is at or near land surface (Crane, 1986).

Conductivity in Lower Tidal 

Reach

Thirty-two soil samples from 

21 locations in floodplain forests of 

the lower tidal reach were analyzed 

for electrical conductivity (table 11). 

Results are graphically depicted in 

figure 23 using conductivity ranges 

modified from those in standard use 

for assessing salinity effects on 

agricultural crops (Richards, ed., 

1954). Soil conductivity has 

negligible effects on crops from 

0 to 2 millimhos per centimeter 

(mmhos/cm), reduces the yield of 

some crops from 2 to 4 mmhos/cm, 

reduces the yield of many crops 

from 4 to 8 mmhos/cm, and reduces 

the yield of all except the most salttolerant crops when greater than 

8 mmhos/cm (Richards, ed., 1954). 

Soil conductivity is generally 

accepted as a measurement of soil 

salinity, with a few exceptions that 

do not apply to soils described in 

this report (Richards, ed., 1954; 

Hanlon and others, 1993; USDA, 

1996). Soils are considered to be 

saline if the conductivity is greater 

than 4 mmhos/cm and the 

exchangeable sodium percentage is 

less than 15 (Richards, ed., 1954); 

however, soils were not classified 

as saline or non-saline in this report 

because exchangeable sodium percentage was not available for all 

samples.

Conductivity of surface soils 

in the upper part of the lower tidal 

reach has negligible effects on most 

tree species. Five surface soil samples collected in the vicinity of rkm 

20 had an average conductivity of 

0.9 mmhos/cm with a maximum 

conductivity of 1.9 mmhos/cm 

(table 11). In the downstream part 

of the lower tidal reach, however, 

conductivities of surface soils were 

high enough (greater than 4 

mmhos/cm) to exclude many nontolerant tree species at 6 of 11 locations from rkm 12.6 to the tree line. 

The highest soil conductivity measured in this study was 13.7 

mmhos/cm in surface soils of an 

isolated forest located at BC-139.

Surface soil conductivities in 

forests are comparable to those 

reported for marshes of the lower 

Suwannee River (Clewell and others, 1999). The average conductivity of surface soil samples in 

marshes at or upstream of the tree 

line was 3.3 mmhos/cm in August 

and November 1997, whereas the 

average conductivity of surface 

soils in marshes downstream of the 

tree line was 5.9 mmhos/cm on the 

same dates. Conductivity of marsh 

soils on two other sampling dates 

(February and June 1998) were not 

comparable to the present study 

because soil samples were collected 

during or soon after major flooding 

in 1998, which decreased soil conductivities at all sites.

Surface soils in some 

isolated forests have considerably 

higher conductivities than soils in 

forests that receive regular tidal 

inundation. Surface soil conductivities in isolated forests at BC (5.2-

13.7 mmhos/cm) were higher than 

in those in LK and DM forests that 

receive regular tidal inundation 

(1.5-4.6 mmhos/cm) (table 11). In 

a similar comparison of transects 

farther upstream, surface soil conductivity near the isolated pond at 

SH-0 (4.5 mmhos/cm) was higher 

than that in the mixed forest at 

SN-77 (1.4 mmhos/cm), which 

receives regular tidal inundation.
Soil Characteristics 43

Table 11. Soil conductivity in lower tidal forests of the Suwannee River floodplain, Florida 

[See figure 2 for sampling location. EC, electrical conductivity; mmhos/cm, millimhos per centimeter; SP, saturated paste 

extract; Pred EC, calculated from predicted EC using the formula: EC, in mmhos/cm = 1.30 + (2.29 x (Pred EC, in 

mmhos/cm)) - (0.3405 x (bar water, in percent)) (D. Nettleton, Soil Survey Laboratory, National Soil Survey Center, 

Lincoln, Nebraska, written commun., 2000); rkm, river kilometers; cm, centimeters]

Sampling 

location

Distance 

upstream of 

mouth,

in rkm 

Forest 

type

Sampling 

date

Soil sample 

depth,

in cm

Method of 

determining

EC

EC, in 

mmhos/

cm

Estimated 

frequency of 

tidal 

inundation 1

DM-31 4.8 LTsw1 1/11/99 0-25

152-303

SP

Pred EC

2.3

7.9 daily

LK-0 5.1 LTmix 1/11/99 0-20 SP 4.6 daily

LK-64 5.1 LTmix 1/11/99 0-20 SP 4.4 daily

LK-131 5.1 LTsw1 1/11/99 0-20 SP 1.5 daily

BC-67 11.3 LTsw1 3/24/99 0-20

76-91

Pred EC

SP

5.4

5.7 uncommon

BC-139 11.3 LTmix 3/24/99 0-20

89-99

SP

SP

13.7

6.2 uncommon

BC-206 11.3 LTsw2 3/24/99

10-33

102-124

124-137

Pred EC

SP

Pred EC

5.2

6.0

4.7

uncommon

V4-12 11.7 LTsw2 2/9/99 0-20

81-91

Pred EC

SP

2.0

1.1 monthly

V4-10 12.4 LTsw1 2/9/99 0-20

53-79

SP

SP

1.6

2.2 uncommon

SH-0 12.6 LTham 2/9/99 0-20

91-102

Pred EC

SP

4.5

3.9 uncommon

SH-65 12.6 LTham 2/9/99 8-23

91-102

SP

SP

0.9

0.6 uncommon

V4-8 12.7 LTsw1 2/4/99 0-10 Pred EC 0.0 monthly

V4-14 12.9 LTsw2 2/4/99 0-10 SP 1.3 monthly

V4-17 12.9 LTmix 2/4/99 0-10 Pred EC 0.4 monthly

SN-77 13.0 LTmix 2/9/99 0-20

81-127

Pred EC

SP

1.4

2.5 almost daily

V4-9 13.5 LTham 2/4/99 0-10 SP 1.4 uncommon

TK-412 19.8 LTsw1 3/24/99 15-38

97-122

SP

Pred EC

1.2

5.4 monthly

V3-70 19.8 LTsw2 2/3/99 0-10 Pred EC 0.3 none

V3-36 20.0 LTmix 2/3/99 0-10 SP 1.9 none

V3-37 20.0 LTsw1 2/3/99 0-10 SP 1.0 none

V3-33 20.1 LTsw1 2/3/99 0-10 Pred EC 0.0 none

1

Estimated tidal frequency at verification sites is based on proximity to main channel or tidal creeks, and intervening topography apparent on aerial photography.
44 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Higher soil conductivities are a 

result of elevated water salinities in 

these isolated areas (fig. 20) due to 

saline water deposited by storm 

surges and subsequent evaporation. 

Not all forests that are isolated from tidal inundation have 

higher soil conductivities 

(table 11). Factors other than isolation from tides may affect soil conductivity. For instance, shallow 

ground-water flow may remove 

salts from soils in the isolated forest 

at V4-10 where limestone is near 

the land surface (fig. 22). Sand 

dominates the soil profile at SH-65, 

allowing higher percolation rates 

that may remove or flush salts from 

the soil surface during rain events.

Conductivities of subsurface 

soil samples were higher than surface soil samples at 6 of the 

10 locations where both surface and 

-210

-180

-150

-120

-90

-60

-30

0

DM31

(4.8)

LK0

(5.1)

LK64

(5.1)

LK131

(5.1)

BC67

(11.3)

BC139

(11.3)

BC206

(11.3)

V4-

12

(11.7)

V4-

10

(12.4)

SH0

(12.6)

SH65

(12.6)

V4-

8

(12.7)

V4-

14

(12.9)

V4-

17

(12.9)

SN77

(13.0)

V4-

9

(13.5)

TK412

(19.8)

V3-

70

(19.8)

V3-

36

(20.0)

V3-

37

(20.0)

V3-

33

(20.1)

SOIL SAMPLE LOCATION

(River kilometer shown in parentheses)

DEPTH, IN CENTIMETERS

2.0 to 4.0

SOIL CONDUCTIVITY, IN MILLIMHOS PER CENTIMETER

APPROXIMATE

LOWER LIMIT

OF ROOT ZONE

4.0 to 8.0

Greater than 8.0

Not determined

0 to 1.0

1.0 to 2.0

Figure 23. Soil conductivity ranges in lower tidal forests of the Suwannee River, Florida. Soil samples are arranged in order by 

increasing distance from mouth of the river. See figure 2 for sampling location.

subsurface soils were sampled 

(table 11). The subsurface conductivity of 5.4 mmhos/cm at TK 

transect was high considering the 

distance of the transect from the 

Gulf (rkm 19.8). Saline water may 

have been deposited in the swamp 

at TK by exceptionally large storm 

surges, such as those reported in 

1842 and 1882 (Ho and Tracey, 

1975). In a study by Coultas 

(1984), the conductivity of subsurface soils from forested wetlands 

in the lower Apalachicola River 

(6 22 km upstream of the mouth) 

were higher than that of surface 

soils. In that study, conductivities of 

all surface soils were less than 

1.0 mmhos/cm, but subsurface soils 

had an average conductivity of 

2.9 mmhos/cm with a maximum of 

7.7 mmhos/cm at one location. The 

increase in conductivity at greater 

depth was expected because the 

surface tends to be frequently 

flushed with rain and river water 

resulting in a dilution of salts 

(Coultas, 1984).

FOREST COMPOSITION 

AND DISTRIBUTION

The 10-year floodplain of the 

lower Suwannee River contains 

about 18,600 ha that are presently 

or were historically forested 

(fig. 24). About 75 percent of this 

area is wetlands (14,000 ha) and 

25 percent is uplands (4,600 ha). 

Forested wetlands in tidal reaches 

cover nearly twice the area of those 

in the riverine reach, with the greatest area of forested wetlands in the 

lower tidal reach. 
Forest Composition and Distribution 45

Approximately 29 percent 

of the total area of forests has 

been altered for agricultural or 

residential use. Upland forests 

have been altered to a much 

greater extent (63 percent) than 

wetland forests (17 percent). 

Many of the altered uplands are 

cleared of all trees, whereas most 

of the altered wetland forests have 

at least some scattered trees.

A total of 77 tree, shrub, 

and woody vine species were 

identified in the canopy and 

subcanopy of floodplain wetland 

forests (n = 8,376). Canopy 

species included 52 trees and 

1 woody vine. An additional 

16 species of trees and shrubs, 

and 8 woody vine species were 

identified in the subcanopy. In 

this report, importance of a 

species is based on relative basal 

area for canopy species and 

relative density for subcanopy 

species.

659

443

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

AREA, IN HECTARES

UPLAND FORESTS (Riverine and Upper Tidal)

UPPER TIDAL WETLAND FORESTS

RIVERINE WETLAND FORESTS

LOWER TIDAL WETLAND FORESTS

1,681 2,905

4,380

2,850

4,350 1,312

UNALTERED

ALTERED

AREA--In

hectares

2,905

Figure 24. Area of uplands and wetlands that are presently or were historically 

forested in the 10-year floodplain of the lower Suwannee River, Florida. About 

75 percent of upland forests are found in the riverine reach and 25 percent in the 

upper tidal reach. Small areas of upland forests are included in hammocks in the 

lower tidal reach because they could not be differentiated from wetlands on aerial 

photos.

Important Tree Species

Taxodium distichum is the 

most important canopy tree in 

riverine wetland forests (cover 

illustration; table 12). Other important canopy trees include Quercus 

virginiana, Quercus laurifolia, 

Planera aquatica, Liquidambar 

styraciflua, Betula nigra, and Fraxinus caroliniana. The high relative 

basal area and low relative density 

of Quercus virginiana indicates that 

this species has a small number of 

trees with large trunks. Fraxinus 

caroliniana and Carpinus caroliniana have the highest relative densities in the canopy.

Carpinus caroliniana is the 

most common riverine subcanopy 

tree, growing in dense stands in 

canopy openings. Most of the 

important canopy species are not 

well represented in the subcanopy. 

Of the seven most important canopy species listed above, only Fraxinus caroliniana, Betula nigra, and 

Planera aquatica have relative densities in the subcanopy greater than 

2 percent.

Taxodium distichum is the 

most important canopy tree in tidal 

wetland forests (table 12). Other 

important tidal trees include Fraxinus profunda, Nyssa biflora, Nyssa 

aquatica, Sabal palmetto, and 

Quercus laurifolia. Most tidal canopy species with high relative basal 

areas also have high relative densities. Fraxinus profunda is the most 

common tidal subcanopy tree.

Six tidal species are rare or 

absent in riverine wetland forests: 

Sabal palmetto, Persea palustris, 

Myrica cerifera, Fraxinus profunda, Magnolia virginiana, and 

Juniperus silicicola (fig. 25). The 

importance or presence/absence of 

these six tidal species in canopy 

forests at the study sites was used to 

distinguish riverine from tidal 

reaches in this study. The relative 

importance of Nyssa biflora in 

swamps also was used to determine 

the riverine-tidal boundary. Nyssa 

biflora grows in all reaches, but 

occurs primarily in bottomland 

hardwood forests in the riverine 

reach, and in swamps and mixed 

forests in the tidal reaches. 

The presence/absence of 

Magnolia virginiana and Juniperus 

silicicola, and the importance of 

Nyssa aquatica, Nyssa biflora, 

Fraxinus profunda, and Sabal palmetto in the canopy, were used to 

distinguish lower tidal from upper 

tidal forests. Magnolia virginiana 

and Juniperus silicicola are limited 

in distribution in the floodplain to 

the lower tidal reach (fig. 25). 

Nyssa aquatica, an important species in upper tidal swamps, is rare 

below rkm 20. Nyssa biflora and 

Fraxinus profunda are more important in lower tidal than in upper 

tidal forests. The importance of 

Nyssa biflora, Fraxinus profunda, 

Magnolia virginiana, and Sabal 

palmetto increasing with proximity
46 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Table 12. Important canopy and subcanopy species in riverine and tidal wetland forests in the floodplain 

of the lower Suwannee River, Florida 

[Tidal wetland forests include all species in upper and lower tidal reaches. Relative basal area (rba) and (rd) of each species in each 

forest type were weighted by the relative area of the forest type from the forest map, and then combined with rba’s and rd’s from 

all other forest types in the reach or reaches indicated. All canopy species with rba of 2 percent and all subcanopy species with rd 

of 2 percent or more are listed. Canopy tree species have diameter at breast height of 10 centimeters (cm) or greater; subcanopy 

species have dbh of 2-9.9 cm]

Riverine wetland forests

Canopy species

Relative basal 

area,

in percent

Relative 

density,

in percent

Subcanopy species

Relative 

density,

in percent

Taxodium distichum 18.75 10.25 Carpinus caroliniana 21.10

Quercus virginiana 11.86 1.70 Fraxinus caroliniana 12.02

Quercus laurifolia 9.03 5.58 Cephalanthus occidentalis 9.34

Planera aquatica 7.55 6.49 Ilex decidua 6.14

Liquidambar styraciflua 7.07 7.98 Forestiera acuminata 6.14

Betula nigra 6.45 9.20 Celtis laevigata 5.16

Fraxinus caroliniana 5.81 13.62 Vitis rotundifolia 4.92

Nyssa aquatica 4.48 2.45 Betula nigra 4.86

Acer rubrum 4.39 4.70 Cornus foemina 3.71

Carpinus caroliniana 3.69 11.92 Ulmus americana 3.21

Quercus lyrata 3.08 0.89 Vitis cinerea 3.18

Carya aquatica 2.92 1.56 Crataegus marshallii 3.18

Gleditsia aquatica 2.10 2.35 Planera aquatica 2.97

Ulmus americana 2.04 2.47 25 other species 14.08

30 other species 10.78 18.86 Total 100.00

Totals 100.00 100.00

Tidal wetland forests

Canopy species

Relative basal 

area,

in percent

Relative 

density,

in percent

Subcanopy species

Relative 

density,

in percent

Taxodium distichum 19.37 16.56 Fraxinus profunda 22.21

Fraxinus profunda 16.11 18.64 Fraxinus caroliniana 16.06

Nyssa biflora 14.30 13.84 Carpinus caroliniana 11.00

Nyssa aquatica 10.61 6.14 Myrica cerifera 8.85

Sabal palmetto 6.70 6.29 Cephalanthus occidentalis 6.43

Quercus laurifolia 5.63 3.91 Magnolia virginiana 4.46

Liquidambar styraciflua 4.71 5.36 Taxodium distichum 4.06

Acer rubrum 4.67 3.96 Cornus foemina 3.71

Magnolia virginiana 3.63 3.24 Persea palustris 2.75

Pinus taeda 2.01 0.85 Ulmus americana 2.23

32 other species 12.26 21.21 Liquidambar styraciflua 2.04

Totals 100.00 100.00 28 other species 16.20

Total 100.00
Forest Composition and Distribution 47

to the Gulf of Mexico is not unique 

to the Suwannee River and has been 

reported in other river floodplains 

of the southeastern United States 

(Wharton and others, 1982; 

Leitman and others, 1984).

Two common trees of river 

floodplains in north Florida, Nyssa 

aquatica, which occurs in the lower 

Suwannee River floodplain, and 

Nyssa ogeche, which does not, have 

interesting geographical distributions in regard to this study area. 

The distribution of Nyssa aquatica

0 10 20 30 40 50 60 70 80 90 100 110

Carya glabra (11)

Ilex opaca (18)

Nyssa sylvatica (25)

Forestiera acuminata (28)

Planera aquatica (224)

Fraxinus caroliniana (425)

Ulmus crassifolia (10)

Crataegus viridis (31)

Quercus geminata (82)

Gleditsia aquatica (67)

Diospyros virginiana (12)

Nyssa aquatica (308)

Betula nigra (268)

Quercus lyrata (22)

Carya aquatica (49)

Carpinus caroliniana (328)

Quercus virginiana (44)

Pinus taeda (29)

Quercus nigra (58)

Liquidambar styraciflua (356)

Cephalanthus occidentalis (86)

Acer rubrum (240)

Quercus laurifolia (268)

Taxodium distichum (839)

Nyssa biflora (481)

Ulmus americana (156)

Sabal palmetto (224)

Persea palustris (38)

Myrica cerifera (34)

Fraxinus profunda (659)

Magnolia virginiana (131)

Juniperus silicicola (17)

RIVERINE

LOWER

TIDAL

UPPER

TIDAL

RIVER KILOMETERS

SELECTED CANOPY TREE SPECIES

SAMPLED AT STUDY SITE

SEEN AT OBSERVATION SITE

Figure 25. Distribution of selected canopy tree species in relation to distance from the mouth of the Suwannee River, 

Florida. Trees species sampled at study sites are indicated by +. Species seen at observation sites (indicated by o) are 

shown only when they result in a range extension. Total sample size is written in parenthesis after species name.

previously mapped by Fowells 

(1965) and Little (1978) covers 

much of the coastal plain of the 

southeastern United States but not 

the Suwannee River basin. Specimens collected more recently 

(Wunderlin and Hansen, 2000) 

extend the distribution in Florida to 

the lower Suwannee River basin in 

Dixie and Levy Counties. During 

the course of this study, Nyssa 

aquatica was found in floodplain 

forests ranging from approximately rkm 19 to 82 (fig. 25). Nyssa 

aquatica was entirely absent from 

swamps at the CF transect (rkm 

104.3) in habitats seemingly suitable for its occurrence. 

Nyssa ogeche grows in the 

upper Suwannee River basin, but is 

absent from the lower Suwannee 

River basin. Nyssa ogeche occurs in 

southeastern South Carolina, southern Georgia and northern Florida 

(Godfrey, 1988; Wunderlin and 

Hansen, 2000). The southern extent 

of the species (without regard to a 

disjunct population in west central 
48 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Florida) approaches the lower 

Suwannee River basin on the west 

and extends north, skirting the 

study area and extending eastward 

(Fowells, 1965; Little, 1978).

The geographical distribution of Sabal palmetto, described by 

Brown (1973), is limited approximately to the tidal reaches of the 

Suwannee River floodplain. Brown 

(1973) states that viable seeds are 

dispersed by littoral and estuarine 

currents. Negative flows during 

large storm surges might result in an 

upstream extension of the range of 

Sabal palmetto, if other factors such 

as air temperatures and flood depths 

at upstream locations were favorable for the species’ survival.

Forest Type Composition

Fourteen specific forest 

types were defined in the 10-year 

floodplain of the lower Suwannee 

River (table 1). Thirteen are wetland forest types and one is an 

upland forest type. Basic characteristics of the forest types with regard 

to hydrologic conditions, soil textures, and dominant species in the 

canopy are summarized in table 13.

The area of each wetland forest type is presented in figure 26. 

Swamps comprise a greater proportion of tidal wetlands (49-63 percent) than riverine wetlands (34 

percent). Drier forest types, which 

include bottomland hardwoods and 

hammocks, have been altered for 

agricultural or residential use to a 

much greater extent (35 percent) 

than wetter forest types, which 

include swamps and mixed forests 

(5 percent). LTham is by far the 

most altered wetland forest type 

(66 percent).

Table 13. Summary of hydrologic conditions, soil textures, and dominant canopy species of forest types in the 10-year 

floodplain of the lower Suwannee River, Florida

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

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

5 months Clay, muck Taxodium distichumPlanera aquatica

UTblh Flooded average of every 2 years; soils dry quickly after floods 

recede Sand Quercus laurifoliaSabal palmetto

UTmix

Flooded several times a year by very high tides or high river 

flows; 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
Forest Composition and Distribution 49

Oak/pine Uplands

Oak/pine uplands occur in 

both the riverine and upper tidal 

reaches. Canopy and subcanopy 

compositions of oak/pine are presented in tables 14 and 15, respectively. Quercus hemisphaerica, 

Pinus taeda, and Quercus geminata

are the dominant canopy species in 

oak/pine forests based primarily on 

verification plots along with 

transect data from a very small segment of CF. Some of these sites are 

oak scrub forests where Quercus 

geminata is dominant. Only the 

canopy was quantitatively meaUNALTERED FOREST

ALTERED FOREST

76 AREA--In hectares

1,353

1,339

1,041

617

461

1,168

1,060

800

891

51

50

76

213

161

179

1,172

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

LTsw1

LTsw2

LTmix

LTham

Rsw1

Rsw2

Rblh1

Rblh2

Rblh3

AREA, IN HECTARES

30

39

FOREST TYPE

897

1,087

382

484

49

59

313

UTsw1

UTsw2

UTmix

UTblh

21

RIVERINE

UPPER TIDAL

LOWER

TIDAL

Figure 26. Area of wetland forest types in the floodplain of the lower Suwannee 

River, Florida. Stunted Fraxinus profunda forests are included in LTsw1 and 

comprise 27 percent of total unaltered area of that type. Small areas of upland 

forests are included in hammocks in the lower tidal reach because they could not 

be differentiated from wetlands on aerial photos. (One of six verification plots 

mapped LTham was an oak scrub forest.)

sured, so relative densities are not 

given for subcanopy composition.

Riverine Wetlands

In the riverine reach, swamps 

are found in the lowest and wettest 

areas of the floodplain (fig. 15). 

Canopy trees in riverine swamps 

typically are large, buttressed, and 

closely spaced (cover illustration, 

fig. 27). Several differences in tree 

composition exist between Rsw1 

and Rsw2 (tables 14 and 15). Rsw1 

has a substantially lower number of 

canopy and subcanopy species 

compared to Rsw2. Taxodium 

distichum is dominant in the canopy 

of Rsw1, comprising 52 percent of 

the total basal area; whereas, Taxodium distichum and Planera aquatica share dominance in Rsw2. 

Bottomland hardwood species are a 

minor component in the canopy of 

Rsw1, totaling less than 6 percent 

of the total basal area, whereas they 

are a substantial component in the 

canopy of Rsw2, totaling over 

20 percent of the basal area. 

Cephalanthus occidentalis is dominant in the subcanopy of Rsw1, 

comprising 58 percent of the 

density; dominance in the subcanopy of Rsw2 is split between four 

species.
50 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Table 14. Canopy composition in riverine wetlands and oak/pine upland forests in the floodplain of the lower 

Suwannee River, Florida

[Canopy species have diameter at breast height of 10 centimeters or greater. The sum of the relative basal area of dominant species in bold 

type is greater than 50 percent. m2

, square meters; m2/ha, square meters per hectare] 

Species

Relative basal area, in percent

Riverine wetlands Oak/pine

uplands Rsw1 Rsw2 Rblh1 Rblh2 Rblh3

Taxodium distichum 52.31 37.22 13.68 0.03

Nyssa aquatica 22.44 5.36 2.83

Fraxinus caroliniana 8.42 15.68 3.06

Planera aquatica 6.88 19.97 6.20

Salix caroliniana 2.39 0.24

Cephalanthus occidentalis 1.80 0.91 0.46 0.09

Betula nigra 1.56 6.96 8.90 12.02 0.42 4.90

Gleditsia aquatica 1.50 2.02 5.78

Acer rubrum 1.34 3.32 4.84 9.50 2.25 0.81

Carya aquatica 0.80 0.69 7.73 4.29

Ulmus americana 0.29 1.53 5.13 1.90 0.06 0.73

Forestiera acuminata 0.27 0.87 0.69

Quercus lyrata 2.10 9.61 1.05

Diospyros virginiana 1.05 0.02 0.58

Quercus laurifolia 0.89 18.01 22.88 1.26 2.26

Liquidambar styraciflua 0.36 8.66 14.30 11.15 3.97

Carpinus caroliniana 0.36 1.75 6.25 9.97 3.63

Crataegus viridis 0.17 0.84 0.69

Ilex decidua 0.11 0.11 0.09

Ulmus crassifolia 0.07 0.51 0.41 0.79

Salix nigra 0.05

Cornus foemina 0.04 0.06

Celtis laevigata 0.03 0.32 0.20

Nyssa sylvatica 0.34 1.37 3.43 3.11

Quercus nigra 0.22 2.91 4.49 0.82

Myrica cerifera 0.14

Nyssa biflora 0.12 1.88 1.82 1.24

Crataegus flava 0.05

Viburnum obovatum 0.03

Quercus virginiana 16.82 43.19 9.57

Quercus hemisphaerica 1.77 1.04 27.07

Persea palustris 0.59

Ilex opaca 0.15 1.70 4.68

Ulmus alata 0.11 0.35

Vitis cinerea 0.06

Pinus glabra 0.19

Quercus michauxii 6.08

Quercus geminata 7.39 12.21

Carya glabra 2.99 3.00

Persea borbonia 0.65 0.44

Pinus taeda 0.65 17.22

Vaccinium arboreum 0.21 0.10

Ostrya virginiana 0.17

Quercus austrina 0.10 1.25

Magnolia grandiflora 2.36

Cyrilla racemiflora 0.14

Symplocus tinctoria 0.13

Totals 100.0 100.0 100.0 100.0 100.0 100.0

Number of trees sampled 433 378 518 467 328 200

Total area sampled, in m2 4633 5950 10847 10365 7793 3813

Basal area, in m2

/ha 61.8 42.6 34.2 25.1 26.0 20.8

Density, in stems per hectare 934.7 635.3 477.6 450.5 420.9 524.5

Number of species 12 23 26 25 22 22
Forest Composition and Distribution 51

Table 15. Subcanopy composition in riverine wetlands and oak/pine upland forests in the floodplain of the lower Suwannee 

River, Florida

[Subcanopy species have diameter at breast height (dbh) of 2-9.9 centimeters (cm) and are at least 3 meters in height. The sum of the relative densities of 

dominant species in bold type is greater than 50 percent. Relative densities were calculated from transect data and species marked with * are additional 

species found on verification plots. Oak/pine uplands were sampled on verification plots for species presence only. m2

, square meters] 

Species

Relative density, in percent

Riverine wetlands Oak/pine 

Rsw1 Rsw2 Rblh1 Rblh2 Rblh3 uplands

Cephalanthus occidentalis 58.32 9.35 2.91

Fraxinus caroliniana 31.30 22.43 10.32 1.32

Planera aquatica 3.36 9.81 *

Cornus foemina 1.68 5.61 5.29 1.99 1.92

Taxodium distichum 0.92 1.87 2.65 0.66

Betula nigra 0.92 7.01 8.47 4.64 * *

Gleditsia aquatica 0.92 0.93 0.26 *

Nyssa aquatica 0.61 *

Acer rubrum 0.61 1.40 1.32 0.66 * *

Quercus laurifolia 0.46 0.47 4.23 0.66 *

Salix caroliniana 0.15 0.53

Carya aquatica 0.15 0.26 1.32

Cyrilla racemiflora 0.15 0.47 3.44 * * *

Forestiera acuminata 0.15 8.41 14.55 1.99

Toxicodendron radicans 0.15 * *

Bumelia reclinata 0.15 * 0.66

Celtis laevigata * 9.81 9.52 1.32

Ulmus americana * 4.67 2.12 7.95 * *

Quercus lyrata * 0.93 0.53 0.66

Ilex decidua 5.14 6.35 11.26 5.77 *

Vitis cinerea 2.80 1.59 2.65 7.69 *

Berchemia scandens 2.34 *

Carpinus caroliniana 1.87 11.64 33.11 57.69 *

Salix nigra 1.40

Ampelopsis arborea 1.40 1.59 1.99

Liquidambar styraciflua 0.47 3.97 1.99 * *

Campsis radicans 0.47 0.26 *

Quercus nigra 0.47 * 1.32 * *

Crataegus sp. 0.47

Crataegus viridis * * 1.99

Crataegus flava 2.65 *

Ulmus crassifolia 1.59

Vitis sp. 1.06 0.66

Crataegus marshallii 1.06 5.30 9.62 *

Vitis rotundifolia 0.79 6.62 17.31 *

Diospyros virginiana 0.53 * * *

Nyssa biflora 0.26 * *

Viburnum obovatum 0.26 1.32 * *

Myrica cerifera * * *

Ilex opaca 5.96 * *

Vaccinium arboreum 1.99 * *

Magnolia virginiana * *

Pinus glabra * *

Quercus hemisphaerica * *

Ulmus alata * * *

Aesculus pavia *

Amorpha fruticosa * *

Asimina parviflora *

Bignonia capreolata *

Carya glabra * *

Halesia carolina *

Ostrya virginiana *

Persea borbonia * *

Pinus taeda * *

Quercus geminata * *

Sebastiania fruticosa *

Symplocos tinctoria * *

Vaccinium elliottii * *

Vaccinium stamineum * *

Lyonia ferruginea * *

Magnolia grandiflora *

Nyssa sylvatica *

Totals 100.0 100.0 100.0 100.0 100.0

Number of trees sampled 655 214 378 151 52

Total area sampled on transects, in m2 1531 2893 3233 2115 1277

Density, in stems per hectare 4278.2 739.7 1169.2 713.9 407.2

Percent of trees 2-4.9 cm dbh 46.4 49.1 61.9 51.0 51.9

Percent of trees 5-9.9 cm dbh 53.6 50.9 38.1 49.0 48.1

Number of species 19 26 34 36 36 29
52 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

 Variations of the Rsw1 and 

Rsw2 forest types were found in 

the riverine reach. Nyssa aquatica

is absent upstream of rkm 82, but is 

an important tree species in 

swamps downstream of rkm 82. 

Springs found in the riverine reach 

have swamp forests along their 

runs. The area covered by spring 

run swamps is minor and composition of these swamps was not determined in this study. 

Nearly monospecific stands 

of Forestiera acuminata were 

found in the riverine reach 

(fig. 28). In these stands, Forestiera 

acuminata grow in widely spaced 

clumps of multiple trunks, with 

few trunks attaining the diameter of 

canopy-size trees. Forestiera 

acuminata is not found downstream of the MS transect at rkm 

42.5. Forestiera stands may be 

classified as swamps or low bottomland hardwood forests depending on the presence of other canopy 

species.

Low bottomland hardwood 

forests are found on slopes around 

swamps, on low levees, ridges, and 

flats, and in higher elevation depressions (figs. 15 and 29). Rblh1 forests 

have a high proportion of swamp tree 

species in the canopy (26 percent), 

which distinguishes Rhlh1 forests 

from high bottomland hardwood forests (Rblh2 and Rblh3) where 

swamp trees are usually absent. 

Dominance in the Rblh1 canopy is 

shared between five species (more 

than in any other forest type): Quercus laurifolia, Taxodium distichum, 

Quercus lyrata, Betula nigra, and 

Liquidambar styraciflua.Two low 

bottomland hardwood species, Quercus lyrata and Carya aquatica, that 

are important in many other river 

floodplains of the southeastern 

United States (Larson and others, 

1981; Wharton and others, 1982), 

were more important in the canopy 

of Rblh1 forests than in any other 

forest type in this study. Dominance 

in the Rblh1 subcanopy is also 

shared between five species, with 

Forestiera acuminata the most 

important. The subcanopies of 

riverine bottomland hardwood 

forests become increasingly dominated by Carpinus caroliniana as the 

Figure 27. Buttressed trunk of a Taxodium distichum tree growing on the banks of Rock Bluff Spring run in the riverine reach 

of the lower Suwannee River, Florida. Very few trees of this stature have survived logging in the floodplain.
Forest Composition and Distribution 53

forests become drier, from 12 percent 

in Rblh1 to 58 percent in Rblh3.

High bottomland hardwoods 

(Rblh2 and Rblh3) are found primarily on high levees, ridges, and flats 

where soils are usually sandy. 

Quercus laurifolia, Quercus virginiana, and Liquidambar styraciflua are 

Figure 28. Clumps of Forestiera acuminata trees in the riverine reach of the 

lower Suwannee River floodplain, Florida. This species usually has multiple 

trunks arching away from the center of the clump and sometimes touching the 

ground. It commonly grows in nearly pure stands with few trunks attaining the 

diameter of canopy-size trees.

Figure 29. Carya aquatica with a flared base growing in Rblh1 forest at the LL 

transect in the lower Suwannee River floodplain, Florida. This area slopes 

gradually from the back of the river levee to a swamp. Carya aquatica was more 

important in Rblh1 than in any other forest type in this study.

dominant in the canopy of Rblh2 

(table 14, fig. 30). Quercus virginiana

comprises 43 percent of the basal 

area of canopy trees in Rblh3 (table 

14, fig. 31). Quercus virginiana trees 

have large crowns visible on aerial 

photos, giving most Rblh3 forests a 

distinctive signature. No subcanopy 

trees of Quercus virginiana were 

found in this study, although there 

may be saplings present that did not 

meet the dbh criteria of 2 cm. In a 

variation of the Rblh3 forest type, 

Quercus michauxii is an important 

canopy tree, sharing dominance with 

or replacing Quercus virginiana.
54 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Figure 30. Rblh2 forest in winter on the MS transect in the lower Suwannee River 

floodplain, Florida. Quercus laurifolia trees shown in the foreground are one of the 

dominant trees in Rblh2.

Figure 31. Large Quercus virginiana in high bottomland hardwood forest in the 

riverine reach of the lower Suwannee River floodplain, Florida. High flats are 

inundated only during large floods, but inundation usually lasts long enough to kill 

upland tree species.
Forest Composition and Distribution 55

Upper Tidal Wetlands

Upper tidal swamps are 

found at elevations below MMH, 

and usually have surface soils 

consisting of saturated mucks 

(table 13). The height of swollen 

bases in upper tidal swamps is 

shorter than in riverine swamps due 

to shallower flooding (fig. 32). 

Nyssa aquatica and Taxodium 

distichum dominate the canopy of 

UTsw1, and share canopy dominance with Fraxinus profunda in 

Figure 32. Swollen bases of Nyssa aquatica and Taxodium distichum in UTsw1 forest at the MS transect in the lower 

Suwannee River floodplain, Florida. Swollen trunks of Nyssa (left) are usually bottle-shaped whereas Taxodium trunks (right) 

have skirt-like bases with narrow flares.

UTsw2 (table 16). Bottomland 

hardwood trees are more important 

in the canopy of UTsw2 

(24 percent) than in UTsw1 (6 percent). Nyssa aquatica is more abundant in the canopy of upper tidal 

swamps than in riverine or lower 

tidal swamps, and comprises over 

75 percent of total relative basal 

area at some verification plots.

Fraxinus caroliniana and 

Cephalanthus occidentalis are the 

most important subcanopy trees in 

upper tidal swamps (table 17). The 

subcanopy of UTsw2 consists of a 

substantially higher number of 

species (30) than the subcanopy of 

UTsw1 (18).

Canopy composition in upper 

tidal swamps varies with topographic position. Variations of 

UTsw1 or UTsw2 forest types 

occur adjacent to the river or on 

tidal streams, with greater proportions of Nyssa biflora and Fraxinus 

profunda found in these forests than 

in isolated swamps.
56 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Table 16. Canopy composition in upper tidal wetland forests 

in the floodplain of the lower Suwannee River, Florida

[Canopy tree species have diameter at breast height of 10 cm or greater. 

The sum of the relative basal area of dominant species in bold type is 

greater than 50 percent. m2

, square meters; m2/ha, square meters per 

hectare] 

Species

Relative basal area, in percent

UTsw1 UTsw2 UTmix UTblh

Nyssa aquatica 45.86 25.22 3.74

Taxodium distichum 27.17 23.80 27.95 1.70

Fraxinus profunda 9.66 8.43 18.56 3.57

Nyssa biflora 4.42 5.49 4.03 0.69

Planera aquatica 4.20 7.48

Fraxinus caroliniana 2.70 4.93 0.61

Liquidambar styraciflua 2.69 2.85 10.75 12.61

Acer rubrum 1.16 5.01 3.81 4.43

Gleditsia aquatica 0.80 2.15 0.07

Ulmus americana 0.43 1.86 2.67 1.96

Betula nigra 0.39 5.56 2.95 3.27

Carya aquatica 0.20 2.63 2.07

Salix caroliniana 0.14 0.32 0.43

Sabal palmetto 0.10 0.38 3.19 22.75

Cephalanthus occidentalis 0.05 0.35

Ilex cassine 0.03

Quercus laurifolia 2.75 15.96 29.73

Quercus lyrata 0.24 1.73

Crataegus flava 0.16

Diospyros virginiana 0.14

Crataegus viridis 0.10 0.22 0.22

Forestiera acuminata 0.07

Carpinus caroliniana 0.03 1.18 4.63

Cornus foemina 0.03

Ulmus crassifolia 0.31

Myrica cerifera 0.12 0.36

Viburnum obovatum 0.08

Quercus geminata 4.59

Quercus virginiana 4.34

Quercus nigra 4.25

Lyonia ferruginea 0.29

Ulmus alata 0.19

Totals 100.0 100.0 100.0 100.0

Number of trees sampled 471 565 231 197

Total area sampled, in m2 4896 5898 3456 3828

Basal area, in m2

/ha 70.0 57.6 51.3 24.6

Density, in stems per hectare 962.0 958.0 668.4 514.6

Number of species 16 23 19 18

Table 17. Subcanopy composition in upper tidal wetland 

forests in the floodplain of the lower Suwannee River, Florida

[Subcanopy species have diameter at breast height (dbh) of 2-9.9 

centimeters (cm) and are at least 3 meters in height. The sum of the relative 

densities of dominant species in bold type is greater than 50 percent. 

Relative densities were calculated from transect data and species marked 

with * are additional species found on verification plots. m2

, square meters]

Species Relative density, in percent

UTsw1 UTsw2 UTmix UTblh

Fraxinus caroliniana 70.21 44.81 9.29 *

Cephalanthus occidentalis 12.16 28.77 5.71 *

Planera aquatica 5.17 5.19 0.71

Cornus foemina 3.95 1.89 6.43 *

Taxodium distichum 2.74 5.19 1.43 *

Toxicodendron radicans 1.52 1.42 * *

Acer rubrum 0.91 * 0.71 *

Ulmus americana 0.91 0.47 5.71 *

Liquidambar styraciflua 0.61 * 9.29 3.57

Nyssa aquatica 0.61 0.94 *

Quercus laurifolia 0.30 * 10.71 3.57

Carya aquatica 0.30 * *

Quercus lyrata 0.30 0.47 0.71 *

Vitis rotundifolia 0.30 1.43 *

Fraxinus profunda * 1.42 * *

Nyssa biflora * *

Myrica cerifera * * *

Betula nigra 2.36 3.57 5.36

Ulmus crassifolia 1.89 5.71 *

Gleditsia aquatica 1.42 2.14

Forestiera acuminata 1.42

Ampelopsis arborea 0.94 0.71

Bumelia reclinata 0.47

Crataegus sp. 0.47 1.43 *

Ulmus sp. 0.47

Carpinus caroliniana * 22.14 85.71

Itea virginica * 7.14

Vitis cinerea * * *

Ilex cassine *

Viburnum obovatum * *

Styrax americanum * *

Amorpha fruticosa 3.57

Berchemia scandens 0.71

Vitis sp. 0.71

Crataegus viridis *

Decumaria barbara *

Ilex decidua *

Diospyros virginiana 1.79

Rhus copallina *

Quercus nigra *

Persea palustris *

Crataegus marshallii *

Cyrilla racemiflora *

Lyonia ferruginea *

Quercus geminata *

Quercus myrtifolia *

Ulmus alata *

Vaccinium arboreum *

Vaccinium stamineum *

Sabal palmetto1 * * * *

Totals 100.00 100.00 100.00 100.00

Number of trees sampled 329 212 140 56

Total area sampled, in m2 3616.1 2484 499.4 322

Density, in stems per hectare 909.8 853.5 2803.4 1739.1

Percent of trees 2-4.9 cm dbh 34.0 28.3 77.1 78.6

Percent of trees 5.0 - 9.9 cm dbh 66.0 71.7 22.9 21.4

Number of species 18 30 29 32

1

Sabal palmetto was either too large in dbh or too short to be a subcanopy tree. It was seen in all UT forest types, and may have been 

important in UTblh where it was a dominant canopy tree. 
Forest Composition and Distribution 57

Upper tidal mixed forests 

are found on low levees and flats 

or in transitional areas on the 

edges of swamps (fig. 33). Dominance in the UTmix canopy is 

shared by Taxodium distichum, 

Fraxinus profunda and Quercus 

laurifolia. Nyssa aquatica is much 

less important in the canopy of 

UTmix than in UTsw1 and UTsw2, 

although the relative basal area of 

Taxodium distichum is similar in all 

three types. Fraxinus profunda is a 

swamp species that is more important in the canopy of UTmix than in 

UTsw1 or UTsw2. Fraxinus profunda can tolerate continuously saturated soils, but is probably less 

tolerant of deep inundation during 

floods, and may have an advantage 

for survival on the slightly higher 

elevations in UTmix forests.

Dominance in the subcanopy 

of UTmix is shared by four species, 

with Carpinus caroliniana the most 

important. Two dominant subcanopy species in Rblh1, Forestiera 

Figure 33. UTmix forest on the KI transect in the lower Suwannee River 

floodplain, Florida. The water line on trees, which appears to be about a meter 

above ground level, can be created by stained bark, the presence of bryophytes 

such as Porella pinnata, or the absence of light-colored lichens below flood 

elevations. Water lines are lower in forests of the upper tidal reach than the 

riverine reach due to shallower flooding.

acuminata and Celtis laevigata, are 

absent in UTmix.

Upper tidal bottomland hardwood forests are found on sandy 

soils on high flats and in transitional areas between upland forests 

and swamps. 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 (fig. 15). 

The canopy of UTblh forests is 

dominated by Quercus laurifolia

and Sabal palmetto. Carpinus caroliniana becomes increasingly dominant in the subcanopy of upper tidal 

forests as the hydrologic conditions become drier. This species is 

nearly absent in upper tidal swamps, 

and has a relative density of 86 percent in the subcanopy of UTblh.

Lower Tidal Wetlands

Lower tidal swamps are 

found on deep muck soils that 

are below the elevation of the 

MMH or MDH. Lower tidal 

swamps typically have denser 

ground-cover than swamps in 

other reaches, probably due to 

shallower flood depths (fig. 5). 

Fraxinus profunda, Taxodium

distichum, and Nyssa biflora are 

the most important canopy species, 

constituting 83 percent of the total 

basal area in LTsw1 and 

72 percent in LTsw2 (table 18). 

The greatest difference in the 

canopy composition of these 

swamp types is the importance of 

Fraxinus profunda (33 percent in 

LTsw1 compared to 18 percent in 

LTsw2), which may account for 

the different signatures of the two 

types on aerial photographs. 

Fraxinus profunda is dominant in 

the subcanopy of LTsw1 and 

shares dominance with Magnolia 

virginiana in LTsw2 (table 19). 

LTsw2 forests are found on stream 

banks more commonly than 

LTsw1 forests, which may result in 

a different dominance pattern 

within the same set of species.
58 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Table 18. Canopy composition in lower tidal wetland forests 

in the floodplain of the lower Suwannee River, Florida

[Canopy tree species have diameter at breast height of 10 cm or greater. 

The sum of the relative basal area of dominant species in bold type is 

greater than 50 percent. m2

, square meters; m2/ha, square meters 

per hectare]

Species

Relative basal area, in percent

LTsw1 LTsw2 LTmix LTham

Fraxinus profunda 33.04 18.27 18.96 0.69

Taxodium distichum 26.08 21.91 11.83 1.28

Nyssa biflora 23.40 31.76 15.33 1.59

Acer rubrum 5.45 5.01 8.55 0.96

Liquidambar styraciflua 3.26 2.32 5.00 8.87

Nyssa aquatica 2.70 2.05

Magnolia virginiana 2.30 4.83 14.25 2.81

Ulmus americana 1.48 3.10 2.46 1.17

Sabal palmetto 1.23 2.63 12.64 27.79

Quercus laurifolia 0.53 4.17 5.85 7.52

Taxodium ascendens 0.15 2.85

Salix caroliniana 0.08 0.16

Juniperus silicicola 0.07 0.04 0.84 2.61

Persea palustris 0.07 2.04 1.17

Carpinus caroliniana 0.06 0.14 0.40 5.79

Myrica cerifera 0.05 0.06 1.28 0.07

Ilex cassine 0.03 0.08 0.05

Pinus elliottii 0.73

Gleditsia aquatica 0.06

Quercus virginiana 0.35 6.11

Pinus taeda 0.10 23.30

Quercus nigra 0.04 6.01

Cephalanthus occidentalis 0.03

Quercus geminata 1.57

Diospyros virginiana 0.16

Ostrya virginiana 0.12

Vitis cinerea 0.09

Quercus myrtifolia 0.08

Celtis laevigata 0.07

Totals 100.0 100.0 100.0 100.0

Number of trees sampled 643 493 682 270

Total area sampled, in m2 5195 4261 6281 4694

Basal area, in m2

/ha 59.0 57.6 52.1 26.4

Density, in stems 

per hectare 1237.7 1157.1 1085.9 575.2

Number of species 17 17 18 23

Table 19. Subcanopy composition in lower tidal wetland 

forests in the floodplain of the lower Suwannee River, Florida

[Subcanopy species have diameter at breast height (dbh) of 2-9.9 centimeters (cm) and are at least 3 meters in height. The sum of the relative 

densities of dominant species in bold type is greater than 50 percent. 

Relative densities were calculated from transect data and species marked 

with * are additional species found on verification plots. m2

, square meters]

Species

Relative density, in percent

LTsw1 LTsw2 LTmix LTham

Fraxinus profunda 50.94 34.55 41.54 *

Myrica cerifera 17.92 7.27 22.43 10.42

Taxodium distichum 6.60 5.45 2.94 2.08

Ulmus americana 4.72 3.64 * 2.08

Magnolia virginiana 3.77 18.18 2.57 *

Nyssa biflora 2.83 * 2.21

Cornus foemina 1.89 9.09 2.57 2.08

Liquidambar styraciflua 1.89 1.82 * 6.25

Persea palustris 1.89 7.27 4.78 4.17

Juniperus silicicola 1.89 2.57 2.08

Toxicodendron radicans 0.94 2.21

Acer rubrum 0.94 1.82 0.74 2.08

Gleditsia aquatica 0.94

Carpinus caroliniana 0.94 5.45 2.57 29.17

Vitis sp. 0.94 1.82 0.74 2.08

Ilex vomitoria 0.94 0.74 *

Cephalanthus occidentalis * * 1.84 *

Smilax laurifolia * * 

Quercus laurifolia * 1.82 4.04 2.08

Ilex cassine * * 1.47 4.17

Viburnum obovatum * 1.47 2.08

Vitis rotundifolia 1.82 * 12.50

Itea virginica *

Vaccinium corymbosum * 4.17

Diospyros virginiana 1.10

Vitis cinerea 0.74 2.08

Fraxinus caroliniana 0.37 *

Baccharis glomeruliflora 0.37

Quercus nigra 6.25

Ostrya virginiana 4.17

Ampelopsis arborea *

Lyonia ferruginea *

Quercus geminata *

Pinus taeda *

Quercus chapmanii *

Sabal palmetto 1 * * * *

Totals 100.0 100.0 100.0 100.0

Number of trees sampled 106 55 272 48

Total area sampled, in m2 1019.4 782.4 1201.5 755

Density, in stems per hectare 1039.8 703.0 2263.8 635.8

Percent of trees 2-4.9 cm dbh 58.5 45.5 62.1 56.3

Percent of trees 5.0 - 9.9 cm dbh 41.5 54.5 37.9 43.8

Number of species 22 18 25 28

1 Sabal palmetto was either too large in dbh or too short to be a subcanopy tree. It was seen in all LT forest types, and may have been important in LTham where it was a dominant canopy tree.
Forest Composition and Distribution 59

Stunted stands of Fraxinus 

profunda are a common variant of 

LTsw1 forests, comprising 27 percent 

of the total area of LTsw1 forest 

(fig. 34). Stunted stands of Fraxinus profunda were distinguished 

on aerial photographs by a unique 

signature, but were not quantitatively sampled or surveyed for 

elevation. Stunted swamps may 

have scattered individuals or 

sparse overstories of slightly 

taller Taxodium distichum trees. 

Tree stunting is barely perceptible 

at rkm 17.9, gradually increases 

downstream, and is severe in 

stands at the tree line where 

canopy heights average 5-6 m. 

Annual rings counted on a stunted 

Fraxinus profunda tree growing 

Figure 34. 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 m tall.

at rkm 4.0 that was 11 cm in 

diameter indicated an age of 

about 122 years (Clewell and 

others, 1999). The uniformity of 

tree heights observed in stunted 

stands may be evidence that these 

stands are composed of even-aged 

trees growing where previous 

forests have been destroyed by a 

large storm surge, such as occurred 

in 1882.

Lower tidal mixed forests 

include swamps with numerous 

small hummocks or few large 

hummocks, and transitional areas 

between swamps and hammocks. 

LTmix forests (fig. 35) are found 

on saturated muck soils that are 

below the elevation of the MMH 

or MDH except for hummock 

tops. Fraxinus profunda, Nyssa

biflora and Magnolia virginiana

are dominant canopy species in 

LTmix. Magnolia virginiana trees 

have a unique signature that 

distinguishes LTmix forests on 

aerial photographs. This species 

is commonly observed in the 

field growing on the edges of 

hummocks or close to stream 

channels. Magnolia virginiana 

trees growing on the mud floor 

of lower tidal swamps can be 

slightly elevated by their own 

gnarled roots, which can form an 

elevated, tangled root mat 

(fig. 36). The sub-canopy of type 

LTmix is dominated by Fraxinus 

profunda and Myrica cerifera.
60 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Figure 35. LTmix forest at SN transect, which receives regular tidal inundation 

from a small tributary of Sandfly Creek in the lower Suwannee River floodplain, 

Florida. Fiddler crabs, which are indicators of tidal conditions, are common at this 

site.

Figure 36. Root mat on the bank of East Pass in the lower Suwannee River, 

Florida. In the lower tidal reach, the roots of Magnolia virginiana and other trees 

sometimes form an elevated, tangled root mat on banks and hummock edges that 

can be described as “armored.”
Forest Composition and Distribution 61

Lower tidal hammocks in the 

Suwannee River floodplain are part 

of the Gulf Coastal Hammocks as 

described by Vince and others 

(1989). LTham forests are found on 

higher elevations that do not receive 

regular tidal inundation or frequent 

Figure 37. Sabal palmetto and Pinus taeda dominate the canopy of hammocks in 

the lower tidal reach of the Suwannee River floodplain, Florida. This hammock at 

the SH transect had large Osmunda cinnamomea clumps in the ground cover.

river flooding, but have a high 

water table and are inundated by 

storm surges or river floods several 

times a decade (fig. 16). LTham 

forests are dominated by Sabal palmetto and Pinus taeda (fig. 37). 

Attempts to grow Pinus taeda commercially on hammocks in the 

floodplain have altered tree composition on many sites.

The dominant LTham subcanopy species are Carpinus 

caroliniana, Vitis rotundifolia, and 

Myrica cerifera. Young Sabal 
62 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

palmettos were found in all tidal 

communities and are probably 

important in LTham subcanopy; the 

plants measured in this study were 

too large in diameter at a height of 

3 m to be considered subcanopy 

trees, and therefore were not 

included in subcanopy density 

calculations.

Figure 38. Sabal palmetto trees growing on slightly higher ground in a marsh on East Pass in the lower Suwannee River, 

Florida. Sabal palmetto is one of the most salt-tolerant tree species. Most trees at or downstream of the tree line are stunted; 

the tallest palms in this photo are about 12 m in height.

Lower tidal hammocks vary in 

distance from the Gulf and in elevation, and therefore, in exposure to 

river flooding, storm surges, seasonal 

high tides, and salinity. Hammocks 

located closest to the Gulf of Mexico 

contain the highest proportions of 

Sabal palmetto (fig. 38). Large tree 

islands surrounded by marshes downstream of the tree line are maritime 

hammocks, some of which are overgrown Indian shell middens (Carr, 

1983). These hammocks support 

some tree species not found in this 

study such as Bumelia lanuginosa, 

Tilia caroliniana, and Osmanthus 

americana (Clewell and others, 

1999).
Forest Composition and Distribution 63

Characteristics of Forest 

Type Composition

Species richness in the canopy and subcanopy of forests of the 

lower Suwannee River floodplain is 

high compared to other river floodplains in North America. Eight of 

the 13 wetland forest types in this 

study had 30 or more canopy and 

subcanopy species, and two forest 

types (Rblh2 and Rblh3) had 40 or 

more species (fig. 39). In 15 forest 

types on 5 other river floodplains of 

north Florida, the highest number 

of species was 31 in the high bottomland hardwood forest type of 

the Apalachicola River; all other 

types ranged from 6 to 25 species 

(Leitman and others, 1984; Light 

and others, 1993). In numerous 

other studies throughout North 

America reviewed by Brinson 

(1990), the number of species in 

riverine forest types rarely 

exceeded 25.

CANOPY SPECIES

ADDITIONAL

SUBCANOPY SPECIES

11 NUMBER OF SPECIES 17

17

18

23

16

23

19

18

12

23

26

25

22

22

8

6

10

11

6

10

12

7

15

20

17

7

10

11

0 10 20 30 40 50

oak/pine

NUMBER OF SPECIES

FOREST TYPES

RIVERINE

UPPER

TIDAL

LOWER

TIDAL

RIVERINE AND

UPPER TIDAL

LTsw1

LTsw2

LTmix

LTham

UTsw1

UTsw2

UTmix

UTblh

Rsw1

Rsw2

Rblh1

Rblh2

Rblh3

Figure 39. Species richness of canopy and subcanopy 

trees in floodplain forests of the lower Suwannee River, 

Florida.

In riverine wetland forests, 

the number of canopy and subcanopy species increases consistently 

from the lowest elevation swamps 

(19 species in Rsw1) to the highest 

elevation bottomland hardwoods 

(42 species in Rblh3). As elevation 

increases, depth and duration of 

inundation decrease, improving 

conditions for tree growth and 

allowing a greater number of tree 

species to become established. This 

trend is typical of almost all 

riverine forests (Brinson, 1990), 

and is also generally true for tidal 

forests in this study.

The opposite trend occurs 

with basal area of canopy trees per 

hectare, which decreases with 

increasing elevation (fig. 40). In all 

reaches, basal area was greatest in 

swamps, 43-70 square meters per 

hectare (m2

/ha), and lowest in high 

bottomland hardwoods and hammocks, 25-26 m2

/ha. In a review by 

Brinson (1990), riverine swamps in 

southern states averaged 62 m2

/ha 

basal area; however, data collection 

methods varied. Upper and lower 

tidal forests generally have higher 

average basal area per hectare than 

riverine forests.

The average size of canopy 

trees is smaller in the lower tidal 

reach than in the riverine or upper 

tidal reaches (fig. 41). Smaller tree 

size, however, is offset by a higher 

density of canopy trees (figs. 42 

and 43), which accounts for the relatively high basal area of canopy 

trees of lower tidal swamps. The 

canopy of oak/pine upland forests 

has less than the average density, 

the smallest average tree size, and 

the lowest basal area of all forest 

types. This could be the result of 

fires, logging, grazing, and other 

disturbances that occur more frequently in upland than in wetland 

forests.

59

58

52

26

70

58

51

25

62

43

34

25

26

21

0 10 20 30 40 50 60 70 80

LTsw1

LTsw2

LTmix

LTham

UTsw1

UTsw2

UTmix

UTblh

Rsw1

Rsw2

Rblh1

Rblh2

Rblh3

oak/pine

BASAL AREA, IN

SQUARE METERS PER HECTARE

FOREST TYPES

RIVERINE

UPPER

TIDAL

LOWER

TIDAL

RIVERINE AND

UPPER TIDAL

BASAL

AREA PER

HECTARE

52

Figure 40. Basal area of canopy trees in floodplain 

forests of the lower Suwannee River, Florida.
64 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

AVERAGE

BASAL AREA

PER TREE

477

0 100 200 300 400 500 600 700 800 900

477

498

480

459

727

601

768

478

661

671

717

557

617

397

UTmix

LTsw1

LTsw2

LTmix

LTham

UTsw1

UTsw2

UTblh

Rsw1

Rsw2

Rblh1

Rblh2

Rblh3

oak/pine

FOREST TYPES

AVERAGE BASAL AREA PER TREE,

IN SQUARE CENTIMETERS

RIVERINE

UPPER TIDAL

LOWER TIDAL

RIVERINE AND

UPPER TIDAL

Figure 41. Average size of canopy trees in floodplain 

forests of the lower Suwannee River, Florida.

Figure 43. Dense stand of trees in LTsw1 forest on DM transect in the lower 

Suwannee River floodplain, Florida. Canopy trees have high densities in lower 

tidal swamps, averaging 1,200 trees per hectare, although the average tree size 

is less than in swamps in upper tidal and riverine reaches.

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

oak/pine

LTsw1

LTsw2

LTmix

LTham

UTsw1

UTsw2

UTmix

UTblh

Rsw1

Rsw2

Rblh1

Rblh2

Rblh3

NUMBER OF CANOPY TREES

PER HECTARE

FOREST TYPES

1,238

1,157

1,086

575

962

958

668

515

935

635

478

451

421

525

RIVERINE

UPPER TIDAL

LOWER TIDAL

RIVERINE AND

UPPER TIDAL

NUMBER OF

TREES PER

HECTARE

478

Figure 42. Density of canopy trees in floodplain forests of 

the lower Suwannee River, Florida.
Forest Composition and Distribution 65

Subcanopy density is much 

higher in type Rsw1 (4,278 stems 

per hectare) than in any other forest 

type (fig. 44). High values for canopy basal area and canopy density 

indicate that the subcanopy density 

in Rsw1 is not related to lack of 

canopy. High subcanopy density is 

also not due to multiple-trunked 

trees (common in swamps) because 

trees with trunks joined at or above 

the tree base were counted as one 

tree in density calculations. The 

high density of Cephalanthus 

occidentalis, the most common 

subcanopy tree in Rsw1, may be 

related to a lack of fire in these 

swamps. Cephalanthus occidentalis

was found to be dominant in areas 

of a south Florida swamp that had 

been logged, but not dominant in 

areas that had been logged and 

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

NUMBER OF SUBCANOPY TREES

PER HECTARE

RIVERINE

UPPER TIDAL

LOWER TIDAL

1,040

703

2,264

636

910

853

2,803

1,739

4,278

740

1,169

714

407

LTsw1

LTsw2

LTmix

LTham

UTsw1

UTsw2

UTmix

UTblh

Rsw1

Rsw2

Rblh1

Rblh2

Rblh3

FOREST TYPES

NUMBER OF

TREES PER

HECTARE

703

Figure 44. Density of subcanopy trees in floodplain forests 

of the lower Suwannee River, Florida. Subcanopy of oak/pine 

was not sampled for density.

burned (Gunderson, 1986). In tidal 

reaches, mixed forests have the 

highest densities of subcanopy 

trees.

Canopy trees with multiple 

trunks are more common in 

swamps than in other forest types in 

the same reach (fig. 45). Deep 

flooding may cause trees to produce more basal sprouts (Davis, 

1990). Both the density of multiple 

trunks in swamps and the depth of 

flooding decrease downstream from 

the riverine to the lower tidal reach. 

Canopy tree species with more than 

one-third of their trees having multiple trunks were Forestiera acuminata (71 percent), Fraxinus 

caroliniana (53 percent), Crataegus 

viridis (42 percent), Ilex opaca

(39 percent) and Planera aquatica

(35 percent). Only 3 percent of all 

Taxodium distichum trees sampled 

had multiple trunks, but at the CF 

transect, 11 of 68 trees (16 percent) 

had multiple trunks. These trees 

had been logged and the bases had 

resprouted, producing multipletrunked trees with an average basal 

area of 2,060 square centimeters 

(cm2

), over twice as large as the 

average size of single-trunked Taxodium distichum at CF (988 cm2

). 

Basal sprouting by this species after 

logging is rare, but may have been 

successful at this site due to the 

absence of Nyssa aquatica, which 

is more prolific than Taxodium 

distichum with regard to basal 

sprouting (Putnam, 1960) and may 

inhibit sprouting of other species by 

shading. 

0 50 100 150 200 250

32

53

73

83

26

55

156

32

33

80

182

233

oak/pine 60

118

LTham

LTmix

LTsw2

LTsw1

UTblh

UTmix

UTsw2

Rblh3

Rblh2

Rblh1

Rsw2

Rsw1

UTsw1

NUMBER OF MULTIPLE-TRUNKED

CANOPY TREES PER HECTARE

FOREST TYPES

RIVERINE

UPPER TIDAL

LOWER TIDAL

RIVERINE AND

UPPER TIDAL

NUMBER OF

TREES PER

HECTARE

73

Figure 45. Density of multiple-trunked canopy trees in 

floodplain forests of the lower Suwannee River, Florida.
66 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Snags are denser in lower 

tidal swamps, averaging 46 snags 

per hectare, than in all other forest 

types, averaging 18 snags per hectare (fig. 46). The density of snags is 

higher than average at most lower 

tidal transects and exceptionally 

high at TK (83 snags per hectare). 

Higher densities of snags on 

transects in the lower tidal reach 

may be the result of changing conditions related to sea level rise or 

saline water deposited by recent 

storm surges. 

FLOW-DEPENDENT 

CHARACTERISTICS 

OF FLOODPLAIN

In this section, hydrologic 

characteristics of the floodplain 

forest that are related to river flow 

are described to provide the foundation for assessing impacts of potential flow reductions.

LTham

LTmix

LTsw2

LTsw1

UTblh

UTmix

UTsw2

Rblh3

Rblh2

Rblh1

Rsw2

Rsw1

UTsw1

18

0 10 20 30 40 50 60

19

25

54

37

21

14

14

19

16

16

15

11

oak/pine

27

NUMBER OF CANOPY-SIZE SNAGS

PER HECTARE

FOREST TYPES

RIVERINE

UPPER TIDAL

LOWER TIDAL

RIVERINE AND

UPPER TIDAL

NUMBER OF

SNAGS PER

HECTARE

14

Figure 46. Density of canopy-size snags in floodplain 

forests of the lower Suwannee River, Florida.

Inundation and Saturation

During low and medium 

flows, inundated areas in floodplain 

forests provide aquatic habitat for 

fish and wildlife that is different 

from the main river channel and 

tributaries. Floodplain ponds and 

sloughs are shallow, still-water 

habitats under the forest canopy. By 

comparison, channels of spring 

runs and the Suwannee River have 

open waters that are usually deeper 

and flowing more swiftly. During 

high flows, flooded forests provide 

important aquatic habitat for main 

channel fishes. In addition, nutrients and detritus in the floodplain 

forest carried downstream by 

flowing waters provide a valuable 

food source for aquatic organisms 

in the river and estuary.

Saturation is important in 

maintaining the character of organic 

soils because oxygen depletion 

occurs when soils are saturated, and 

decomposition of organic matter is 

slowed when oxygen is absent 

(Mitsch and Gosselink, 2000). Oxidation of organic matter can occur 

relatively rapidly in soils desiccated 

by drainage (Gleason, ed., 1974; 

Johnson, 1974).

In floodplain forests of the 

riverine reach, the amount of inundated and saturated area is dependent upon river flow (figs. 47 and 

48, app. VI). In this report, saturated areas include inundated areas, 

meaning that an area is considered 

to be saturated both when soils are 

saturated and exposed, and when 

surface water covers the ground. 

For any given flow, the amount of 

water in the floodplain varies 

depending upon the amount of 

antecedent rainfall, time elapsed 

since the last flood, antecedent 

evapotranspiration rates, and connection to ground water. Estimates 

presented in figures 47 and 48 represent the average inundated and 

saturated areas, respectively, existing under a variety of conditions at 

any given flow.

At or below median flow 

(181 m3

/s; 6,480 ft3/s), nearly 

all inundated and most saturated 

areas in riverine forests are found 

in swamps. Water levels in ponds 

and sloughs in riverine swamps 

decrease in response to decreasing river levels, even when they 

are isolated from the main river 

channel. The generally good 

hydraulic connection between 

water in the swamp and the river 

at low and medium flows may be 

due to the high permeability of 

subsurface sands and limestone. 

Water levels in some swamps are 

higher than river levels at low and 

medium flows because of local 

rainfall, residual flood waters, 

ground-water seepage from adjacent uplands, or hydraulic connection to the Floridan aquifer. 
Flow-Dependent Characteristics of Floodplain 67

Total

Rblh1

Total

Rsw1/sw2

Rblh2/blh3

Most Areas

Not Flowing

Most Areas

Flowing

B

Rblh1

Rsw1/sw2

Rblh2/blh3

75% Exceedance Flo

w

25% Exceedance Flo

w

Median Flo

w

2-Year, 1-Day High Flo

w

5-Year, 1-Day High Flo

A w

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

5,500

100 200 300 400 500 600 700 800 900 1,000

FLOW, IN CUBIC METERS PER SECOND

INUNDATED AREA, IN HECTARES

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000

FLOW, IN CUBIC FEET PER SECOND

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

5,500

0 100 200 300 400 500 600 700 800 900 1,000

FLOW, IN CUBIC METERS PER SECOND

INUNDATED AREA, IN HECTARES

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000

FLOW, IN CUBIC FEET PER SECOND

0

Some

Areas

Flowing

Figure 47. Estimated amount of 

inundated area in riverine wetland 

forests in relation to flow in the lower 

Suwannee River, Florida, showing 

(A) selected long-term river flow 

statistics (1933-99) and (B) flow 

ranges for water movement through 

the floodplain. Flow is combined flow 

of Suwannee River at Branford and 

Santa Fe River near Fort White. 

Inundated areas of specific forest 

types Rsw1, Rsw2, Rblh2, and Rblh3 

are not shown, but can be calculated 

by multiplying percentages in 

appendix VI by the forest type areas 

shown in figure 26.
68 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

The potentiometric surface of the 

Floridan aquifer slopes from the 

adjacent uplands towards the river 

channel (Fisk and Rosenau, 1977; 

Rosenau and Milner, 1986; 

Rosenau and Meadows, 1986; 

Meadows, 1991; Mahon and others, 1997). The potentiometric surface is lowered when river flows 

are low, decreasing the amount of 

standing water and saturated soils 

in riverine swamps.

At river flows below about 

291 m3

/s (10,400 ft3/s), most inundated areas in the riverine reach are 

not flowing (fig. 47). These areas 

are either isolated from the river or 

are connected but have no downstream outlet. As river levels rise, 

waters backed up from the river in 

some areas of the floodplain find 

downstream outlets and begin to 

flow. When river flows reach about 

386 m3

/s (13,800 ft3/s), most of the 

inundated area in the riverine reach 

is flowing downstream through the 

floodplain.

Duration of inundation and 

saturation associated with each 

riverine forest type is shown in 

figure 49. The amount of time that 

the ground is inundated or saturated is an important factor affecting survival of tree species. 

Oxygen can be depleted in soils 

within a few hours or days after 

becoming saturated (Ponnamperuma, 1972). Anoxic conditions 

result in the death of root tips of 

many plants. Upland and high bottomland hardwood trees will not 

survive if the soils are saturated for 

long periods during the growing 

season (Hosner and Boyce, 1962; 

Gill, 1970). The root systems, however, of swamp species and some 

low bottomland hardwood species 

have physiological adaptations that 

allow them to survive anoxic conditions in saturated soils (Hook and 

Brown, 1973). Flooded conditions 

are generally unfavorable for plant 

growth, but saturated conditions 

benefit swamp species by reducing 

competition from flood-intolerant 

species.

The longest durations of 

inundation and saturation in 

riverine forests occur in swamps. 

Median percent duration of inundation is estimated to be 59 percent 

(about 7 months a year) for Rsw1 

forests, and 32 percent (about 

Total

Rblh2/blh3

Rsw1/sw2

Rblh1

75% Exceedance Flo

w

25% Exceedance Flo

w

Median Flo

w

2-Year, 1-Day High Flo

w

5-Year, 1-Day High Flo

w

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

4,500

5,000

5,500

0 100 200 300 400 500 600 700 800 900 1,000

FLOW, IN CUBIC METERS PER SECOND

SATURATED AREA, IN HECTARES

0 5,000 10,000 15,000 20,000 25,000 30,000 35,000

FLOW, IN CUBIC FEET PER SECOND

Figure 48. Estimated amount of saturated area in riverine wetland forests in 

relation to flow in the lower Suwannee River, Florida. Saturated conditions exist 

both during inundation and when saturated soils are exposed. Flow is combined 

flow of Suwannee River at Branford and Santa Fe River near Fort White. Long-term 

river flow statistics are based on 1933-99 record. Saturated areas of specific forest 

types Rsw1, Rsw2, Rblh2, and Rblh3 are not shown, but can be calculated by 

multiplying percentages in appendix VI by the forest type areas shown in figure 26.
Flow-Dependent Characteristics of Floodplain 69

4 months a year) for Rsw2 forests 

(fig. 49). Median percent duration 

of saturation is estimated to be 

100 percent for Rsw1 forests, and 

70 percent (about 8 months a year) 

for Rsw2 forests.

Rblh1 forests are typically 

inundated 16 percent of the time 

EXPLANATION

MEDIAN

MAXIMUM

MINIMUM

75th PERCENTILE

25th PERCENTILE

MAXIMUM, 75th PERCENTILE,

MEDIAN, AND

25th PERCENTILE

MINIMUM

Inundation Saturation

Rsw1

Rsw1/sw2

Rsw2

Rblh1

Rblh2

Rblh2/blh3

Rblh3

Rsw1

Rsw1/sw2

Rsw2

Rblh1

Rblh2

Rblh2/blh3

Rblh3

FOREST TYPE

0

10

20

30

40

50

60

70

80

90

100

DURATION OF INUNDATION OR SATURATION,

IN PERCENT OF TIME

Figure 49. Duration of inundation and saturation of riverine forest types in the 

floodplain of the lower Suwannee River, Florida. Branford-Fort White flows at 

which the minimum, 25th percentile, median, 75th percentile and maximum area 

of each forest type was inundated or saturated were determined from appendix VI 

and converted to durations using 1933-99 flow duration analysis. Data for specific 

forest types (Rsw1, Rsw2, Rblh2, and Rblh3) were weighted by the proportion of 

the area they covered in the forest map before they were combined to create data 

for general forest types (Rsw1/sw2 and Rblh2/blh3).

(average of 2 months a year), and 

are saturated 26 percent of the time 

(3 months). Many Rblh1 forests 

stay saturated after they are no 

longer inundated because the forests 

are located on the edge of depressional features in clay soils that tend 

to retain water after floods recede.

Rblh2/blh3 forests are commonly found on levees or ridges 

with sandy soils that dry quickly 

after floods recede, so there is little 

difference between duration of 

inundation and saturation for these 

forests. Duration of inundation of 

Rblh2/blh3 forests was about 

5 percent over the 67-year period of 

record (1933-99). Floods on the 

Suwannee River are relatively 

irregular, therefore Rblh2/blh3 forests are not flooded at all during 

many years, and then are subjected 

to relatively long periods of inundation during some years. For example, there have been nine floods 

since 1933 in which river stage has 

exceeded the median elevation of 

Rblh2/blh3 continuously for 6 weeks 

or longer. These floods occurred in 

the fall of 1947 and the spring of 

1948, 1959, 1965, 1973, 1983, 

1984, 1987, and 1998 (fig. 50).

In the upper tidal reach, 

nearly all inundated and saturated 

areas existing at low and medium 

flows are found in swamps, many 

of which are isolated from regular 

tidal inundation. The amount of 

inundated and saturated area in 

relation to flow in the upper tidal 

reach was not calculated for low 

and medium flows, because inundated and saturated conditions in 

isolated swamps in the upper tidal 

reach are not as dependent on river 

flow as swamps in the riverine 

reach. Although limestone may not 

be far below the floodplain floor, 

the extensive mucky soils in upper 

tidal swamps probably interfere 

with the hydraulic connection 

between isolated ponds and the 

river. Land-surface elevations in 

upper tidal swamps are close to the 

elevation of the MDH and mucky 

soils stay saturated regardless of 

river flow. At a high flow of about 

310 m3

/s (11,000 ft3/s), almost all 

upper tidal swamps are submerged 
70 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

and connected to the river, and 

water begins to flow slowly downstream through the floodplain. At 

the 2-year, 1-day high flow of 

568 m3

/s (20,290 ft3/s), almost all 

remaining upper tidal wetland forests are covered with flowing water. 

In lower tidal forests, the amount of 

inundated and saturated area is 

unrelated to flow during low and 

medium flows, and only weakly 

related to flow at high flows.

Flood Depths

Flooding prevents or severely 

restricts the establishment of tree 

seedlings. Most tree seeds, including those of swamp species, do not 

germinate in water (DeBell and 

Naylor, 1972); and for the few 

seeds that do, it is unlikely that any 

substantial number of seedlings can 

survive and successfully establish 

themselves in submerged soils 

(DuBarry, 1963). After seeds germinate on exposed soils, their 

growth depends on many factors, 

including tolerance of soil saturation, available sunlight, herbivory, 

and competition. Seedlings will 

die, however, if the next flood overtops them for extended periods. 

Total submergence of leaves and 

stems that continues for 10-20 days 

is fatal to seedlings of many swamp 

and bottomland hardwood species 

(Demaree, 1932; Hosner, 1960). 

Tree seedlings that are not completely submerged have a higher 

survival rate; therefore seedlings 

that can grow tall quickly are more 

likely to survive flooding. Two 

important species in riverine 

swamps, Taxodium distichum and 

Nyssa aquatica, are among the 

fastest growing seedlings, with the 

potential to exceed 1 m in height in 

1-2 years (Harms, 1973; Brown, 

1984). Most other tree seedlings 

are less than 1 m tall at 2 years of 

age, even when grown under controlled conditions (Fowells, 1965; 

Conner and Askew, 1993). Saplings 

gain height more rapidly than seedlings, so mortality due to flooding 

is less likely after the first 5 years in 

the life of a young tree.

Based on the above-mentioned studies of tree seedling 

growth, flood depths maintained 

continuously for a period of 

14 days that occur every 2 to 

5 years were determined to be 

important descriptors of general 

historical flood conditions affecting 

tree regeneration in riverine and 

upper tidal forests (fig. 51). These 

frequently occurring floods restrict 

regeneration in wetland forests 

because seedlings are unable to 

gain enough height during the intervening period to survive the next 

flood. Larger floods are usually 

less important to tree regeneration 

because they occur less frequently, 

allowing more time for young trees 

to reach heights that will exceed 

flood depths.

The flood depth maintained 

continuously for 14 days at a frequency of once every 2 years was 

Figure 50. Floodwaters more than 3 meters deep during the 25-year flood in 

1998 in a bottomland hardwood forest near the FK transect in the lower 

Suwannee River floodplain, Florida.

determined to be about 1.5 m for 

the median elevation in Rsw1 forests (fig. 51). If 2-year events actually occurred every 2 years without 

fail, regeneration in Rsw1 forests 

would be extremely limited because 

regular and frequent floods with 

depths exceeding 1 m for 14 days 

or more would prevent regeneration 

of nearly all trees, regardless of 

species. Flood recurrence intervals, 

however, are probabilities calculated from historic records, and the 

actual frequencies of floods are not 

necessarily regular. Any long 

period of record will include periods of severe drought in which 

floods do not occur for several 

years. Much of the regeneration in 

Rsw1 forests begins with seedlings 

established during periods of severe 

drought, and flood depths immediately following the end of a drought 

will determine which saplings 

survive.

Most Rblh2/blh3 and UTblh 

forests are continuously flooded 

for 14 days in the 5-year flood, but 

not in the 2-year flood (fig. 51). 

Although many tree seedlings could
Flow-Dependent Characteristics of Floodplain 71

Land surface

Land surface

2 year,

14-day flood

5 year,

14-day flood

FLOODED

NOT FLOODED

FLOODED

NOT FLOODED

MAXIMUM

MINIMUM

75th PERCENTILE

25th PERCENTILE

MEDIAN

EXPLANATION

FOREST TYPE

-1.5

-1.0

-0.5

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0

Rsw1

Rsw1/sw2

Rsw2

Rblh1

Rblh2

Rblh2/blh3

Rblh3

Rsw1

Rsw1/sw2

Rsw2

Rblh1

Rblh2

Rblh2/blh3

Rblh3

-1.0

-0.5

0

0.5

1.0

1.5

2.0

UTsw1

UTsw1/sw2

UTsw2

UTmix

UTblh

UTsw1

UTsw1/sw2

UTsw2

UTmix

UTblh

DIFFERENCE BETWEEN RIVER STAGE AND LAND SURFACE, IN METERS

FOREST TYPE

RIVERINE

2-year, UPPER TIDAL

14-day flood

5-year,

14-day flood

Figure 51. Flood depths in riverine and upper tidal forest types in the floodplain of 

the lower Suwannee River, Florida. Flood depths are the maximum depth 

maintained continuously for 14 consecutive days for the recurrence interval 

indicated (1933-99). Data for specific forest types (Rsw1, Rsw2, Rblh2, Rblh3, 

UTsw1, and UTsw2) were weighted by the proportion of the area they covered in 

the forest map before they were combined to create data for general forest types 

(Rsw1/sw2, Rblh2/blh3, and UTsw1/sw2).

attain sufficient height in four or 

five growing seasons to survive the 

5-year flood depth of about 0.5 m, 

seedlings of most upland species 

would be killed because they are 

intolerant of 14 days of inundation, 

regardless of the depth of the water. 

Flood depths decrease from 

the riverine to the lower tidal reach 

for all forest types (fig. 52). During 

a 2-year event, lower tidal forests are 

probably flooded every day at high 

tide, but flooding is not continuous 

for 14 days because the ground is 

exposed every day at low tide. Flood 

depths in swamps of the LL transect 

are less than those at other riverine 

transects (fig. 52A) because many 

LL swamps are maintained by both 

continuous saturation from a small 

floodplain spring and inundation 

from river flooding.

Differences in 5-year flood 

depths between the reaches (fig. 52) 

are important in determining the 

distribution of tidal species in relation to distance from the Gulf 

(fig. 25) and locations of reach 

boundaries for swamps, low bottomland hardwoods, and mixed forests. Tidal species such as 

Magnolia virginiana, Fraxinus 

profunda, and Persea palustris are 

typically found in swamps with 

very shallow flooding (Monk, 

1966; Clewell, 1986; Light and others, 1993; Herring and Judd, 1995). 

Seedlings of Nyssa biflora grow 

more slowly than those of Nyssa

aquatica (Harms, 1973). Nyssa 

biflora grows well in tidal swamps 

(UTsw1/sw2 and LTsw1/sw2) and 

in low bottomland hardwoods of 

the riverine reach (Rblh1) where 

median depths in the 5-year, 14-day 

flood are less than 2 m. Nyssa 

biflora, however, does not grow in 

riverine swamps (Rsw1/Rsw2) 

where depths are greater than 2 m 

in the 5-year, 14-day flood.

Most young trees that survive 

flooding their first 5 years of life are 
72 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

-1

0

1

2

3

4

FLOODED

NOT FLOODED

Land Surface

UPPER RIVERINE

TIDAL

LOWER

TIDAL

-1

0

1

2

3

4

0 10 20 30 40 50 60 70 80 90 100 110

DISTANCE FROM RIVER MOUTH, IN KILOMETERS

C. HIGH BOTTOMLAND HARDWOODS AND HAMMOCKS

Inset shown

in figure 55

B. LOW BOTTOMLAND HARDWOODS AND MIXED FORESTS

FLOODED

NOT FLOODED

Land Surface

UPPER RIVERINE

TIDAL

LOWER

TIDAL

EXPLANATION

25-YEAR, 14-DAY FLOOD

5-YEAR, 14-DAY FLOOD

2-YEAR, 14-DAY FLOOD

TRANSECTS:

CF

LL

FK

MS

KN and KI

TK

SN and SH

LK and DM

DIFFERENCE BETWEEN RIVER STAGE AND LAND SURFACE, IN METERS

-1

0

1

2

3

4

FLOODED

NOT FLOODED

Land Surface

UPPER RIVERINE

TIDAL

LOWER

TIDAL

A. SWAMPS

Figure 52. Flood depths in wetland forests in the floodplain of the lower Suwannee River, Florida, in relation to 

distance from river mouth. Flood depths are shown for the median elevation of the indicated forest type at each site 

and represent 14 days of continuous flooding for the indicated recurrence interval (1933-99). High bottomland 

hardwoods and hammocks are not inundated in the 2-year, 14-day flood at any sites. Reach boundaries in A are 

different than in B and C, because the floodplain from rkm 37 to 45.2 is a transitional area in which the bottomland 

hardwood forests are part of the riverine reach and the swamp forests are part of the upper tidal reach.
Flow-Dependent Characteristics of Floodplain 73

unlikely to be completely submerged in subsequent floods. For 

example, riverine swamp trees 

25 years of age have the potential to 

be much taller than the flood depths 

of 3 to 4 meters that occur in a 25-

year event (fig. 52). A notable 

exception to this may be Sabal 

palmetto, which is an important canopy species in UTblh and LTham. 

Young Sabal palmetto sometimes go 

through a long establishment phase 

of 30-60 years during which time 

they lack an above-ground stem or 

trunk (McPherson and Williams, 

1996). As a result, larger floods 

occurring at recurrence intervals of 

25 years or more probably restrict 

regeneration of Sabal palmetto to 

the higher elevations in tidal reaches 

of the floodplain.

Salinity

Most tree seedlings are 

stressed by salinities greater than 

3 ppt and are killed by salinities 

greater than 10 ppt in surface water 

or interstitial soil water in greenhouse experiments (Pezeshki and 

others, 1987; McKee and Mendelssohn, 1989; Pezeshki and 

others, 1990; Perry and Williams, 

1996; McCarron and others, 1998; 

Williams and others, 1998). High 

salinities can stress or kill mature 

trees as well (Penfound and 

Hathaway 1938; Kjerfve, 1976; 

B. McPherson, U.S. Geological 

Survey, written commun., 1997). 

Penfound (1952) reported that the 

transition from 4 to 6 ppt for “average salinity of soil water” was 

assumed to be responsible for the 

location of the tree line in swamps 

and marshes of the southeastern 

United States.

In the lower Suwannee River, 

water salinities at high tide at the 

tree line during low flow commonly 

approach or exceed the lethal limit 

of tolerance for trees and tree seedlings. Surface and vertically averaged salinities at the tree line in 

West Pass are typically greater than 

10 ppt at low flow (Tillis, 2000). 

The tree line is slightly farther from 

the Gulf in West Pass (rkm 2.4) 

than in East Pass (rkm 2.1), which 

is probably a reflection of the 

higher salinities in West Pass than 

in East Pass (Mattson and Krummrich, 1995). Typical surface salinities have not been determined in 

East Pass due to insufficient data, 

but vertically averaged salinities at 

the tree line in East Pass are also 

typically greater than 10 ppt at low 

flow.

At medium flows, vertically 

averaged salinities are greater than 

5 ppt at the tree line in West Pass 

and range between 2 and 5 ppt at 

the tree line in East Pass. At high 

flows, river water is fresh (less than 

0.5 ppt) at the tree lines in both 

West and East Passes. Surface soils 

increase in salinity during low-flow 

periods and decrease in salinity 

when they are flushed with fresh 

water during high flows (Clewell 

and others, 1999). Soil salinities 

probably reflect the combined 

effects of water salinities under all 

flow conditions.

It is not known whether tree 

mortality defining the coastward 

limit of trees is a result of shortterm, high-salinity events (e.g., prolonged drought or hurricane storm 

surge); or long-term average conditions. Both are probably important, 

and ideally, both types of data 

would be useful in estimating 

potential impacts of flow reductions 

on tree mortality at the tree line. 

Little salinity data are available for 

extreme events, however, and 

salinity data sufficient to describe 

typical long-term conditions are 

also somewhat limited. Water salinities in relation to river flow based 

on multiple linear-regression models of vertically averaged salinities 

at medium flow (Tillis, 2000) were 

the data used in this report to estimate potential movement of the tree 

line if flows were reduced. 

Because of insufficient data, salinity-flow relations based on lowflow conditions were used for 

descriptive purposes, but were not 

used to calculate estimated impacts 

of flow reductions.

In addition, surface salinity 

measurements probably represent 

conditions in tidal forests better 

than vertically averaged measurements; however, Tillis (2000) was 

unable to determine typical surface 

salinities in relation to flow because 

of insufficient data. Surface and 

vertically averaged salinity data are 

related, and relative changes in vertically averaged salinities at the tree 

line were used in this report to estimate impacts of flow reductions.

Throughout most of the lower 

tidal reach upstream of the tree line, 

occasional deposition of saline 

water from storm surges influences 

the composition of the forest by preventing the establishment of saltintolerant species. Some riverine 

species with downstream distribution limits in the lower tidal reach 

are sensitive to low levels of salinity. Nyssa aquatica may not tolerate any salinity (Penfound and 

Hathaway, 1938). Nyssa aquatica is 

dominant in upper tidal swamps of 

the Suwannee River floodplain 

(table 16), but disappears from 

lower tidal swamps below rkm 17 

(fig. 25). It is possible that bottomland hardwood species such as Betula nigra, Quercus lyrata, Carya 

aquatica, and Carpinus caroliniana, 

which do not grow in the Suwannee 

River floodplain downstream of 
74 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

rkm 10 (fig. 25), may be restricted 

by salinity. Studies reporting the 

impact of salinity on these species, 

however, could not be found in the 

scientific literature to confirm this 

assumption, and other factors, such 

as a change in soils from the upper 

to lower tidal reach, could also be 

restricting the species distribution. 

LTham and LTmix forests have 

more muck in surface soils (fig. 22) 

and more soil saturation (table 10) 

than UTblh and UTmix forests. Liquidambar styraciflua was not found 

on the lower Suwannee floodplain 

downstream of rkm 7 and is probably restricted by salinity. In a greenhouse study, some Liquidambar 

styraciflua seedlings were able to 

tolerate 2 ppt salinity, but nearly all 

died at 4 ppt (Williams and others, 

1998). 

Gradually increasing salinity 

from upstream to downstream in 

the lower tidal reach creates advantageous conditions for a number of 

salt-tolerant species. Nyssa bifora

was common in swamps near the 

tree line, and individuals were 

occasionally observed in marshes 

downstream of the tree line 

(Clewell and others, 1999), 

although not as far downstream as 

the river mouth. In a greenhouse 

study, all Nyssa bifora seedlings 

died after 1 month of flooding with 

10 ppt salinity water (McCarron 

and others, 1998). Taxodium distichum tolerated salinities varying 

from 3 to 10 ppt in several different 

studies (Penfound and Hathaway 

1938; Pezeshki and others, 1987; 

Allen and others, 1997; B. McPherson, U.S. Geological Survey, written commun., 1997). Occasional 

mature, stunted Taxodium distichum trees were observed in the 

marsh near the river mouth during 

the data collection period; however, 

many of those trees later died as 

severe drought conditions of 1999 

continued through the summer of 

2000 (S. Tomlinson, U.S. Geological Survey, oral commun., 2000). 

Sabal palmetto and Juniperus silicicola are among the most salt-tolerant trees based on greenhouse 

experiments (Perry and Williams, 

1996; Williams and others, 1998). 

Both of these species grow on hammocks throughout the lower tidal 

reach and on tree islands in the 

marsh below the tree line of the 

Suwannee River floodplain 

(fig. 38). Fraxinus profunda

appears to be highly salt tolerant as 

well, based on its abundance 

throughout the lower tidal reach 

and in isolated patches in the marsh 

areas downstream of the tree line.

POTENTIAL IMPACTS OF 

FLOW REDUCTIONS

Water use in the Suwannee 

River basin in Florida and Georgia 

is expected to increase over time 

because of anticipated growth and 

development in the region and adjacent areas. Increased consumption 

of water, supplied primarily from 

ground-water sources, could reduce 

ground-water discharge to the 

Suwannee River and decrease river 

flows. Flow reductions in turn, 

could affect hydrologic conditions 

in the forested floodplain, resulting 

in changes in forest composition, 

soil characteristics, biogeochemical processes, and fish and wildlife 

habitat characteristics.

Changes in Floodplain 

Forest Composition

The composition of forest 

communities in the floodplain is 

dependent upon river flow. If flows 

were reduced, hydrologic conditions would become drier in riverine and upper tidal forests, and 

more saline in lower tidal forests, 

resulting in changes to the forest 

composition. Forest composition 

changes may not be evident for 

decades because, in most cases, 

hydrologic changes would have a 

greater effect on the survival of 

seedlings and saplings than on 

mature trees.

In this report, reductions in 

river flow are assumed to cause an 

existing forest type to change to a 

different existing type containing 

drier, more tidal, or more salt-tolerant species. There is no certainty, 

however, that forests will change to 

an existing native type. Reductions 

in flow could provide opportunities 

for exotic species to invade, or 

could support a different mix of 

native species. Deviations from 

existing forest types would be more 

likely if flow reductions were large 

and if hydrologic changes occurred 

over a relatively short time period 

(Kjerfve, 1976; Brinson and others, 

1981; Light and Darst, 1997). 

Change to Drier Forest Types

Each forest type is associated 

with a particular range of durations 

of inundation and saturation in the 

riverine reach, and flood depths in 

the riverine and upper tidal reaches 

(figs. 49 and 51). Permanent longterm reductions in flow would 

result in a decrease in long-term 

duration of inundation and saturation associated with each riverine 

forest type. An example of this 

potential decrease in duration is 

illustrated in figure 53, in which 

existing long-term duration of inundation for Rsw1/sw2 forests is 

compared to hypothetical durations 

if flows were reduced. Flood frequency flows would also decrease 

if flows were reduced, resulting in 

shallower flood depths for each forest type in the riverine and upper 

tidal reaches. 

For each hypothetical flow 

reduction, the estimated amount of 

change in hydrologic conditions of 
Potential Impacts of Flow Reductions 75

-2.8

-8.4

-14.0

-28.0

-56.0

(-100)

(-300)

(-500)

(-1,000)

(-2,000)

EXISTING DURATION CURVE

HYPOTHETICAL FLOW REDUCTION

-In cubic meters per

second (cubic feet per second)

DURATION CURVE

Flow at which 50 percent

of Rsw1/sw2 forests are inundated

20 22 24 26 28 30 32 34 36 38 40

PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED

FLOW, IN CUBIC METERS PER SECOND

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

FLOW, IN CUBIC FEET PER SECOND

0

50

100

150

200

250

300

350

400

27.5 percent

32.4 percent

35.3 percent

36.6 percent38.0 percent

38.6 percent

Figure 53. Estimated decreases in duration of inundation for Rsw1/sw2 forests if flows were reduced in the lower 

Suwannee River, Florida. Flow durations were based on Branford-Fort White flows (1933-99). Duration curves were 

enlarged from those presented in appendix VII, which cover flows up to 700 cubic meters per second (24,720 cubic feet 

per second). The flow at which 50 percent of Rsw1/sw2 forests are inundated was derived from appendix VI, using data 

for Rsw1 and Rsw2 forest types that were weighted by the proportion of the area they covered in the forest map before 

they were combined to create data for the general forest type Rsw1/sw2.

a particular forest type can be quantified as the percentage change 

toward the existing hydrologic conditions of the next drier forest type. 

The amount of change in Rsw1/sw2 

hydrology toward the hydrology of 

Rblh1 forests resulting from flow 

reductions was compared using 

four statistical measures listed in 

table 20: duration of inundation; 

duration of saturation; 2-year, 

14-day flood depths; and 5-year, 

14-day flood depths. These measures were selected as important 

hydrologic factors determining the 

amount of bottomland hardwoods 

that could become established and 

survive in Rsw1/sw2 forests. If 

these long-term hydrologic statistics were changed as a result of permanent long-term flow reductions, 

conditions would become drier in 

Rsw1/sw2 forests and bottomland 

hardwood species would invade. 

The percentage of Rsw1/sw2 

forest area expected to convert to 

Rblh1 forests if flows were reduced 

was estimated using the percentage 

change in long-term hydrologic 

conditions. For example, if flows 

were reduced 56 m3

/s (2000 ft3/s), 

then changes in duration of inundation or saturation suggest that 50 or 

47 percent, respectively, of 

Rsw1/sw2 forests would change to 

Rblh1 (table 20). However, 2-year 

or 5-year flood depths, which are 

also important in determining forest 

composition, suggest a smaller 

change of 37 or 25 percent, respectively. It is possible that swamps 

that have dried substantially with 

regard to duration of inundation and 

saturation might still be maintained 

primarily as swamps if floods were 

still deep enough to prevent the 

invasion of bottomland hardwood 

species. Similarly, some bottomland hardwood seedlings that survive 2-year flood depths might not 

survive the greater 5-year flood 

depths, which would not change as 

much from flow reductions. The 

percentages of forest type changes 

shown in table 21 are minimum 

estimates because they are based on 

the factor most resistant to change 

(5-year, 14-day flood depth).
76 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Table 20. Comparison of four different measures of long-term hydrologic conditions used to calculate hydrologic 

changes in riverine swamps resulting from hypothetical flow reductions in the lower Suwannee River, Florida

[Existing conditions are in black type; changes due to hypothetical flow reductions are in red type. Hydrologic statistics are based on analysis of 

1933-99 Branford-Fort White flow. m3

/s, cubic meters per second; ft3/s, cubic feet per second; %, percent.

Example calculation for percent shift in median duration of inundation of Rsw1/sw2 toward that of next drier forest type (Rblh1) if flows are 

reduced by 56 m3

/s (2,000 ft3/s): (38.6% - 27.5%) / (38.6% - 16.3%) = 49.8%

Example calculation for percent shift in median 2-year, 14-day flood depth of Rsw1/sw2 toward that of next drier forest type (Rblh1) if flows are 

reduced by 56 m3

/s (2,000 ft3/s): (1.30 m - 1.01 m) / (1.30 m - 0.51 m) = 37.4% Discrepancies in calculation results are due to rounding.]

Shift in hydrology of 

Rsw1/sw2 toward that of 

next drier forest type (Rblh1) 

for indicated hydrologic statistic

Forest type

Flow condition for period of 

record

(1933-99)

Median duration Median flood depth, 

in meters Median duration Median flood depth

InundationSaturation2-year, 14-

day high1

5-year, 14-

day high1

InundationSaturation

2-year, 

14-day 

high1

5-year, 

14-day 

high1

Rsw1/sw2 Existing 38.6%2 80.7% 1.30 2.42

Hypothetical flow 

reduction, in m3

/s 

(ft3

/s)

-2.8 (-100) 38.0%2 79.0% 1.29 2.41 2.7% 3.1% 1.9% 1.2%

-8.4 (-300) 36.6%2 75.6% 1.26 2.39 9.0% 9.3% 5.3% 3.8%

-14 (-500) 35.3%2 72.7% 1.23 2.37 14.8% 14.6% 9.2% 6.0%

-28 (-1,000) 32.4%2 66.0% 1.16 2.31 27.8% 26.9% 18.3% 12.1%

-56 (-2,000) 27.5%2 55.1% 1.01 2.21 49.8% 46.8% 37.4% 24.8%

Rblh1 Existing 16.3% 26.0% 0.51 1.56

1

 Flood depths were calculated using the threshold discharge of the 2-year or 5-year, 14-day high stage. 2

 See figure 53 for an example illustrating how these durations were calculated.

Table 21. Percent of forest types estimated to change to next drier type if flows were reduced in the lower Suwannee 

River, Florida

[Existing conditions are in black type; changes due to hypothetical flow reductions are in red type. m3/s, cubic meters per second; ft3/s, cubic feet 

per second; %, percent]

Original 

forest

type

Next drier 

forest

type

Flood depths or water-surface elevations below land surface 

during 5-year, 14-day high, in meters1 Amount of original forest type

estimated to change to next drier 

type for indicated hypothetical flow 

reduction, in m3

/s (ft3/s) Under 

existing 

conditions 

for original 

forest type

Under hypothetical flow reductions, in 

m3

/s (ft3/s), for original forest type

Under 

existing 

conditions 

for next 

drier type

-2.8 

(-100)

-8.4

(-300)

-14.0

(-500)

-28.0

(-1000)

-56.0

(-2000)

-2.8

(-100)

-8.4

(-300)

-14.0

(-500)

-28.0

(-1000)

-56.0

(-2000)

Rsw1/sw2 Rblh1 2.42 2.41 2.39 2.37 2.31 2.21 1.56 1.2% 3.8% 6.0% 12.1% 24.8%

Rblh1 Rblh2/blh3 1.56 1.55 1.53 1.51 1.46 1.35 0.48 0.8% 2.8% 4.6% 9.3% 18.9%

Rblh2/blh3 Upland 0.48 0.47 0.45 0.43 0.38 0.28 -1.08 0.6% 1.9% 3.2% 6.4% 13.0%

UTmix UTblh 0.92 0.91 0.90 0.88 0.85 0.78 0.44 1.3% 4.4% 7.5% 14.5% 28.9%

UTblh Upland 0.44 0.43 0.41 0.40 0.37 0.30 -0.84 0.5% 1.7% 2.9% 5.5% 11.0%

1

 Flood depths were calculated using the threshold discharge of the 5-year, 14-day high stage.
Potential Impacts of Flow Reductions 77

Area of forest types 

expected to change to the next 

drier type (fig. 54) is determined 

from the percent change (table 21) 

and the total area of each forest 

type (fig. 26). In the riverine reach, 

flow reductions would result in 

greater changes in swamps than in 

bottomland hardwood forests, 

based on both proportional change 

(table 21) and area change (fig. 

54). Estimates of the impacted 

area of riverine bottomland hardwood forests are greater than that 

of upper tidal mixed forests and 

bottomland hardwoods primarily 

because of the greater total area of 

the riverine bottomland hardwood 

forests (fig. 26).

UTblh

UTmix

Rblh2/blh3

Rblh1

Rsw1/sw2

0

50

100

150

200

250

300

350

400

450

AREA OF FOREST

0 10 20 30 40 50 60

TYPE ESTIMATED TO CHANGE

TO NEXT DRIER TYPE, IN HECTARES

0 500 1,000 1,500 2,000

HYPOTHETICAL FLOW REDUCTION,

IN CUBIC METERS PER SECOND

HYPOTHETICAL FLOW REDUCTION,

IN CUBIC FEET PER SECOND

Figure 54. Area of forest types estimated to change to next drier type if flows 

were reduced in the lower Suwannee River, Florida. Flow reductions were 

subtracted from Branford-Fort White flows.

Change to drier forest types 

resulting from flow reductions is 

not expected for UTsw1/sw2 

forests. If flows were reduced in 

the upper tidal reach, flood depths 

in those forests would decrease, 

but the duration of saturation in 

swamps would likely change very 

little. Most upper tidal swamps 

have mucky soils that stay continuously saturated because the soils 

are below the elevation of the 

MMH (fig. 15). Bottomland hardwood and hammock species would 

be unlikely to invade areas with 

saturated mucks, even if flood 

depths became shallow enough for 

those species to become established.

Change to drier forest types 

resulting from flow reductions is 

not expected for LTsw1/sw2, 

LTmix, and LTham forests. 

Decreases in flood depths would 

be minor if flows were reduced 

because the relation of stage to 

flow in most of the lower tidal 

reach is poor. Mucky soils in 

swamps would probably remain 

saturated because of their low elevation with respect to the MMH. 

Hammocks grow under a relatively 

wide range of hydrologic conditions and might not change to 

another forest type if hydrologic 

conditions changed only slightly. 

In addition, sea level rise may 

offset the slightly drier conditions 

that could occur if flows were 

reduced.

Upstream Movement of tIdal 

Forests

Many tidal species are 

restricted by flood depths that 

increase with distance from the 

mouth of the river (figs. 25 and 

52), consequently preventing most 

tidal forest types from becoming 

established upstream of the existing reach boundaries. If flows 

were reduced, flood depths that 

limit establishment of tidal species 

would occur farther upstream. As 

a result, tidal species would invade 

upstream of existing reach boundaries, creating new boundary locations between riverine and upper 

tidal reaches, and between upper 

and lower tidal reaches.

An example calculation of 

the upstream movement of a reach 

boundary (between Rblhl and 

UTmix forests) is graphically 

depicted in figure 55 and mapped 

in figure 56. The distances that 

three tidal forest types are 
78 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

estimated to move upstream are 

listed in table 22. Water depths 

during all frequently occurring 

floods (with recurrence intervals 

from 2 to 5 years) are important in 

restricting the establishment of 

tidal species in swamps, low bottomland hardwoods, and mixed 

forests. It is possible, however, 

that some seedlings that survive 

2-year flood depths might not 

survive the greater depths of the 

5-year flood, which would not 

change as much from flow reductions. The distances of upstream 

movement shown in table 22 are 

minimum estimates, because they 

are based on the factor most 

resistant to change (5-year, 14-day 

flood depth).

The estimated area of forest 

types replaced by advancing tidal 

forests was calculated from forest 

map polygon areas between the 

locations of the existing and hypothetical reach boundaries for each 

flow reduction (fig. 57). For any 

given flow reduction, the distance 

that the riverine/upper tidal boundary would move upstream is two to 

three times farther than the distance 

that the upper tidal/lower tidal 

boundary would move. The largest 

area of forest changes, however, 

would occur with the upper 

tidal/lower tidal boundary movements, because the floodplain is 

much wider at the upper tidal/lower 

tidal boundary than at the riverine/upper tidal boundaries (fig. 2).

Upstream movement of 

UTblh, replacing Rblh2/blh3, 

might occur if flows were reduced; 

however, the area of this change in 

composition was not estimated in 

this report. Differences between 

these forest types are primarily due 

to the presence of Sabal palmetto

in UTblh and its absence in 

Rblh2/blh3. Establishment of 

Sabal palmetto may be restricted 

by the upstream extent of seed dispersal by storm surges; changes in 

the upstream extent of storm surges 

that would result from flow reductions have not been quantified. In 

addition, there may be other factors 

unrelated to river flow that are 

responsible for the natural distribution limits of Sabal palmetto.

37.00 rkm

37.21 rkm

37.83 rkm

38.44 rkm

39.90 rkm

44.81 rkm

EXISTING FLOOD DEPTH

Existing boundary between

UTmix and Rblh1

Flood depth at existing boundary

between UTmix and Rblh1

-2.8 (-100)

-8.4 (-300)

-14 (-500)

-28 (-1,000)

-56 (-2000)

HYPOTHETICAL FLOW

REDUCTION —

In cubic meters per second

(cubic feet per second)

FLOOD DEPTH

33 34 35 36 37 38 39 40 41 42 43 44 45

RIVER KILOMETER

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

5-YEAR, 14-DAY FLOOD DEPTH, IN METERS

Figure 55. Estimated upstream movement of flood depth at the reach boundary between UTmix and Rblh1 forests 

if flows were reduced in the lower Suwannee River, Florida. The maximum threshold flow of the 5-year, 14-day 

flood was used to calculate the flood depth. The line showing existing flood depths by river kilometer is from the 

inset box in graph B of figure 52.
Potential Impacts of Flow Reductions 79

35

36

37

38

39

40

41

42

43

44

45

FOREST TYPE

Rblh1 (existing)

UTmix (existing)

Other forests in 10-year

floodplain

SUWANNEE RIVER

ESTIMATED NEW BOUNDARY

POSITION FOR

HYPOTHETICAL FLOW

REDUCTION–Boundary

between Rblh1 and UTmix

forests, flow reduction in cubic

meters per second (cubic feet

per second)

DISTANCE FROM RIVER

MOUTH–In kilometers

40

EXPLANATION

-28

(-1,000)

-28

(-1,000)

-14

(-500)

-8.4

(-300)

-2.8

(-100)

-56

(-2,000)

Existing boundary

between Rblh1

and UTmix

29°28′

29°29′

29°30′

29°31′

83°01′ 83°00′ 82°59′ 82°58′

0

0

0.5 1 KILOMETER

0.5 1 MILE

Manatee Springs

Figure 56. Estimated upstream movement of reach boundary between Rblh1 

and UTmix forests if flows were reduced in the lower Suwannee River, Florida. 

Distances were calculated based on changes expected in flood depths during 

the 5-year, 14-day maximum threshold flow.

Table 22. Distance that tidal forests are estimated to move upstream if flows were reduced in the lower Suwannee River, 

Florida

[Existing conditions are in black type; changes due to hypothetical flow reductions are in red type. rkm, river kilometers; m, meters; m3/s, cubic meters per 

second; ft3

/s, cubic feet per second; km, kilometers]

Existing boundary 

between forest types

New location of boundary between

forest types (based on new location

at which flood depth occurs), in rkm,

for indicated hypothetical flow

reduction, in m3

/s (ft3/s)

Distance that advancing forest type is 

predicted to move upstream and

replace retreating forest type, in km,

for indicated hypothetical flow

reduction, in m3/s (ft3 Advancing /s)

forest

type

Retreating 

forest

type

Location, 

in rkm

Flood depth 

during

5-year, 

14-day high, 

in m1

-2.8

(-100)

-8.4

(-300)

-14.0

(-500)

-28.0

(-1000)

-56.0

(-2000)

-2.8

(-100)

-8.4

(-300)

-14.0

(-500)

-28.0

(-1000)

-56.0

(-2000)

UTsw1/sw2 Rsw1/sw2 45.21 1.872 45.42 46.01 46.61 48.01 51.02 0.21 0.80 1.40 2.80 5.81

UTmix Rblh1 37.00 1.093 37.214 37.834 38.444 39.904 44.814 0.21 0.82 1.43 2.90 7.80

LTsw1/sw2 UTsw1/sw2 21.56 0.562 21.66 21.88 22.06 22.57 23.63 0.10 0.32 0.50 1.01 2.08

1

 Flood depths were calculated using the threshold discharge of the 5-year, 14-day high stage.

2

 From graph A in figure 52.

3

 From graph B in figure 52.

4

 See figure 55 for an example illustrating how these locations were calculated.

Upstream movements of 

LTmix (replacing UTmix) and 

LTham (replacing UTblh) also 

would be expected if flows were 

reduced; these estimates were not 

calculated because there were no 

stage-discharge ratings at transects 

with LTham and LTmix forests, and 

decrease in stages resulting from 

flow reductions could not be 

calculated.

Upstream Movement of Marshes 

and Salt-Tolerant Forests

The position of the tree line 

is determined primarily by salinities 

in West and East Passes. The 

boundary between forest and marsh 

would be expected to move 

upstream if flows were reduced and 

salinity increased. Regeneration 

would probably fail before canopy 

tree mortality occurred because tree 

seedlings are more sensitive to salt 

than mature trees. Relic stands 

would survive until destroyed by 

storms or by attrition of individual 

trees. These changes are already 

slowly occurring due to sea level 

rise (Williams and others, 1999), 

but changes would occur more 

quickly if salinities were increased 

as a result of flow reductions.
80 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Rsw1/sw2

Rblh1replaced by UTmix

UTsw1/sw2 replaced by LTsw1/sw2

replaced by UTsw1/sw2

0

50

100

150

200

250

300

350

400

450

0 10 20 30 40 50 60

HYPOTHETICAL FLOW REDUCTION,

IN CUBIC METERS PER SECOND

AREA OF FOREST ESTIMATED TO BE REPLACED BY

UPSTREAM MOVEMENT OF TIDAL FOREST, IN HECTARES

0 500 1,000 1,500 2,000

HYPOTHETICAL FLOW REDUCTION,

IN CUBIC FEET PER SECOND

Figure 57. Area of tidal forests estimated to move upstream if flows were reduced 

in the lower Suwannee River, Florida. Flow reductions were subtracted from 

Branford-Fort White flows.

Table 23. Distance that lower tree line is estimated to move upstream if flows were reduced in the lower Suwannee River, 

Florida 

[Existing conditions are in black type; changes due to hypothetical flow reductions are in red type. ppt, parts per thousand; rkm, river kilometers; m, meters; 

m3

/s, cubic meters per second; ft3/s, cubic feet per second]

Pass

Location of vertically averaged 5 ppt salinity at

medium flow1

, in rkm

1

 Derived from multiple linear-regression models developed by Tillis (2000) for Wilcox flow of 230 m3/s (8,120 ft3/s)

Distance that lower tree line is predicted to move 

upstream2

, in m, for indicated hypothetical flow 

reduction, in m3

/s (ft3/s)

2

 Upstream movements of salinity boundaries in Wadley and Alligator Passes were first averaged to determine movement in West Pass, then converted 

to straight-line distance, and then averaged with staight-line distances of movement in East Pass to determine average movement of lower tree line.

Under 

existing 

conditions

Under hypothetical flow reductions, in m3

/s (ft3/s)

-2.8

(-100)

-8.4

(-300)

-14.0

(-500)

-28.0

(-1000)

-56.0

(-2000)

-2.8

(-100)

-8.4

(-300)

-14.0

(-500)

-28.0

(-1000)

-56.0

(-2000)

Wadley 3.072 3.099 3.158 3.221 3.392 3.817

Alligator 2.681 2.719 2.796 2.880 3.107 3.673 32 97 166 356 811

East 1.364 1.395 1.458 1.524 1.706 2.158

Changes in location of the 

vertically averaged 5 ppt salinity at 

medium flow were calculated for 

five hypothetical flow reductions 

using multiple linear-regression 

models developed by Tillis (2000). 

These changes in location were 

converted to straight-line distances 

and averaged between West and 

East Passes to estimate the distance 

that the tree line would move 

upstream if flows were reduced 

(table 23). A hypothetical tree line 

upstream of the existing tree line 

was created on the forest map using 

the indicated distance for each flow 

reduction. Figure 58 shows estimated movement of the tree line for 

a flow reduction of 28 m3

/s 

(1,000 ft3

/s). The total area of forests that are regularly inundated by 

tides (LTsw1, LTsw2, and LTmix) 

lying between the existing and 

hypothetical tree lines was determined for each flow reduction 

(fig. 59). Marshes, open water, 

aquatic beds, and hammocks 

located between existing and hypothetical tree lines were excluded 

from the areas plotted in figure 59 
Potential Impacts of Flow Reductions 81

because these features are either 

already marshes or would not convert to marshes if salinities 

increased. Forests near the southeastern edge of the study area also 

were excluded because these areas 

are isolated from salinity changes 

in East Pass.

Suwannee River

West Pass

East Pass

River

Gopher

LAND COVER

Open water

LTsw1/sw2 and LTmix (includes altered)

LTham (includes altered)

Emergent aquatic beds

Marshes

LT FOREST ESTIMATED TO BE

REPLACED BY MARSH

EXISTING TREE LINE

EXPLANATION

Suwannee

0

0

0.5 1 KILOMETER

0.5 1 MILE

29°18′

29°19′

83°09′ 83°08′ 83°07′ 83°06′ 83°05′

29°15′

29°30′

83°15′ 83°00′ 82°45′

Old Town

DIXIE

LEVY

GILCHRIST

Chiefland

Fanning

Springs

Suwannee

Gulf

of

Mexico

27

ALT Suwannee River

4 8 MILES

0 8 KILOMETERS

27

ALT

98

19

19

98

0

4

INSET MAP

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 58. Area of lower tidal forests estimated to convert to marsh if flows were reduced 28 cubic meters per second 

(1,000 cubic feet per second) in the lower Suwannee River, Florida. This hypothetical flow reduction was subtracted from 

flow at the Wilcox gage.

Throughout most of the 

lower tidal reach upstream of the 

tree line, LTsw1/sw2, LTmix, and 

LTham forests would be expected 

to change in composition if flows 

were reduced because conditions 

would favor more salt-tolerant 

species. However, the area of these 

changes was not estimated because 

flow reductions would result in a 

change in composition without a 

change in forest type, and these 

changes would result from salinity 

increases that could not be quantified. Storm surge from a very large 

hurricane making landfall in this 
82 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

area could cover forests with saline 

water throughout the lower tidal 

reach (and possibly in the downstream part of the upper tidal 

reach). The height of a storm surge 

is highly variable depending upon 

the intensity, path, speed of forward 

motion, and other characteristics of 

the storm (Ho and Tracey, 1975). 

However, if river flows were lower 

than normal due to flow reductions 

at the time a storm made landfall, 

water from the storm surge covering the forests throughout this area 

would be more saline than normal, 

and salt concentrations in the soils 

would increase. Some species with 

downstream limits in the lower tidal 

reach, such as Nyssa aquatica, may 

be very sensitive to slight increases 

in salinity. Diversity of lower tidal 

forests would decrease if the most 

salt-intolerant species were elimi0

100

200

300

400

500

600

700

0 10 20 30 40 50 60

HYPOTHETICAL FLOW REDUCTION,

IN CUBIC METERS PER SECOND

AREA OF LTsw1, LTsw2, AND LTmix FORESTS

ESTIMATED TO CONVERT TO MARSH,

IN HECTARES

0 500 1,000 1,500 2,000

HYPOTHETICAL FLOW REDUCTION,

IN CUBIC FEET PER SECOND

Figure 59. Area of lower tidal forests estimated to convert to marsh if flows were 

reduced in the lower Suwannee River, Florida. Flow reductions were subtracted 

from Branford-Fort White flows.

nated. Elevated salinities in the 

lower tidal reach also could alter 

plant composition in marshes 

occurring both upstream and downstream of the tree line, changing 

some areas from freshwater to 

brackish marshes, and others from 

brackish to saltwater marshes 

(Clewell and others, 1999).

Summary of Forest Composition 

Changes

In the lower Suwannee River 

floodplain, 13 different kinds of wetland forest composition changes 

would be expected to occur if flows 

were reduced (table 24). Total areas 

of forests expected to change to 

marsh or another forest type range 

from 159 ha (1.1 percent of the total 

area) for a permanent long-term 

flow reduction of 2.8 m3

/s 

(100 ft3

/s), to 2,464 ha (17.6 percent) 

for a flow reduction of 56 m3

/s 

(2,000 ft3

/s). The total area of wetland forests in the lower Suwannee 

floodplain is about 14,000 ha.

Totals and subtotals of wetland forest changes shown at the 

bottom of table 24 represent the 

minimum change expected if flows 

were reduced, for the following reasons. (1) Totals do not include 

areas impacted by specific changes 

8, 10, 11, and 13 that are expected 

to occur, but could not be estimated. (2) Calculations for specific 

changes 1, 2, 4, 6, 7, and 9 were 

based on the hydrologic factor that 

was most resistant to change 

(5-year, 14-day flood depths). 

These forest types are also affected 

by other important hydrologic factors, such as duration of inundation, 

duration of saturation, and 2-year, 

14-day flood depths, which would 

change more than 5-year, 14-day 

flood depths, as shown in the example in table 20. (3) It is likely that 

all forests in all reaches would be 

altered to some degree by flow 

reductions, but not all areas would 

change enough to be classified as a 

different forest type. Areas of forest 

changes in table 24 do not include 

areas that would change in composition but would not change to 

another forest type.

Loss of Inundated and 

Saturated Area in 

Floodplain Forests

Inundated area in riverine 

forests is very limited at the lowest 

flows (fig. 47). Loss of inundated 

areas resulting from flow reductions at low flow could further 

decrease aquatic habitats for floodplain animals at a time when those 

habitats are already scarce. Loss of 

inundated area for five hypothetical 
Potential Impacts of Flow Reductions 83

Table 24. Summary of wetland forest composition changes expected to occur if flows were reduced in the lower Suwannee 

River, Florida

[For these estimates, the assumption was made that flow reductions would cause existing forest types to change to different existing types (with drier, more 

tidal, or more salt-tolerant species). However, hydrologic changes, particularly if they are large and rapidly occurring, could provide opportunities for exotic 

species to invade or could alter the mix of native species so that the new forest composition is different from any existing type. m3

/s, cubic meters per 

second; ft3

/s, cubic feet per second]

General change Specific change (existing forest types expected to 

change are indicated by bold type)

Total 

area of 

forest 

types, in 

hectares

Area of forest types, in hectares

or percent (%), estimated to change with 

indicated flow reduction, in m3

/s (ft3/s)

-2.8

(-100)

-8.4

(-300)

-14.0

(-500)

-28.0

(-1000)

-56.0

(-2000)

Change to drier 

forest type

due to decreased 

flood depths and 

duration of 

inundation and 

saturation

1. Rsw1/sw2 becomes drier and partially shifts to Rblh1 1,735 20

1.2%

65

3.8%

104

6.0%

211

12.1%

430

24.8%

2. Rblh1 becomes drier and partially shifts to Rblh2/blh3 1,273 11

0.8%

36

2.8%

59

4.6%

118

9.3%

241

18.9%

3. Rblh2/blh3 becomes drier and partially shifts to upland 2,031 12

0.6%

40

1.9%

64

3.2%

130

6.4%

264

13.0%

4. UTmix becomes drier and partially shifts to UTblh 403 5

1.3%

18

4.4%

30

7.5%

58

14.5%

117

28.9%

5. UTblh becomes drier and partially shifts to upland 797 4

0.5%

13

1.7%

23

2.9%

44

5.5%

88

11.0%

Upstream

movement of 

tidal forest 

due to decreased 

flood depths

6. UTsw1/sw2 moves upstream, replacing the most 

downstream forests of Rsw1/sw2 1,735 90.5%

37

2.1%

69

4.0%

130

7.5%

175

10.1%

7. UTmix moves upstream, replacing the most downstream 

forests of Rblh1 1,273 60.5%

20

1.5%

29

2.3%

58

4.6%

197

15.4%

8. UTblh moves upstream, replacing the most downstream 

forests of Rblh2/blh3 2,031 Estimates not available

9. LTsw1/sw2 moves upstream, replacing the most 

downstream forests of UTsw1/sw2 2,092 211.0%

77

3.7%

129

6.2%

248

11.8%

416

19.9%

10. LTmix moves upstream, replacing the most downstream 

forests of UTmix 403 Estimates not available

11. LTham moves upstream, replacing the most downstream 

forests of UTblh 797 Estimates not available

Upstream movement of marsh 

or salt-tolerant 

forest due to 

increased salinity

12. Marsh moves upstream, replacing LTsw/sw2 and LTmix

along lower tree line 3,873 721.9%

168

4.3%

238

6.2%

376

9.7%

618

16.0%

13. LTsw1/sw2, LTmix, and LTham change in composition 

toward more salt-tolerant species 5,662 Estimates not available

Area of Rsw1/sw2 changed by both nos. 1 and 6 (duplication subtracted from subtotals) -0.1 -1.4 -4.1 -15.8 -43.3

Area of Rblh1 changed by both nos. 2 and 7 (duplication subtracted from subtotals) -0.1 -0.6 -1.3 -5.4 -37.1

 SUBTOTAL RIVERINE1 5,039 58

1.2%

196

3.9%

320

6.3%

625

12.4%

1,225

24.3%

SUBTOTAL UPPER TIDAL1 3,293 29

0.9%

108

3.3%

182

5.5%

350

10.6%

620

18.8%

SUBTOTAL LOWER TIDAL1 5,662 72

1.3%

168

3.0%

238

4.2%

376

6.6%

618

10.9%

 TOTAL1 13,994 159

1.1%

471

3.4%

740

5.3%

1,351

9.7%

2,464

17.6%

1

Because quantitative estimates were not available for some forest types, totals and subtotals of areas estimated to change do not include all of the wetland forest areas that would be expected to change if flows were reduced.
84 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

flow reductions, ranging from 2.8 

to 56 m3

/s (100-2,000 ft3/s), are 

shown in percent (fig. 60) and in 

hectares (table 25) in relation to the 

river flow at which the reduction 

occurs.

HYPOTHETICAL FLOW

REDUCTION-In cubic

meters per second

(cubic feet per second)

-56 (-2,000)

-56 (-2,000)

-28 (-1,000)

-14 (-500)

-8.4 (-300)

-2.8 (-100)

0 100 200 300 400 500 600 700 800 Median Flo

w

2-year, 1-day High Flo

w

0

10

20

30

40

50

60

70

80

90

100

ESTIMATED LOSS OF INUNDATED AREA

IN RIVERINE FORESTS, IN PERCENT OF

TOTAL AVAILABLE UNDER EXISTING CONDITIONS

FLOW, IN CUBIC METERS PER SECOND

FLOW, IN CUBIC FEET PER SECOND

0 10,000 15,000 20,000 25,000 5,000

Figure 60. Percent loss of inundated area in floodplain forests of the riverine reach of the lower Suwannee River, 

Florida, estimated for five hypothetical flow reductions in relation to flow at which reduction occurs. Flow is 

combined flow of Suwannee River at Branford and Santa Fe River near Fort White. Median and 2-year, 1-day high 

flows are based on 1933-99 records.

Table 25. Estimated loss of inundated area in riverine forests for five hypothetical flow reductions, in relation to selected 

flows in the lower Suwannee River, Florida

[Existing conditions are in black type; changes due to hypothetical flow reductions are in red type. m3/s, cubic meters per second, ft3/s, cubic feet per 

second; %, percent] 

Existing conditions Loss of inundated area, in hectares,

for indicated hypothetical flow reduction,

in m3

/s (ft3 Flow Duration flow /s)

is equalled 

or exceeded

 (1933-99)

Inundated

area, 

m in hectares 3

/s ft3/s -2.8

(-100)

-8.4

(-300)

-14.0

(-500)

-28.0

(-1000)

-56.0

(-2000)

61.7 2,200 100% 17.4 4.2 12.5 16.8 17.4 17.4

83.7 2,990 95% 78.0 10.1 29.8 44.6 70.2 78.0

120 4,300 75% 310 21.8 66.3 105 189 289

181 6,480 50% 808 21.4 63.0 108 223 449

297 10,600 25% 1620 20.3 63.5 102 200 397

608 21,700 5% 3927 18.1 53.9 90.7 188 389

All flow reductions show a 

greater percent loss of inundated 

area at low flows than at high flows 

(fig. 60). For a reduction of 2.8 m3

/s 

(100 ft3

/s) occurring above median 

flow, loss of inundated area is proportionally small (less than 

5 percent). As flows decrease 

below the median flow, however, 

the impact becomes greater. At the 

lowest flow in the period of record 

(61.7 m3

/s, 2,200 ft3/s), inundated 
Potential Impacts of Flow Reductions 85

area in riverine forests is scarce at 

17.4 ha (table 25). The loss of 

4.2 ha from the remaining 17.4 ha 

with a flow reduction of 2.8 m3

/s 

(100 ft3

/s) represents a 24 percent 

loss of inundated area, and nearly 

all inundated area (95 percent) is 

lost with a flow reduction of 

14 m3

/s (500 ft3/s). 

If large flow reductions 

occurred during high flows, the 

result could be a substantial loss of 

aquatic habitat for main channel 

fishes and a decrease in the amount 

of nutrients and detritus transported 

from the floodplain to the river and 

estuary. Losses in the 283-425 m3

/s 

(10,000-15,000 ft3

/s) flow range are 

estimated to be as much as 15 percent with a 28 m3

/s (1,000 ft3/s) 

reduction, and as much as 30 percent with a 56 m3

/s (2,000 ft3/s) 

reduction (fig. 60). Losses of 

HYPOTHETICAL FLOW

REDUCTION-In cubic

meters per second

(cubic feet per second)

-56 (-2,000)

-56 (-2,000) -8.4 (-300)

-14 (-500)

-2.8 (-100)

-28 (-1,000)

0 100 200 300 400 500 600 700 800 Median Flo

w

2-year, 1-day High Flo

w

0

10

20

30

40

50

60

70

80

90

100

ESTIMATED LOSS OF SATURATED AREA

IN RIVERINE FORESTS, IN PERCENT OF

TOTAL AVAILABLE UNDER EXISTING CONDITIONS

FLOW, IN CUBIC METERS PER SECOND

FLOW, IN CUBIC FEET PER SECOND

0 10,000 15,000 20,000 25,000 5,000

Figure 61. Percent loss of saturated area in floodplain forests of the riverine reach of the lower Suwannee River, 

Florida, estimated for five hypothetical flow reductions in relation to flow at which reduction occurs. Saturated area 

includes inundated area. Flow is combined flow of Suwannee River at Branford and Santa Fe River near Fort 

White. Median and 2-year, 1-day high flows are based on 1933-99 records.

inundated area resulting from flow 

reductions were calculated in this 

study for the riverine reach only. In 

the upper tidal reach, the relation of 

inundated area in the floodplain to 

river flow is poor during low flows, 

but good during high flows. Thus, 

at high flows, the percentage losses 

of inundated area from flow reductions in the upper tidal reach are 

probably similar to those in the riverine reach.

The amount of saturated area 

in riverine forests decreases in 

response to decreasing river flows 

(fig. 48). Loss of saturated area for 

five hypothetical flow reductions, 

ranging from 2.8 to 56 m3

/s (100-

2,000 ft3

/s), are shown in percent 

(fig. 61) and in hectares (table 26) 

in relation to the river flow at which 

the reduction occurs.

At low flow, there is more 

saturated area than inundated area 

in the floodplain. At the lowest 

recorded river flow (61.7 m3

/s, 

2,200 ft3

/s), an estimated 624 ha of 

saturated area exist in riverine forests, compared to 17.4 ha of inundated area. For all flow reductions 

occurring below the median flow of 

181 m3

/s (6,480 ft3/s), loss of saturated area is much greater than loss 

of inundated area (tables 26 and 25, 

respectively). At the lowest 

recorded flow, for example, flow 

reductions ranging from 2.8 to 

56 m3

/s (100-2,000 ft3/s), result in 

losses of 21.2 to 624 ha of saturated 

area compared to losses of only 4.2 

to 17.4 ha of inundated area. The 

trend showing greater percentage 

losses at lower flows is similar for 

both (figs. 60 and 61); however, 

percent loss of saturated area is less 

than percent loss of inundated area.
86 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Loss of saturated area resulting from flow reductions at low 

flow could result in an increase in 

oxidation of organic soils in the 

riverine reach. Calculations presented in figure 61 and table 26 

include estimated losses of saturated area as a direct result of flow 

reductions, but do not include additional losses of saturated area that 

would result indirectly from 

decreases in water-holding capacity if organic soils were lost to oxidation. Organic soils have a much 

higher water-holding capacity than 

mineral soils (Buckman and Brady, 

1969), therefore these additional 

losses of saturated area resulting 

from loss of organic matter could 

be quite large. 

Ecological Consequences 

of Flow Reductions

Wetlands in a forested floodplain have many different physical, chemical, and biological 

functions that are dependent upon 

the fluctuating hydrologic regime 

of the river (Greeson and others, 

eds., 1979; Brinson and others, 

1981; Wharton and others, 1982; 

Gosselink and others, eds.,1990; 

Lugo and others, eds., 1990; Davis 

and others, 1996; Messina and 

Conner, eds., 1998; Mitsch and 

Gosselink, 2000). If flows were 

reduced in the lower Suwannee 

River, the ecological consequences 

occurring in its forested floodplain 

would be diverse and numerous 

(table 27). 

Hydrologic changes could 

increase the possibility of invasion 

by exotic plants. If floodplain forests in the lower Suwannee River 

become drier or more saline, they 

could be vulnerable to invasion by 

Sapium sebiferum, Chinese tallow 

tree. This species has a relatively 

high tolerance for extremes of 

flooding and drying, saturated 

soils, shade, and saline conditions 

(Conner and Askew, 1993; Langeland and Burks, eds., 1998; K. 

Burke, Florida Department of 

Environmental Protection, written 

commun., 2000). Although not 

observed in the lower Suwannee 

River floodplain, Sapium sebiferum

has invaded other floodplains in the 

southeastern coastal plain and has 

the potential to become a serious 

pest species (Conner and Askew, 

1993). Lygodium japonicum, 

Japanese climbing fern, is present 

in the lower Suwannee floodplain, 

and could increase in abundance if 

forests become drier. This species, 

which is tolerant of hydrologically 

extreme conditions, has been 

observed to form tangled masses 

covering shrubs and ground-cover 

vegetation of other floodplain 

forests, smothering seedlings of 

potential overstory tree species 

(Langeland and Burks, eds., 1998). 

Lygodium japonicum and other 

exotic ground-cover species in 

Apalachicola River floodplain forests were much more dense in the 

hydrologically altered forests of the 

upper reach than in other reaches 

(Light and Darst, 1997; Light and 

others, 1998). A number of exotic 

shrubs and other ground-cover species are present in the lower 

Suwannee River floodplain in 

small numbers, and some of these 

could become more abundant if 

flows were reduced.

Table 26. Estimated loss of saturated area in riverine forests for five hypothetical flow reductions, in relation to selected 

flows in the lower Suwannee River, Florida

[Existing conditions are in black type; changes due to hypothetical flow reductions are in red type. Saturated area includes inundated area. m3/s, 

cubic meters per second, ft3

/s, cubic feet per second; %, percent] 

Existing conditions Loss of saturated area, in hectares,

for indicated hypothetical flow reduction,

in m3

/s (ft3/s) Flow Duration flow 

is equalled 

or exceeded

 (1933-99)

Saturated

area, 

in hectares m3

/s ft3/s -2.8

(-100)

-8.4

(-300)

-14.0

(-500)

-28.0

(-1000)

-56.0

(-2000)

61.7 2,200 100% 624 21.2 63.5 103 191 624

83.7 2,990 95% 788 23.1 69.0 112 212 621

120 4,300 75% 1212 27.0 80.6 132 256 602

181 6,480 50% 1817 25.7 76.8 126 253 494

297 10,600 25% 2337 16.6 49.6 82.1 168 309

608 21,700 5% 4030 10.6 31.8 52.9 108 248
Potential Impacts of Flow Reductions 87

Table 27. Potential ecological consequences of flow reductions on the forested floodplain of the lower Suwannee River, Florida

Type of 

impact Potential ecological consequence

Wetland forest types affected

 Rsw1/sw2 Rblh1 Rblh2/blh3 UTsw1/sw2 UTmix UTblh LTsw1/sw2 LTmix LTham

Change in 

forest 

composition

Increased possibility of invasion by exotic plants X X X X X X X X X

Decrease in biological diversity due to loss of vertical structure and 

woody micro-habitats in forests converted to marshes X X

Increased vulnerability to human disturbance X X

Decrease in canopy basal area, canopy species richness, and preferred 

wildlife habitat due to loss of wetlands X X

Decrease in area of wettest swamps and important swamp species such 

as Taxodium distichum and Nyssa aquatica X

Decrease in wildlife value due to conditions favoring opportunistic 

instead of mast-producing bottomland hardwood species X X

Loss of 

saturated 

areas

Decrease in nitrate removal by denitrification due to drier (more oxygenated) conditions X X X

Decrease in water retention in soils during dry periods due to loss of 

organic soils from oxidation X

Increased vulnerability to fire due to dessicated soils X X X

Loss of 

inundated 

areas

At low 

flows

Decrease in aquatic habitat that is critical to survival of 

floodplain-dependent fishes and aquatic invertebrates X

Decrease in aquatic habitat that is important to birds, reptiles, 

amphibians, and mammals that use floodplain ponds X

At high 

flows

Decrease in aquatic habitat in the floodplain that is important to 

main channel fishes for food, shelter, and reproduction X X X X X X

Decrease in transport of nutrients and detritus out of floodplain 

forests and into the river and estuary X X X X X X

One of the greatest impacts 

of flow reductions on floodplain 

forests would be the loss of forests 

to marshes at the tree line (change 

12 in table 24). Loss of forests at 

the tree line is already occurring 

due to sea level rise; however, 

increased salinity due to flow 

reductions would accelerate this 

process. Although marshes are productive wetland habitats, the 

amount of complex structural diversity provided by forested wetlands 

would decrease. The vertical structure of the forest not only allows for 

leaf production at various layers 

above ground level, it also provides 

substrates for a diverse assortment 

of epiphytes such as lichens, 

mosses, liverworts, ferns, orchids, 

and bromeliads. In addition, the 

vertical structural diversity of forests offers greater opportunities for 

wildlife, such as birds, lizards, 

snakes, and squirrels, to forage, 

nest, and escape from predators 

(Wigley and Lancia, 1998). Wetland forests have numerous microhabitats, such as tree cavities, 

standing dead snags, fallen logs, 

small woody debris, cypress knees, 

root mats, and shaded pools, which 

are important to animals but do not 

exist in marshes.

Changes 3 and 5 in the 

riverine and upper tidal reaches 

(table 24) would also result in an 

overall loss of forested wetlands 

due to conversion to uplands. 

Probably the most important 

consequence of this impact would 

be the increased vulnerability of 

these drier areas to human disturbance. Upland forests in the lower 

Suwannee River floodplain are far 

more likely to be altered for agricultural or residential use than bottomland hardwood forests (figs. 24 

and 26). As a result of increased 

disturbance or drier conditions (or 

both), degradation of certain forest 

characteristics could occur if wetlands were converted to upland forests. Basal area of canopy trees in 

upland forests in this study was the 

lowest of all 14 forest types in the 

10-year floodplain (fig. 40). Species richness of the canopy and subcanopy of upland forests was lower 

than riverine bottomland hardwood 
88 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

forests (fig. 39). Other studies indicate that floodplain wetlands are 

more productive areas for wildlife 

than uplands because of the abundance of wildlife foods and diversity of habitats (Schitoskey and 

Linder, 1979; Brinson and others, 

1981).

Flow reductions are expected 

to have a greater impact on riverine 

swamps (changes 1 and 6 in 

table 24) than on most other forest 

types. Invasion of bottomland 

hardwood or tidal species could, 

over the long term, reduce the abundance of Taxodium distichum, an 

important swamp species that is 

exceptional with regard to its longevity. Individuals of this species 

have the potential to live 

1,000 years or more (Mattoon, 

1915), providing massive oldgrowth trees with an abundance of 

tree cavities that provide valuable 

habitats for many species of birds. 

As a result of commercial exploitation of cypress in the last 120 years, 

the floodplain forest that exists 

today provides little evidence of the 

splendor of an old-growth cypress 

swamp. In 1774, William Bartram 

described dugout canoes made 

from cypress trees near Manatee 

Springs that carried 20 or 30 Native 

Americans in each canoe and made 

regular trading excursions to Cuba 

and back (Harper, ed., 1958). If riverine swamps could be protected 

from flow reductions and other 

threats, the extensive public land 

acquisitions that have occurred in 

recent years could allow for the 

return of old-growth cypress stands 

on the Suwannee River.

Nyssa aquatica, another 

important swamp species, requires 

wet conditions to thrive in the seedling stage (Applequist, 1959; 

Dickson and others, 1965). If flows 

were reduced, regeneration of this 

species would be restricted by 

decreases in soil saturation as well 

as competition from bottomland 

hardwoods. Nyssa aquatica is also 

sensitive to low levels of salinity, 

and distribution of this species on 

the Suwannee River floodplain may 

be further limited in tidal reaches 

by increases in salinity. 

If riverine swamps were 

hydrologically altered and became 

drier, opportunistic bottomland 

hardwood species such as Liquidambar styraciflua, Betula nigra, 

and Acer rubrum might be the first 

to invade and could persist indefinitely. Although some of these 

altered forests would no longer be 

swamps, they might not have the 

same composition as existing 

stands of low bottomland hardwoods either. Increased competition from opportunistic species 

might result in lower production of 

mast (acorns and nuts) by Quercus 

laurifolia, Quercus lyrata, and 

Carya aquatic. Mast is an important food for birds and other floodplain wildlife (Frederickson, 1978). 

In addition, if low bottomland hardwoods became drier and converted 

to high bottomland hardwoods, species such as Quercus lyrata and 

Carya aquatica would decrease in 

abundance because, as low bottomland hardwood species, they would 

not able to compete in drier communities (table 14 in present study; 

Larson and others, 1981; Wharton 

and others, 1982).

The ability of wetlands to 

improve water quality may be one 

of the most important reasons for 

wetlands protection (Mitsch and 

Gosselink, 2000). Increasing nitrate 

concentrations detected in Suwannee River water in recent years have 

raised water-quality concerns in the 

basin (Katz and others, 1997; 

Hornsby and Mattson, 1998). If 

floodplain soils become less saturated as a result of flow reductions, 

the ability of riverine forests to 

remove nitrates from river water 

may be diminished. Nitrates can be 

removed by denitrification, a 

microbial process that requires 

organic matter and takes place in 

the absence of oxygen near the aerobic-anaerobic interface (Brinson 

and others, 1981; Brinson and others, 1984; Kovacic and others, 

1990; Davis and others, 1996). 

Adequate amounts of organic matter exist at the surface of floodplain 

soils, but if flow reductions 

decreased the amount of saturated 

areas, the resulting decrease in 

anaerobic conditions would limit 

the denitrification process. Flow 

reductions could also affect many 

other chemical transformations in 

wetland soils that require anaerobic conditions and may contribute 

to water-quality enhancement. 

When soils become waterlogged, 

oxygen depletion is followed by 

nitrate and sulfate reduction, and 

increases in reduced manganese, 

reduced iron, hydrogen sulfide, 

methane, available ammonium, and 

phosphate ions (Mitsch and 

Gosselink, 2000). 

Oxidation of organic matter 

due to decreased saturation and 

anaerobiosis may diminish the ability of organic soils in riverine 

swamps to retain water during dry 

periods. Organic soils have a much 

higher water-holding capacity than 

mineral soils, and serve as a sponge 

to retain water in floodplain soils 

long after the flood season ends, 

mitigating the effects of dry periods. If flows are reduced and 

organic matter is oxidized, loss of 

water-retention ability would accelerate the drying time of riverine 

swamp soils, and could increase the 

frequency and duration of droughty 

conditions in the floodplain. 

Drier forests and desiccated 

soils resulting from flow reductions 
Potential Impacts of Flow Reductions 89

could increase vulnerability of the 

floodplain to fire in the riverine 

reach. Although floodplain fires are 

rare, they can occur if conditions 

are dry and adjacent upland forests 

are burning. Riverine swamps are 

commonly found at the floodplainupland boundary. Under normal 

conditions, these wet swamps serve 

as an effective firebreak protecting 

the drier bottomland hardwood forests that are closer to the river. If 

the swamps dry sufficiently to carry 

a fire, susceptibility to fire will 

increase for all areas of the floodplain. Fires can be particularly 

harmful in the floodplain because 

floodplain forests are not fireadapted communities. If reduced 

flows and drier than normal conditions continue after a fire, recovery 

may be slow. Fires could result in 

long-term changes in tree species 

composition, and can destroy 

organic soils that may not be 

replenished for several centuries 

(Cohen and others, 1984).

If flow reductions occurred at 

low flows, the resulting decreases 

in the amount of inundated area in 

riverine swamps could impact not 

only forest composition but also a 

variety of floodplain animals 

(Fredrickson, 1979; Conner and 

Buford, 1998; Meyer, 1998; Wigley 

and Lancia, 1998). Small areas of 

standing water in the forest during 

low-flow periods serve as watering 

holes and foraging sites for floodplain mammals such as otters, beavers, raccoons, deer, bobcats, and 

rabbits. Birds that nest or roost in 

swamps with standing water 

include the swallow-tail kite, prothonotary warbler, hooded merganser, and wood duck, as well as 

colony nesters such as yellowcrowned night heron, green heron, 

great blue heron, great egret, white 

ibis, and wood storks. Areas of 

standing water in the forest are also 

important to reptiles such as alligators, several species of snakes, and 

a variety of amphibians including 

sirens, amphiumas, salamanders, 

toads, and frogs.

Of all the floodplain animals, 

aquatic invertebrates and fishes are 

the most dependent upon areas of 

standing water in swamps. Aquatic 

invertebrate communities in these 

habitats include macroinvertebrates such as crayfish, clams, oligochaete worms, snails, freshwater 

shrimp, midges, amphipods, and 

various immature insects; and 

microinvertebrates such as rotifers, 

copepods, nematodes, and ostracods (Clark, 1979; Sniffen, 1981; 

Wharton and others, 1982; Mitsch 

and Gosselink, 2000). Floodplaindependent fishes include flier, 

pirate perch, mosquitofish, warmouth, taillight shiner, bluegill, 

banded pygmy sunfish, bluespotted 

sunfish, and redfin pickerel (Wharton and others, 1982; Leitman and 

others, 1991). 

If flows were reduced, floodplain-dependent animals would be 

affected not only by decreased 

inundated area, but also by 

increased frequency of droughts 

that severely reduce or eliminate 

aquatic habitats in the floodplain; 

however, drought frequencies were 

not addressed in this report. Additional research is needed on the 

increased frequency of low-flow 

events that would result from flow 

reductions.

During high flows, aquatic 

habitats in the floodplain provide 

increased food, shelter, spawning 

sites, and nursery grounds for main 

channel fishes. Studies indicate that 

most fish species in southeastern 

rivers utilize floodplain habitats 

during floods (Wharton and others, 

1982; Baker and others, 1991; Leitman and others, 1991; Hoover and 

Killgore, 1998). When inundated 

by high water, the floodplain provides abundant food supplies for 

main channel fishes. Terrestrial 

invertebrates in leaf litter, woody 

debris, and live vegetation, as well 

as aquatic invertebrates in shallow, 

isolated pools in the forest all 

become available to fishes when the 

floodplain is inundated and connected to the main river channel 

during flooding. The abundance of 

vegetative cover in flooded forests 

has been shown to be important for 

nesting sites, as well as for survival 

of young fishes (Welcomme, 1979; 

Savino and Stein, 1982; Benke and 

others, 1985; Harmon and others, 

1986).

Losses of inundated area 

would be substantial if large flow 

reductions occurred during high 

flows ranging from 283 to 425 m3

/s 

(10,000-15,000 ft3

/s) (fig. 60). 

These reductions in fish habitat sustained over time could decrease 

diversity and productivity of 

Suwannee River fishes. Abundance 

of fishes is related to timing and 

extent of floodplain inundation 

(Guillory, 1979; Wharton and others, 1982; Ross and Baker, 1983; 

Killgore and Baker, 1996); declines 

in diversity and abundance of some 

species have been linked to reductions in aquatic habitat in the floodplain (Hoover and Killgore, 1998).

Transport of organic material out of riverine and upper tidal 

forests and into the river and estuary could also be affected by large 

flow reductions occurring in the 

283-425 m3

/s (10,000-15,000 ft3/s) 

flow range. Water is moving 

through the floodplain at and above 

these flows (fig. 47). Large flow 

reductions at these flows could significantly decrease the amount of 

flowing water in the floodplain, 
90 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

which could reduce the amount and 

alter the timing of nutrient and 

detritus exported from wetland forests. Many aquatic organisms in 

rivers and estuaries that depend 

upon particulate organic detritus 

and other floodplain exports as food 

sources could be adversely affected 

by flow reductions (Livingston and 

others, 1974; Brinson and others, 

1981; Mitsch and Gosselink, 2000).

SUMMARY 

A study relating hydrologic 

conditions, soils, and vegetation of 

floodplain forests to river flow in 

the lower Suwannee River, Florida, 

was conducted from August 1996 

to September 2000. The study was 

done by the U.S. Geological Survey 

in cooperation with the Suwannee 

River Water Management District 

to help determine the minimum 

flows and levels required for wetlands protection.

The Suwannee River is the 

second largest river in Florida in 

terms of average discharge. The 

study area is the 10-year 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. 

The study area includes about 

18,600 ha that are presently or were 

historically forested, 75 percent of 

which is wetlands and 25 percent is 

uplands. Approximately 29 percent 

of the 10-year floodplain has been 

altered for agricultural or residential use, with most of the altered 

areas in the uplands.

The study area is divided into 

riverine, upper tidal, and lower tidal 

reaches because hydrologic conditions, vegetation, and soils in the 

floodplain change with distance 

from the river mouth. River kilometers (rkm) are used to indicate 

stream distances starting with rkm 

0 at the mouth of the river and 

extending to rkm 106 at the confluence of the Suwannee and Santa Fe 

Rivers.

Median flow, based on 

combined flow of the Suwannee 

River at Branford and the Santa Fe 

River near Fort White from 1933-

99, was approximately 181 m3

/s 

(6,480 ft3

/s), with typical annual 

flows ranging from the median 

annual 1-day low flow of 101 m3

/s 

(3,600 ft3

/s) to the median annual 

1-day high flow of 571 m3

/s 

(20,400 ft3

/s). At the upstream 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 flows in the lower 

tidal reach. Median tidal range at 

the mouth of the Suwannee River is 

about 1 m. In the downstream part 

of the lower tidal reach, stages during storm surges are higher than 

river flood stages; however, the 

duration of storm surges is usually 

less than 24 hours.

Salinity of river water in the 

lower tidal reach decreases with 

increasing flow and with increasing 

distance from the mouth. During 

low flow, measured salinities range 

from 20-30 ppt in Suwannee Sound 

to 0.5 ppt near the mouth of the 

Gopher River at rkm 9.1. Salinity of 

river water can be much higher during storm surges that occur during 

low-flow periods.

Salinity of surface waters in 

some isolated forests of the lower 

tidal floodplain is higher than salinity in the main river channel 

because saline water periodically 

deposited by storm surges is 

trapped in ponds that are not 

flushed by tides. The highest water 

salinity measured in the floodplain 

during this study (5.2 ppt) was 

found in an isolated swamp near the 

tree line in February 1997, about 

4 months after Hurricane 

Josephine.

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 the lower tidal transects.

Seven soil orders and 18 taxonomic subgroups are found in the 

study area with the most common 

orders being Entisols and Histosols. 

Soils in all riverine forests except 

Rsw1 are predominantly mineral 

(sand, loam, or clay) and are dry 

during low-flow periods. Soils in 

Rsw1, upper tidal, and lower tidal 

forests are predominantly organic 

on the surface, with organic or mineral subsurface textures. Most surface soils in Rsw1 forests, upper 

and lower tidal swamps, and lower 

tidal mixed forests were continuously saturated during the data collection period. The electrical 

conductivity of surface soils in the 

downstream part of the lower tidal 

reach is high enough (greater than 

4 mmhos/cm) to exclude many tree 

species that are intolerant of salinity. Surface soils in some isolated 

forests have considerably higher 

conductivities than soils in forests 

receiving regular tidal inundation. 

The highest soil conductivity 

measured in the study area was 

13.7 mmhos/cm in surface soils of 

an isolated forest near the tree line.

A total of 77 tree, shrub, and 

woody vine species were identified 

in the canopy and subcanopy of 

floodplain wetland forests 

(n = 8,376). Species richness in the 

lower Suwannee River floodplain is 

high compared to other river 

floodplains in North America. Taxodium distichum is the most impor-
Summary 91

tant canopy tree species by basal 

area in wetland forests of riverine 

and tidal reaches of the floodplain. 

One upland forest type and 13 wetland forest types were defined from 

vegetative sampling and mapped 

using digitized aerial photographs: 

• Oak/pine upland forests 

(oak/pine) are found in both 

the riverine and upper tidal 

reaches, and have the lowest 

basal area of canopy trees 

(21 m2

/ha) of all forests of the 

floodplain. Quercus 

hemisphaerica is the most 

important canopy species by 

basal area.

• Riverine high bottomland 

hardwoods (Rblh2 and Rblh3) 

have higher canopy species 

richness (40-42 species) than 

all other forest types in the 

floodplain. Quercus virginiana is the most important canopy tree by basal area. 

Riverine low bottomland hardwoods (Rblh1) are dominated 

by five species in the canopy 

with Quercus laurifolia the 

most important by basal area. 

Riverine swamps (Rsw1 and 

Rsw2) are found in the lowest 

and wettest areas with Taxodium distichum the most 

important canopy species by 

basal area.

• Upper tidal bottomland hardwoods (UTblh) are differentiated from riverine forests by 

the presence of Sabal palmetto

in the canopy. Upper tidal 

mixed forests (UTmix) and 

upper tidal swamps (UTsw1 

and UTsw2) are differentiated 

from riverine forests, in part, 

by the presence of Fraxinus 

profunda in the canopy. Nyssa 

aquatica, the most important 

canopy species by basal area in 

upper tidal swamps, is absent 

from most forests in the lower 

tidal reach where its distribution is probably restricted by 

salinity.

• Lower tidal hammocks 

(LTham) are hydric hammocks, a unique wetland type 

that is rare outside of Florida. 

Lower tidal mixed forests 

(LTmix) and lower tidal 

swamps (LTsw1 and LTsw2) 

are differentiated from upper 

tidal forests, in part, by the 

presence of Magnolia virginiana in the canopy. Lower tidal 

swamps have the highest density of canopy trees (about 

1,200 trees per hectare) of all 

floodplain forest types, with 

Nyssa biflora the most important canopy species by basal 

area.

Water use in the Suwannee 

River basin in Florida and Georgia 

is expected to increase over time 

because of anticipated growth and 

development in the region and adjacent areas. Increased consumption 

of water, supplied primarily from 

ground water, could reduce groundwater discharge to the Suwannee 

River thereby decreasing river 

flows. If flows were reduced, river 

stage would decrease and salinity 

would increase, having the following impacts on the forested floodplain.

• Drier species would invade 

wetland forest types of the riverine and upper tidal reaches if 

flow reductions reduced flood 

depths and long-term duration 

of inundation and saturation. 

Estimated impacts of specific 

flow reductions on each forest 

type were based on the 

percentage change of 5-year, 

14-day flood depths toward 

that of the next drier type. 

Five forest types were estimated to become drier and partially shift to the next drier 

forest type: Rsw1/sw2, Rblh1, 

Rblh2/blh3, UTmix, and 

UTblh. The total area of forests estimated to change to a 

drier type ranged from 52 to 

1,140 ha for flow reductions 

ranging from 2.8 to 56 m3

/s 

(100-2,000 ft3

/s), respectively, 

with the greatest changes 

occurring in riverine swamps.

• Tidal species would move 

upstream if flow reductions 

decreased flood depths at riverine/upper tidal and upper 

tidal/lower tidal reach boundaries. Estimated area of tidal 

forests expected to move 

upstream was based on 

upstream movement of the 

existing location of the 5-year, 

14-day flood depth at the reach 

boundaries for each flow 

reduction. Six forest types 

were expected to become more 

tidal: Rsw1/sw2, Rblh1, 

Rblh2/blh3, UTsw1/sw2, 

UTmix, and UTblh. The area 

of forests changing to a more 

tidal type could be estimated 

for only three of these forest 

types (Rsw1/sw2, Rblh1, and 

UTsw1/sw2), and totaled 36-

788 ha for flow reductions of 

2.8-56 m3

/s (100-2,000 ft3/s), 

respectively, with UTsw1/sw2 

forests experiencing the greatest impacts.

• Salt-intolerant species would 

retreat upstream if flow reductions increased salinity in the 

lower tidal reach. Estimated 

losses of forests at the tree line 

were based on the upstream 
92 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

movement of salinities at the 

tree line that would be 

expected if flows were 

reduced. Total area of forests 

estimated to change to marshes 

was 72-618 ha for flow reductions of 2.8-56 m3

/s (100-

2,000 ft3

/s), respectively, with 

changes occurring only in 

LTsw1/sw2 and LTmix. Other 

lower tidal forests upstream of 

the tree line would also be 

expected to change in composition to more salt-tolerant tree 

species if flows were reduced, 

but the area of forest change 

could not be estimated.

• The amount of inundated area 

in floodplain forests of the riverine reach would decrease if 

flows were reduced, even at 

low and medium flows when 

water in the floodplain is isolated from the main river channel. The generally good 

hydraulic connection between 

water levels in the floodplain 

and the river at low and 

medium flows may be due to 

the high permeability of subsurface sands and limestone. 

The amount of inundated area 

in riverine swamps is limited at 

low flows; therefore losses due 

to flow reductions at low flows 

would be relatively small in 

area, but large in percent of 

existing inundated area. If 

flow reductions from 2.8 to 

56 m3

/s (100-2,000 ft3/s) were 

to occur at the lowest recorded 

flow (61.7 m3

/s; 2,200 ft3/s), 

estimated losses of inundated 

area would range from 4 to 

17 ha, respectively, which is 

equivalent to a 24 to 100 percent loss of existing inundated 

area. Impacts would be greatest in riverine swamps, 

because nearly all inundated 

areas in the riverine reach 

existing at low flows are in 

swamps.

• The amount of saturated area 

in floodplain forests of the riverine reach would also 

decrease if flows were 

reduced. If flow reductions 

from 2.8 to 56 m3

/s (100-

2,000 ft3

/s) were to occur at the 

lowest recorded flow 

(61.7 m3

/s; 2,200 ft3/s), estimated losses of saturated area 

would range from 21 to 

624 ha, respectively. For all 

flow reductions below the 

median flow of 181 m3

/s 

(6,480 ft3

/s), estimated losses 

of saturated area were much 

greater than that of inundated 

area.

The ecological consequences of flow-reduction impacts 

on the forested floodplain would 

be diverse and numerous. If forests 

at the tree line were replaced by 

marshes, there would be a decrease 

in vertical structural diversity and 

woody micro-habitats such as 

fallen logs, tree cavities, and root 

mats, which are important to many 

animals. Additional losses of wetland forests would occur in the riverine and upper tidal reaches if 

bottomland hardwoods were 

invaded by upland species. Likely 

consequences of wetland losses 

would be increased vulnerability 

of drier areas to human disturbance, lower basal area and species richness in the forest 

community, and loss of preferred 

wildlife habitat. Flow reductions 

would have a greater impact on 

riverine swamps than any other 

forest type in the riverine and 

upper tidal reaches. If riverine 

swamps became drier, important 

swamp species such as Taxodium 

distichum and Nyssa aquatica

could have increased competition 

from opportunistic bottomland 

hardwoods or invasive exotic species. These drier swamps would 

not provide wildlife habitat equal 

in value to mature stands of either 

swamps or low bottomland hardwoods. Some organic soils would 

be lost from oxidation, decreasing 

the ability of riverine swamps to 

mitigate the effects of droughts by 

retaining water in the soil during 

dry periods. If floodplain soils 

became less saturated as a result of 

flow reductions, the ability of riverine forests to remove nitrates and 

other pollutants from river water 

could be diminished. Drier 

swamps at the floodplain-upland 

boundary could increase vulnerability to fire for all floodplain forests in the riverine reach. If flow 

reductions occurred during low 

and medium flows, the amount of 

inundated area in shallow ponds 

and sloughs of riverine swamps 

would decrease, eliminating 

aquatic habitats that are critical to 

the survival of fishes and aquatic 

invertebrates and important to 

many other animals that use the 

floodplain. If large flow reductions occurred during high flows, 

main channel fishes could decrease 

in diversity and abundance 

because they are seasonally dependent on flooded forests for food, 

shelter, and reproduction. In addition, aquatic organisms in the river 

and estuary could be adversely 

affected because they depend on 

particulate organic detritus and 

other floodplain exports as food 

sources.
References 93

REFERENCES

Allen, J.A., Chambers, J.L., and RezaPezeshki, S., 1997, Effects of 

salinity on baldcypress seedlings: 

Physiological responses and their 

relation to salinity tolerance: 

Wetlands, v. 17, no. 2, p. 310-320.

Applequist, M.B., 1959, Longevity of 

submerged tupelo gum and bald 

cypress seed: Louisiana State 

University, Forestry Notes 27, 2 p.

Baker, J.A., Killgore, K.J., and Kasul, 

R.L., 1991, Aquatic habitats and 

fish communities in the lower 

Mississippi River: Reviews in 

Aquatic Sciences, v. 3, no. 4, 

p. 313-356.

Benke, A.C., Henry, R.L., III, 

Gillespie, D.M., and Hunter, R.J., 

1985, Importance of snag habitat 

for animal production in 

southeastern streams: Fisheries, 

v. 10, no. 5, p. 8-13.

Berndt, M.P., Oaksford, E.T., Darst, 

M.R., and Marella, R.L., 1996, 

Environmental setting and factors 

that affect water quality in the 

Georgia-Florida Coastal Plain 

study unit: U.S. Geological 

Survey Water-Resources 

Investigations Report 95-4268, 

45 p.

Bradley, J.T., 1975, Freeze 

probabilities in Florida: 

Agricultural Experiment Stations, 

Institute of Food and Agricultural 

Sciences, University of Florida: 

Bulletin 777 (technical), 22 p.

Breil, David A., 1970, Liverworts of 

the Mid-Gulf Coastal Plain: The 

Bryologist, v. 73, p.409-491.

Brinson, M.M., 1990, Riverine forests, 

in Lugo, A.E., Brinso, M., and 

Brown, S., eds., Ecosystems of the 

world—Forested Wetlands: 

Elsevier, v. 15, p. 87-141.

Brinson, M.M., Bradshaw, H.D., and 

Kane, E.S., 1984, Nutrient 

assimulative capacity of an 

alluvial floodplain swamp: 

Journal of Applied Ecology, v. 21, 

p. 1041-1057.

Brinson, M.M., Swift, B.L., Plantico, 

R.C., and Barclay, J.S., 1981, 

Riparian ecosystems: Their 

ecology and status: U.S. Fish and 

Wildlife Service, FWS/OBS81/17, 154 p.

Brown, C.A., 1984, Morphology and 

biology of cypress trees, in Ewel, 

K.C., and Odum, H.T., eds., 

Cypress swamps: Gainesville, 

University Presses of Florida, 

p. 16-24.

Brown, K.E., 1973, Ecological life 

history and geographical 

distribution of the cabbage palm, 

Sabal palmetto: Raleigh, North 

Carolina State University, 

Department of Botany, PhD 

Thesis, 100 p.

Carr, Archie, 1983, All the way down 

upon the Suwannee River: 

Audubon, March edition, p. 80-101.

Carlton, Jedfrey M., 1977, A Survey of 

Selected Coastal Vegetation 

Communities of Florida: St. 

Petersburg, Florida Department of 

Natural Resources, Florida 

Marine Research Publication 

Number 30, 40 p.

Carter, Virginia, 1996, Wetland 

hydrology, water quality, and 

associated functions, in Fretwell, 

J.D., Williams, J.S., and Redman, 

P.J., compilers, National water 

summary on wetland resources: 

U.S. Geological Survey WaterSupply Paper 2425, p. 35-48.

Clark, Judith, 1979, Fresh Water 

wetlands: Habitats for aquatic 

invertebrates, amphibians, and 

fish, in Greeson, P.E., Clark J.R., 

and Clark, J.E., eds., Wetland 

functions and values: The state of 

our understanding—Proceedings 

of the national symposium on 

wetlands, Lake Buena Vista, 

Florida, November 1978: 

Minneapolis, American Water 

Resources Association, Technical 

Publication Series TPS79-2, 

p. 330-343.

Clark, J.R., and Benforado, J., eds., 

1981, Wetlands of bottomland 

hardwood forests— Proceedings 

of a workshop on bottomland 

hardwood forest wetlands of the 

southeastern United States, Lake 

Lanier, Georgia, June 1-5, 1980: 

Elsevier, Developments in 

Agricultural and Managed-Forest 

Ecology, v. 11, p. 335-357.

Clewell, A.F., 1985, Guide to the 

vascular plants of the Florida 

Panhandle: Tallahassee, Florida 

State University Press, 605 p.

Clewell, A.F., 1986, Natural setting 

and vegetation of the Florida 

Panhandle—An account of the 

environments and plant 

communities of northern Florida 

west of the Suwannee River: 

Mobile, Ala., U.S. Army Corps of 

Engineers, Contract No. 

DACW01-77-C-0104, 773 p.

Clewell, A.F., Beaman, R.S., Coultas, 

C.L., and Lasley, M.E., 1999, 

Suwannee River tidal marsh 

vegetation and its response to 

external variables and endogenous 

community processes: Live Oak, 

Fla., Suwannee River Water 

Management District, 118 p., plus 

15 appendices, variously paged.

Cohen, A.D., Casagrande, D.J., 

Andrejko, M.J., and Best, G.R, 

eds., 1984, The Okefenokee 

Swamp: Its natural history, 

geology, and geochemistry: Los 

Alamos, New Mexico, Wetland 

Surveys, 709 p.

Conner, W.H., and Askew, G.R., 1993, 

Impact of saltwater flooding on 

red maple, redbay, and Chinese 

tallow seedlings: Castanea, v. 58, 

no. 3, p. 214-219.

Conner, W.H., and Buford, M.A., 1998, 

Messina M.G., and Conner, W.H., 

eds., 1998, Southern forested 

wetlands—Ecology and 

management: New York, Louis 

Publishers, p. 261-287.

Coultas, C.L., 1984, Soils of swamps in 

the Apalachicola, Florida, estuary: 

Florida Scientist, v. 47, no. 2, 

p. 98-107.

Cowardin, L.M., Carter, Virginia, 

Golet, F.C., and LaRoe, E.T., 

1979, Classification of wetlands 

and deepwater habitats of the 

United States: U.S. Fish and 

Wildlife Service FWS/OBS79/31, 103 p.
94 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

Crane, J.J., 1986, An investigation of 

the geology, hydrogeology, and 

hydrochemistry of the lower 

Suwannee River basin: 

Tallahassee, Florida Geological 

Survey Report of Investigation 96, 

110 p.

Dahl, T.E., 1990, Wetlands losses in 

the United States 1780’s to 

1980’s: U.S. Fish and Wildlife 

Service, Report to Congress, 13 p.

Darst, M.R., Light, H.M., and Lewis, 

L.P., 2002, Ground-cover 

vegetation in wetland forests of 

the lower Suwannee River 

floodplain, Florida, and potential 

impacts of flow reductions: U.S. 

Geological Survey WaterResources Investigations Report 

02-4027, 46 p.

Darst, M.R., Light, H.M., and 

McPherson, B.F., 1996, Florida 

wetland resources, in Fretwell, 

J.D., Williams J.S., and Redman, 

P.J., compilers, National water 

summary on wetland resources: 

U.S. Geological Survey WaterSupply Paper 2425, p. 153-160.

Davis, M.M., 1990, Vegetative 

regeneration in wetland forests of 

Florida: Gainesville, University of 

Florida, Department of 

Philosophy, PhD Dissertation, 

195 p.

Davis, M.M., Mitchell, W.A., Wakeley, 

J.S., Fischenich, J.C., and Craft, 

M.M., 1996, Environmental value 

of riparian vegetation: U.S. Army 

Corps of Engineers, Technical 

Report EL-96-16, 147 p., plus 

appendixes.

DeBell, D.S., and Naylor, A.W., 1972, 

Some factors affecting 

germination of swamp tupelo 

seeds: Ecology, v. 53, no. 3, 

p. 504-506.

Demaree, Delzie, 1932, Submerging 

experiments with Taxodium: 

Ecology, v. 13, no. 3, p. 258-262.

Dickson, R.E., Hosner, J.F., and 

Hosley, N.W., 1965, The effects of 

four water regimes upon the 

growth of four bottomland tree 

species: Forest Science, v. 11, 

no. 3, p. 299-305.

DuBarry, A.P., 1963, Germination of 

bottomland tree seeds while 

immersed in water: Journal of 

Forestry, v. 61, no. 3, p. 225-226.

Elder, J.F., and Cairns, D.J., 1982, 

Production and decomposition of 

forest litter fall on the 

Apalachicola River flood plain: 

U.S. Geological Survey Water 

Supply Paper 2196-B, 42p.

Fanning, J.L., 1997, Water use in 

Georgia by county for 1995: 

Georgia Department of Natural 

Resources Information Circular 

101, 95 p.

Fisk, D.W., and Rosenau, J.C., 1977, 

Potentiometric surface of the 

Floridan aquifer in the Suwannee 

River Water Management District, 

north Florida, May 1976, U.S. 

Geological Survey WaterResources Investigation 77-1, 

1 sheet.

Fowells, H.A., compiler, 1965, Silvics 

of forest trees of the United States 

(revised): Washington, D.C., U.S. 

Department of Agriculture, Forest 

Service, Agriculture Handbook 

No. 271, 762 p.

Franklin, M.A., Giese, G.L., and 

Mixson, P.R., 1995, Statistical 

summaries of surface-water 

hydrologic data collected in the 

Suwannee River Water 

Management District, Florida, 

1906-93: U.S. Geological Survey 

Open-File Report 94-709, 173 p.

Franklin, M.A., Meadows, P.E., and 

Alvarez, A.E., 1999, Water 

resources data: Florida: Water 

year 1998: Vol. 4. Northwest 

Florida: U.S. Geological Survey 

Water-Data Report FL-98-4, 

169 p.

Fredrickson, L.H., 1979, Lowland 

hardwood wetlands: Current 

status and habitat values for 

wildlife, in Greeson, P.E., Clark 

J.R., and Clark, J.E., eds., Wetland 

functions and values: The state of 

our understanding—Proceedings 

of the national symposium on 

wetlands, Lake Buena Vista, 

Florida, November 1978: 

Minneapolis, American Water 

Resources Association, Technical 

Publication Series TPS79-2, 

p. 296-306.

Gill, C.J., 1970, The flooding tolerance 

of woody species—A review: 

Forestry Abstracts, v. 31, no. 4, 

p. 671-688.

Gleason, P.J., ed., 1974, Environments 

of South Florida: Present and past: 

Miami Geological Society, 

Memoir 2, 452 p.

Godfrey, R.K., 1988, Trees, shrubs, and 

woody vines of northern Florida 

and adjacent Georgia and 

Alabama: Athens, The University 

of Georgia Press, 734 p.

Gosselink, J.G., Lee, L.C., and Muir, 

T.A., eds., 1990, Ecological 

processes and cumulative impacts: 

Chelsea, Mich., Lewis Publishers, 

708 p.

Greeson, P.E., Clark, J.R., and Clark, 

J.E., eds., 1979, Wetland 

functions and values: The state of 

our understanding—Proceedings 

of the national symposium on 

wetlands, Lake Buena Vista, 

Florida, November 1978: 

Minneapolis, American Water 

Resources Association, Technical 

Publication Series TPS79-2, 

674 p.

Guillory, Vincent, 1979, Utilization of 

an inundated floodplain by 

Mississippi River fishes: Florida 

Scientist, v. 42, no. 4 p. 222-228.

Gunderson, L.H., 1986, Regeneration 

of cypress in logged and burned 

strands at Corkscrew Swamp 

Sanctuary, Florida, in Ewel, K.C., 

and Odum, H.T., eds., Cypress 

swamps (2d ed.): Gainesville, 

University Presses of Florida, 

p. 349-357.

Hanlon, E.A., McNeal, B.L., and 

Kidder, G., 1993, Soil and 

Container Media Electrical 

Conductivity Interpretations: 

Gainesville, Florida Cooperative 

Extension Service, Circular 1092, 

University of Florida, 10 p.

Harmon, M.E., Franklin, J.F., 

Swanson, F.J., Sollins, P., 

Gregory, W.V., Lattin, J.D., 

Anderson, N.H., Cline, S.P., 
References 95

Aumen, N.G., Sedell, J.R., 

Lienkaemper, G.W., Cromack, K., 

Jr., and Cummins, K.W., 1986, 

Ecology of coarse woody debris 

in temperate ecosystems, in 

MacFadyen, A., and Ford, E.D., 

eds., Advances in ecological 

research, v. 15: London, 

Academic Press, Harcourt Brace 

Javanovich, p. 133-302.

Harms, W.R., 1973, Some effects of 

soil type and water regime on 

growth of tupelo seedlings: 

Ecology, v. 54, no. 1, p. 188-193.

Harper, Francis, ed., 1958, The travels 

of William Bartram: Hew Have, 

Conn., Yale University Press, 

Naturalist’s edition, 727 p.

Hem, J.D., 1985, Study and 

interpretation of the chemical 

characteristics of natural water 

(3d ed.): U.S. Geological Survey 

Water-Supply Paper 2254, 263 p., 

3 plates.

Herring, B.J., and Judd, W.S., 1995, A 

floristic study of Ichetucknee 

Springs State Park, Suwannee and 

Columbia Counties, Florida: 

Castanea, v. 60, no. 4, p. 318-369.

Ho, F.P., and Tracey, R.J., 1975, Storm 

tide frequency analysis for the 

Gulf Coast of Florida, from Cape 

San Blas to St. Petersburg Beach: 

National Oceanic and 

Atmospheric Administration, 

Technical Memorandum NWS 

HYDRO-20, 34 p.

Hook, D.D., and Brown, C.L., 1973, 

Root adaptations and relative 

flood tolerance of five hardwood 

species: Forest Science, v. 19, 

no. 3, p. 225-229.

Hoover, J.J., and Killgore, K.J., 1998, 

Fish communities, in Messina 

M.G., and Conner, W.H., eds., 

1998, Southern forested 

wetlands—Ecology and 

management: New York, Louis 

Publishers, p. 238-260.

Hornsby, D., and Mattson, R., 1998, 

Surface water quality and 

biological monitoring network: 

Live Oak, Fla., Suwannee River 

Water Management District 

Annual Report WR-98-02, 130 p.

Hosner, J.F., 1960, Relative tolerance 

to complete inundation of 

fourteen bottomland tree species: 

Forest Science, v. 6, no. 3, p. 246-

251.

Hosner, J.F., and Boyce, S.G., 1962, 

Tolerance to water saturated soil 

of various bottomland hardwoods: 

Forest Science, v. 8, no. 2, p. 180-

186.

Howell, D.A., 1999, Floodplain 

geomorphology of the lower 

Suwannee River, Florida: 

Gainesville, University of Florida, 

Master’s Thesis, 81 p.

Interagency Advisory Committee on 

Water Data, 1982, Guidelines for 

determining flood flow frequency: 

Bulletin 17B of the Hydrology 

Subcommittee, Office of Water 

Data Coordination, U.S. 

Geological Survey, Reston 

Virginia, 183 p.

International Marine, 1995, Tide 

tables, 1996, High and low water 

predictions--East Coast of North 

and South America, including 

Greenland: Blacklick, Ohio, 

Division of McGraw Hill, 

unabridged, 380 p.

Johnson, Lamar, 1974, Beyond the 

fourth generation: Gainesville, 

University Presses of Florida, 

230 p.

Katz, B.G., DeHan, R.S., Hirten, J.J., 

and Catches, J.S., 1997, 

Interactions between ground 

water and surface water in the 

Suwannee River Basin, Florida: 

Journal of the American Water 

Resources Association, v. 33, 

no. 6, p. 1-18.

Killgore, K.J., and Baker, J.A., 1996, 

Patterns of larval fish abundance 

in a bottomland hardwood 

wetland: Wetlands, v. 16, no. 3, 

p. 288-295.

Kjerfve, Bjorn, 1976, The SanteeCooper: A study of estuarine 

manipulations, in Wiley, Martin, 

ed., Estuarine processes—Uses, 

stresses, and adaptation to the 

estuary: Academic Press, v. 1, 

p. 44-56.

Kovacic, Ciravolo, T.G., McLeod, 

K.W., and Erwin, J.W., 1990, 

Potential nitrate leaching losses 

and nitrogen mineralization in an 

Atlantic Coastal Plain watershed 

following disturbance: 

Preliminary results, in Gosselink, 

J.G., Lee, L.C., and Muir, T.A, 

eds., 1990, Ecological processes 

and cumulative impacts: Chelsea, 

Mich., Lewis Publishers, p. 103-

122.

Kurz, Herman, and Wagner, Kenneth, 

1957, Tidal marshes of the Gulf 

and Atlantic Coasts of northern 

Florida and Charleston, South 

Carolina: Tallahassee, Florida 

State University Studies, no. 24, 

168 p.

Langeland, K.A., and Burkes, K.C., 

eds., 1998, Identification and 

biology of non-native plants in 

Florida’s natural areas: 

Gainesville, University of Florida, 

IFAS Distribution, 165 p.

Larson, J.S., Bedinger, M.S., Bryan, 

C.F., Brown, Sandra, Huffman, 

R.T., Miller, E.L., Rhodes, D.G., 

and Touchet, B.A., 1981, 

Transition from wetlands to 

uplands in southeastern 

bottomland hardwood forests, in

Clark, J.R., and Benforado, J., 

eds., 1981, Wetlands of 

bottomland hardwood 

forests—Proceedings of a 

workshop on bottomland 

hardwood forest wetlands of the 

southeastern United States, Lake 

Lanier, Georgia, June 1-5, 1980: 

Elsevier, Developments in 

Agricultural and Managed-Forest 

Ecology, v. 11, p. 225-273.

Leitman, H.M., Darst, M.R., and 

Nordhaus, J.J., 1991, Fishes in the 

forested flood plain of the 

Ochlockonee River, Florida, 

during flood and drought 

conditions: U.S. Geological 

Survey Water-Resources 

Investigations Report 90-4202, 

36 p.

Leitman, H.M., Sohm, J.E., and 

Franklin, M.A., 1984, Wetland 

hydrology and tree distribution of 
96 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

the Apalachicola River flood 

plain, Florida: U.S. Geological 

Survey Water-Supply Paper 2196-

A, 52 p.

Lewis, L.J., Light, H.M., and Darst, 

M.R., 2002, Location and 

description of transects for 

ecological studies in floodplain 

forests of the lower Suwannee 

River, Florida: U.S. Geological 

Survey Open-File Report 01-410, 

84 p.

Light, H.M., and Darst, M.R., 1997, 

Appendix B–Habitat 

characterization data for 

floodplain sites on the upper, 

middle, and non-tidal lower 

Apalachicola River, Florida, in

Davis, M.M., Tri-State 

comprehensive study riparian 

wetland element: Report I: 

Relationships between flow and 

habitat value in the AlabamaCoosa-Tallapoosa/ApalachicolaChattahoochee-Flint (ACT/ACF) 

River Basins: Vicksburg, Miss., 

U.S. Army Corps of Engineer 

Waterways Experiment Station, 

Miscellaneous Paper EL-97-2, 

p. B1-B24.

Light, H.M., Darst, M.R., and Grubbs, 

J.W., 1998, Aquatic habitats in 

relation to river flow in the 

Apalachicola River floodplain, 

Florida: U.S. Geological Survey 

Professional Paper 1594, 77 p., 

3 plates.

Light, H.M., Darst, M.R., 

MacLaughlin, M.T., and Sprecher, 

S.W., 1993, Hydrology, 

vegetation, and soils of four north 

Florida river flood plains with an 

evaluation of State and Federal 

wetland determinations: U.S. 

Geological Survey WaterResources Investigations Report 

93-4033, 94 p.

Little, E.L., Jr., 1978, Atlas of United 

States trees: U.S. Department of 

Agriculture Forest Service, 

Miscellaneous Publication 

No. 1361, 22 p., plus 6 general 

maps and 256 species maps.

Lugo, A.E., Brinson, M., and Brown, 

S., eds., 1990, Ecosystems of the 

world—Forested Wetlands: 

Elsevier, v. 15, 527 p.

Mahon, G.L., Choquette, A.F., and 

Sepulveda, A.A., 1997, 

Potentiometric surface of the 

Upper Floridan aquifer in the 

Suwannee River Water 

Management District, Florida, 

May and June 1996: U.S. 

Geological Survey Open-File 

Report 96-617, 1 sheet.

Marella, R.L., 1995, Water-use data by 

category, county, and water 

management district in Florida, 

1950-90: U.S. Geological Survey 

Open-File Report 94-521, 114 p.

Marella, R.L., 1999, Water 

withdrawals, use, discharge, and 

trends in Florida, 1995: U.S. 

Geological Survey WaterResources Investigations Report 

99-4002, 90 p.

Mattoon, W.R., 1915, The southern 

cypress: U.S. Department of 

Agriculture Bulletin 272, 74 p.

Mattson, R.A., and Krummrich, Jerry, 

1995, Determination of salinity 

distributions in the upper 

Suwannee River Estuary: 

Cooperative project of the Florida 

Game and Fresh Water Fish 

Commission and the Suwannee 

River Water Management District, 

unpaginated [unpublished final 

report], 49 p.

McCarron, J.K., McLeod, K.W., and 

Conner, W.H., 1998, Flood and 

salinity stress of wetland woody 

species, buttonbush 

(Cephalanthus occidentalis) and 

swamp tupelo (Nyssa sylvatica

var. Biflora), Wetlands, v. 18, 

no. 2, p. 165-175.

McKee, K.L., and Mendelssohn, I.A., 

1989, Response of a freshwater 

marsh plant community to 

increased salinity and increased 

water level: Aquatic Botany, v. 34, 

p. 301-316.

McPherson, Kelly, and Williams, 

Kimberlyn, 1996, Establishment 

growth of cabbage palm, Sabal 

palmetto (Arecaceae): American 

Journal of Botany, v. 83, no. 12, 

p. 1566-1570.

Meadows, P.E., 1991, Potentiometric 

surface of the Upper Floridan 

aquifer in the Suwannee River 

Water Management District, 

Florida, May 1990, U.S. 

Geological Survey Open-File 

Report 90-582, 1 sheet.

Meyer, K.D., 1998, Communal roosts 

of the American swallow-tailed 

kite in Florida: Habitat 

associations, critical sites, and a 

technique for monitoring 

population status: Tallahassee, 

Florida Game and Fresh Water 

Fish Commission, Final Report, 

56 p.

Messina M.G., and Conner, W.H., eds., 

1998, Southern forested 

wetlands—Ecology and 

management: New York, Louis 

Publishers, 616 p.

Mitsch, W.J., and Gosselink, J.G., 

2000, Wetlands (3rd ed.): New 

York, John Wiley & Sons, Inc., 

920 p.

Monk, C.D., 1966, An ecological study 

of hardwood swamps in northcentral Florida: Ecology, v. 47, 

no. 4, p. 649-654.

Mueller-Dombois, Dieter, and 

Ellenberg, Heinz, 1974, Aims and 

methods of vegetation ecology: 

New York, John Wiley, 547 p.

National Oceanic and Atmospheric 

Administration, 1994, Superstorm 

of March 12-14, 1993: Silver 

Spring, Md., National Weather 

Service, Natural Disaster Survey 

Report, variously paged.

Organization of American States, 

1991, Hurricane hazards, in

Primer on natural hazard 

management in integrated 

regional development planning: 

Washington, D.C., Department of 

Regional Development and 

Environment Executive 

Secretariat for Economic and 

Social Affairs, Chapter 12, 26 p., 

URL 

http://www.oas.org/usde/publica

tions/Unit/oea66e/ch12.html.

Orlando, S.P., Jr., Rozas, L.P., Ward, 

G.H., and Klein, C.J., 1993, 

Salinity characteristics of Gulf of 
References 97

Mexico estuaries: Silver Spring, 

Md., National Oceanic and 

Atmospheric Administration, 

Office of Ocean Resources, 

Conservation and Assessment, 

209 p.

Owenby, J.R., and Ezell, D.S., 1992, 

Monthly station normals of 

temperature, precipitation, and 

heating and cooling degree days 

1961-90: U.S. Department of 

Commerce, National Oceanic and 

Atmospheric Administration, 

National Climatic Data Center, 

Asheville, North Carolina: 

Climatography of the United 

States No. 81, 26 p. 

Penfound, W.T., 1952, Southern 

swamps and marshes: The 

Botanical Review, v. XVIII, no. 7, 

p. 413-446.

Penfound, W.T., and Hathaway, E.S., 

1938, Plant communities in the 

marshlands of southeastern 

Louisiana: Ecological 

Monographs, v. 8, no. 1, p. 3-56.

Perry, L., and Williams, K., 1996, 

Effects of salinity and flooding on 

seedlings of cabbage palm (Sabal 

palmetto): Springer-Verlag, 

Oecologia, v. 105, p. 428-434.

Pezeshki, S.R., Delaune, R.D., and 

Patrick, W.H., Jr., 1987, Response 

of baldcypress (Taxodium 

distichum L. var. distichum) to 

increases in flooding salinity in 

Louisiana’s Mississippi River 

deltaic plain, Wetlands, v. 7, no. 1, 

p. 1-10.

Pezeshki, S.R., DeLaune, R.D., and 

Patrick, W.H., Jr. 1990, Flooding 

and saltwater intrusion: Potential 

effects on survival and 

productivity of wetland forests 

along the U.S. Gulf Coast: 

Elsevier, Forest Ecology and 

Management, v. 33, no. 34, 

p. 287-301.

Pierce, R.R., Barber, N.L., and Stiles, 

H.R., 1984, Georgia irrigation, 

1970-80: A decade of growth: 

U.S. Geological Survey WaterResources Investigations Report 

83-4177, 29 p.

Ponnamperuma, F.N., 1972, The 

chemistry of submerged soils, in

Brady, N.C., ed., Advances in 

Agronomy: New York, Academic 

Press, v. 24, p. 29-96.

Puri, H.S., and Vernon, R.O., 1964, 

Summary of the geology of 

Florida and a guidebook to the 

classic exposures (revised): 

Tallahassee, Florida Geological 

Survey, Special Publication no. 5, 

312 p.

Raabe, Ellen, 2000, Coastal forest 

retreat on Florida’s Big Bend Gulf 

Coast: U.S. Geological Survey, 

Center for Coastal Geology, URL 

http://coastal.er.usgs.gov/

wetlands/forest-retreat/.

Raabe, E.A., Marth, N.J., and Stumpf, 

R.P., 2000, GPS Surveying of 

estuarine sites and water level 

gages in the lower Suwannee 

River watershed: U.S. Geological 

Survey Open-File Report 00-296, 

17 p.

Reed, P.B., Jr., 1988, National list of 

plant species that occur in 

wetlands: 1988 - Florida: St. 

Petersburg, Florida National 

Wetlands Inventory, U.S. Fish and 

Wildlife Inventory, U.S. Fish and 

Wildlife Service, 140 p.

Richards, L.A., ed., 1954, Diagnosis 

and improvement of saline and 

alkali soils: U.S. Department of 

Agriculture Handbook 60, 160 p.

Rosenau, J.C., and Meadows, P.E., 

1986, Potentiometric surface of 

the Upper Floridan aquifer in the 

Suwannee River Water 

Management District, Florida, 

May 1985: U.S. Geological 

Survey Water-Resources 

Investigations Report 86-4184, 

1 sheet.

Rosenau, J.C., and Milner, R.S., 1986, 

Potentiometric surface of the 

Upper Floridan aquifer in the 

Suwannee River Water 

Management District, Florida, 

May 1980: U.S. Geological 

Survey Open-File Report 81-211, 

1 sheet.

Ross, S.T., and Baker, J.A., 1983, The 

response of fishes to periodic 

spring floods in a southeastern 

stream: The American Midland 

Naturalist, v. 109, no. 1, 13 p.

Savino, J.F., and Stein, R.A., 1982, 

Predator-prey interaction between 

largemouth bass and bluegills as 

influenced by simulated, 

submersed vegetation: 

Transactions of the American 

Fisheries Society, v. 111, no. 3, 

p. 255-266.

Schitoskey, Frank, Jr., and Linder R.L., 

1979, Use of wetlands by upland 

wildlife, in Greeson, P.E., Clark 

J.R., and Clark, J.E., eds., Wetland 

functions and values: The state of 

our understanding—Proceedings 

of the national symposium on 

wetlands, Lake Buena Vista, 

Florida, November 1978: 

Minneapolis, American Water 

Resources Association, Technical 

Publication Series TPS79-2, 

p. 307-311

Siegel, E.M., Weisberg, R.H., 

Donovan, J.C., and Cole, R.D., 

1996, Physical factors affecting 

salinity intrusions in wetlands: 

The Suwannee River Estuary: St. 

Petersburg, University of South 

Florida, Department of Marine 

Science, 127 p.

Sniffen, R.P., 1981, Benthic 

invertebrate production during 

seasonal inundation of a 

floodplain swamp: Ph.D. 

Dissertation, University of North 

Carolina, Chapel Hill, 176 pp. 

Spohrer, M.L., 1976, Edaphic 

requirements of bottomland 

hardwoods and the effects of 

water level and sedimentation; a 

bibliography with abstracts: Baton 

Rouge, Louisiana State 

University, Louisiana Cooperative 

Wildlife Research Unit Special 

Publication Number 2.

Tillis, G.M., 2000, Flow and salinity 

characteristics of the upper 

Suwannee River Estuary, Florida: 

U.S. Geological Survey WaterResources Investigations Report 

99-4268, 40 p.
98 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential

Impacts of Flow Reductions

U.S. Army Corps of Engineers, 1974, 

Suwannee River floods, Florida 

and Georgia: Jacksonville, Fla., 

Special flood hazard information, 

17 p., plus 41 plates.

U.S. Department of Agriculture, 1996, 

Soil survey laboratory methods 

manual: Natural Resources 

Conservation Service, Soil Survey 

Investigations Report 42, version 

3.0, 693 p.

U.S. Department of Agriculture, 1999, 

Soil taxonomy—A basic system 

of soil classification for making 

and interpreting soil surveys 

(2d ed.): Natural Resources 

Conservation Service Agriculture 

Handbook 436, 869 p.

U.S. Geological Survey, 1974, 

Hydrologic unit map-1974, State 

of Florida: 1 sheet.

U.S. Geological Survey, 2001, Water 

use in the United States, URL 

http://water.usgs.gov/public/

watuse

Vince, S.W., Humphrey, S.R., Simons, 

R.W., 1989, The ecology of hydric 

hammocks: A community profile: 

Washington, D.C., U.S. Fish and 

Wildlife Service, National 

Wetlands Research Center, 

Biological Report 85(7.26), 81 p.

Welcomme, R.L., 1979, Fisheries 

ecology of floodplain rivers: New 

York, Longman, Inc., 317 p.

Wharton, C.H., Kitchens, W.M., and 

Sipe, T.W., 1982, The ecology of 

bottomland hardwood swamps of 

the southeast: A community 

profile: U.S. Fish and Wildlife 

Service FWS/OBS- 81/37, 133 p.

Wigley, T.B., and Lancia, 1998, 

Wildlife communities, in Messina 

M.G., and Conner, W.H., eds., 

1998, Southern forested 

wetlands—Ecology and 

management: New York, Louis 

Publishers, p. 205-236.

Willams, Kimberlyn, Ewel, K. C., 

Stumpf, R. P., Putz, F. E., and 

Workman, T. W., 1999, Sea-level 

rise and coasal forest retreat on 

the west coast of Florida, USA: 

Ecology, v, 80, no., 6, p. 2045-

2063.

Williams, Kimberlyn, Meads, M.V., 

and Sauerbrey, D.A., 1998, The 

roles of seedling salt tolerance and 

resprouting in forest zonation on 

the west coast of Florida, USA: 

American Journal of Botany, 

v. 85, no. 12, p. 1745-1752.

Wunderlin, R.W., and Hansen, Bruce, 

2000, Atlas of Florida vascular 

plants: Miami, University of 

South Florida, Institute for 

Systematic Botany, URL 

http://www.plantatlas.usf.edu/

and http://www.usf.edu/~isb/

projects/atlas/maps/
Appendixes
100 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions
Appendix I 101

Appendix I. Median monthly high, median daily high, and median daily 

low stages at transects and gages in tidal reaches of the lower 

Suwannee River, Florida

[rkm, river kilometers; m, meters]

Transect or gage Location, 

in rkm

Median 

monthly high 

(MMH),

in m above

sea level

Median daily 

high (MDH), 

in m above 

sea level

Median daily 

low(MDL),

in m above 

sea level

MS transect 42.49 1.18 0.99 0.67

KN and KI transects 31.21 1.01 0.86 0.35

TK transect 19.90 0.96 0.78 0.10

SN and SH transects 12.87 0.95 0.75 -0.05

Gopher River gage 9.06 0.90 0.68 -0.16

Upper West Pass gage 4.47 0.84 0.62 -0.31

Appendix II. Median land-surface elevations of forest types at transects in the floodplain of the lower Suwannee River, Florida

Transect Median land-surface elevation for indicated forest type, in meters above sea level

Rsw1 Rsw2 Rsw1/sw21

1

Data for specific forest types were weighted by the proportion of the area they covered in the forest map before being combined to create data for general forest types.

Rblh1 Rblh2 Rblh3 Rblh2/blh31 Upland2

2

Median land-surface elevations for uplands within the 10-year floodplain were estimated to be the water-surface elevation of the 10-year, 1-day high 

flow at each transect that has an adequate stage-discharge relation.

CF 4.30 4.67 4.57 5.34 6.82 6.55 6.68 8.41

LL 2.93 3.21 3.13 3.58 4.62 4.94 4.79 6.36

FK 1.83 1.87 1.86 2.90 4.03 4.03 5.41

MS (blh) 1.55 1.88 2.46 2.18 3.75

UTsw1 UTsw2 UTsw1/sw21 UTmix UTblh Upland2

MS (sw) 0.98 1.03 1.01

KN & KI 0.90 0.90 0.90 1.09 1.57 2.84

LTsw1 LTsw2 LTsw1/sw21 LTmix LTham Upland2

TK 0.76 0.76 0.76 1.84

SN 0.75

SH 1.03

BC 0.70 0.75 0.73 0.85

LK & DM 0.42 0.38 0.40 0.54
102 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

Appendix III. Floodplain hydrology observations and measurements 

made at study sites in floodplain forests of the lower Suwannee River, 

Florida

[m, meters; inun, inundated; sat, saturated; m3/s, cubic meters per second; ft3/s, cubic 

feet per second; ~, approximately; rkm, river kilometers]

This appendix contains the following sections:

A CF transect

B LL transect

C FK transect

D MS transect

E KN and KI transects

F TK transect

G SN transect

H SH transect

I BC transect

J LK and DM transects

K Verification plots
Appendix III 103

A CF transect

Distance from 

beginning of 

transect, in m

Soil moisture observation;

water-surface elevation, in m above sea level; or flow observation

7/25/97 11/13/97 12/9/97 5/12/98 6/16/98 7/8/98 9/8/98 3/25/99 6/29/99 9/8/99

0.0 inun dry dry dry

5.0 sat

9.9 dry dry dry dry dry dry

16.0 sat

22.0 sat dry

22.0 5.065 5.111 5.041 no water

24.6 dry sat dry dry sat dry

47.0 4.734 no water

sat

4.609

no flow

5.111

no flow

no water

sat

no water

dry 4.643 no waterdry

54.0 dry inun dry dry dry dry

63.0 sat

75.5 dry sat dry dry dry dry

94.4 dry dry dry dry dry dry

123.0 dry dry dry dry dry dry

137.0 dry

152.0 dry dry dry dry dry dry

167.0 sat

174.0 sat

181.3 dry sat dry dry dry dry

200.9 4.555 4.434

no flow

5.201

no flow 4.890 4.661 4.399 no water

203.9 inun inun inun inun dry

205.9 sat

230.8 inun inun inun inun sat

245.0 sat

256.8 inun inun inun inun sat

263.0 4.064

285.0 4.555 4.432

no flow

4.487

no flow 4.993 4.890 4.383 no water

285.2 sat

285.7 inun inun

288.7 dry inun sat dry dry

310.7 dry dry dry dry dry

1063.0 dry dry dry

1075.8 dry dry dry

1089.3 dry

1102.7 sat sat sat sat dry

1123.0 sat sat sat dry dry

1146.7 inun inun sat dry

1153.0 4.404

no flow

4.606

no flow

4.773

no flow 4.468 4.465 4.419 4.352 no water

1153.0 inun sat

1156.2 sat

1167.7 sat

1171.2 inun inun inun inun inun sat dry

1186.3 sat

1191.3 sat inun sat sat sat sat dry

Measured stage in Suwannee River, in m above sea level

2.952 4.388 4.742 4.803 3.282 2.906 3.078 2.827 2.009 2.009

Mean daily flow1 in Suwannee River, in m3/s (ft3/s)

1

Flow at Branford-Fort White derived from transect stage-discharge rating.

153

(5,454)

287

(10,244)

328

(11,705)

335

(11,968)

180

(6,415)

149

(5,326)

163

(5,811)

143

(5,106)

85

(3,019)

85

(3,019)
104 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

B LL transect

Distance from 

beginning of 

transect, in m

Soil moisture observation;

water-surface elevation, in m above sea level; or flow observation

10/11/96 10/28/96 8/5/97 12/8/97 6/10/98 6/11/98 1/12/99 6/28/99 9/7/99

0.0 dry dry dry dry

31.8 dry dry dry dry

69.2 dry dry dry dry

104.5 dry dry dry dry

110.6 dry sat dry dry dry dry

113.6 dry dry dry dry

140.3 dry dry dry dry

162.9 dry sat dry dry

184.2 sat sat dry dry

194.3 2.799 2.768 2.587 3.324

flowing 2.634 2.628 2.546 1.975

193.2 sat

198.7 sat

215.4 sat

246.2 sat sat dry

270.7 dry dry dry dry

282.7 sat sat dry dry

305.7 inun

flowing

inun

flowing dry

324.2 inun inun inun inun dry

328.2 sat

334.7 sat

349.2 inun inun sat dry

389.4 2.837 2.719 3.320

flowing 2.753 2.731

no flow 2.628 no water

dry

400.3 sat sat dry dry

416.7 sat

417.0 sat sat dry dry

437.7 dry dry dry dry

467.7 sat dry dry dry

486.3 dry dry dry dry

548.2 sat dry dry dry

569.0 sat dry dry dry

612.6 sat sat sat dry

667.1 dry dry dry dry

699.0 dry dry dry dry

719.3 dry dry dry dry

750.6 dry dry

768.0 dry dry dry

822.4 dry dry

868.2 dry dry

916.6 dry dry

913.2 inun inun

940.0 inun 2.908 inun

no flow

2.772

no flow

1057.6 sat sat

1068.0 2.806 2.765

flowing

2.679

flowing

Measured stage in Suwannee River, in m above sea level

2.696 2.699 2.368 3.321 2.382 2.349 1.754 1.229 1.269

Measured flow1 in Suwannee River, in m3/s (ft3/s)

1

 Flow at Branford-Fort White derived from transect stage-discharge rating.

234

(8,352)

234

(8,366)

194

(6,916)

323

(11,548)

195

(6,967)

191

(6,828)

128

(4,562)

78

(2,802)

82

(2,932)
Appendix III 105

C FK transect

Distance from 

beginning of 

transect, in m

Soil moisture observation;

water-surface elevation, in m above sea level; or flow observation

6/13/97 11/12/97 3/27/98 7/29/98 7/30/98 1/13/99 6/29/99 9/7/99

8.5 dry dry dry dry

40.0 dry dry dry dry

72.0 dry dry dry dry

103.6 dry sat dry dry

131.1 sat dry dry

144.1 dry sat dry dry

164.7 dry

185.3 sat sat dry dry

201.3 1.763 2.209 

flowing

no water

sat 1.772 no water no water

210.3 sat inun dry dry

956.5 sat sat dry dry

930.4 sat sat sat dry

922.9 sat

908.9 sat sat sat sat

891.5 1.8451

1

 Data collected on 6/12/97.

no water

sat 1.847 no water no water 

888.4 sat sat sat sat

881.3 dry

876.5 inun sat

864.4 dry

855.3 sat inun sat sat

845.3 dry

838.9 sat inun sat sat

817.7 sat inun sat sat

809.2 sat

805.2 sat sat sat dry

795.8 sat

789.8 sat sat

Measured stage in Suwannee River, in m above sea level

1.73 2.34 6.13 1.39 1.39 1.35 0.95 1.17

Mean daily flow2 in Suwannee River, in m3/s (ft3/s)

2

 Flow at Branford-Fort White derived from transect stage-discharge rating.

193

(6,903)

291

(10,410)

1451

(51,834)

146

(5,231)

146

(5,231)

141

(5,025)

90

(3,216)

117

(4,178)
106 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

D MS transect

Distance from 

beginning of 

transect, in m

Soil moisture observation; water-surface elevation, in m above sea level; or flow observation1

1

 Local time of observation or water-level measurement in brackets.

1/16/97 1/17/97 7/1/97 9/8/97 10/20/97 10/7/98 3/24/99 4/20/99 6/29/99 9/8/99

0.0 dry sat sat sat sat dry

36.7 sat inun

48.2 dry inun dry dry dry dry

102.6 dry sat dry dry dry dry

150.5 dry dry dry dry dry dry

200.0 dry dry dry dry dry dry

225.9 sat

238.1 sat inun sat sat sat sat

261.0 sat inun sat sat sat sat

291.5 sat inun sat sat sat sat

307.9

0.996

[17:35]

0.801

[17:45]

1.880

[12:17]

flowing

0.968

[16:20]

0.926

[11:50]

0.968

[13:04]

0.837

[9:50]

325.4 inun sat sat

358.7 inun sat sat

391.7 inun sat sat

416.2 inun inun

420.7 inun sat sat

452.7 inun dry dry

453.2 inun

454.2 inun

458.2 inun

461.2 inun

475.4 inun sat sat

515.4 inun sat sat

533.4 sat

553.1 inun dry dry

590.7 inun sat dry

626.2 sat

639.2 inun dry dry

676.2 inun sat sat

704.0 inun dry sat

737.8 inun sat sat

755.0

1.045

[15:30]

1.029

[15:05]

0.873

[15:30]

1.877

[13:43]

0.840

[13:35]

0.798

[10:50]

770.0 sat

774.0 inun sat dry

804.3 inun dry dry

845.0 inun dry dry

889.5 dry dry dry

917.4 dry dry dry

931.4 sat

932.0

1.107

[14:00]

1.108

[11:00]

0.927

[16:50]

1.913

[14:38]

0.768

[14:15]

no water

 [11:30]

945.4 sat

970.1 inun sat dry

1003.7 dry dry

Measured stage1 in Suwannee River, in m above sea level

1.112

[12:15]

0.777

[17:35]

0.748

[17:35]

1.942

[15:00]

0.801

[14:31]

Mean daily stage2 in Suwannee River, in m above sea level

2

 Interpolated between gages.

1.05 0.84 0.89 0.82 0.56 1.92 0.73 0.63 0.71 0.76

Mean daily flow3 in Suwannee River, in m3/s (ft3/s)

3

 Flow at Branford-Fort White derived from transect stage-discharge rating.

232 176 190 170 105 402 148 122 143 155

(8,284) (6,287) (6,769) (6,088) (3,767) (14,370) (5,300) (4,350) (5,104) (5,524)
Appendix III 107

E KN and KI transects

Distance from, 

beginning of 

transect,in m

Soil moisture observation; water-surface elevation, in m above sea level; or flow observation1

1

 Local time of observation or water-level measurement in brackets. 3 Interpolated between gages.

5/12/97 5/13/972

2

 Additional observations in field notes. 4 Flow at Branford-Fort White lagged 4 days before date of field visit.

6/2/97 6/3/97 10/20/97 1/28/98 4/30/98 7/30/982 1/14/99 6/29/99 9/7/99

0.0 dry dry dry dry

50.1 sat sat sat sat sat

55.4 inun

55.4

0.911

 [11:46] 0.118

[15:40]

0.688

 [12:02]

 flow out

0.401

[10:52]

flow in

0.420

[10:24]

flow out

0.746

[11:37]

flow in 0.167

 [13:50]

75.5 sat sat sat sat sat

98.8 inun sat sat sat sat sat

121.8 inun sat sat sat sat sat

148.7 sat sat sat sat sat

153.7 inun

179.0 sat sat sat sat sat

184.3 inun

217.0 sat sat sat sat sat

248.3 sat sat sat sat sat

253.0

and

232.3

 (tidal creek)

0.894 

[14:00-

14:25]

flow out

0.816 

[11:20] 

slack tide

0.733 

[11:10] 0.619 

[15:05]

no flow

0.737

 [11:15]

 flow out

0.668 

[10:32]

flow out 0.635

 [10:09]

 flow out

0.709

 [11:21]

 flow in 0.941 

[15:35] 

slack tide

0.920 

[14:07]

0.677

 [12:32]

0.668

 [12:02]

276.7 sat sat sat sat sat

298.0 sat sat inun sat sat sat

321.7 sat sat sat sat sat sat

346.0 inun sat sat sat sat sat

380.8 sat sat sat sat sat

406.7 sat sat sat sat sat

439.1 sat sat sat sat sat

464.1 inun sat sat sat sat sat

507.6 inun sat sat sat sat sat

536.2 dry dry dry

538.5 sat sat sat sat sat

560.0 sat sat sat

569.0 inun sat sat sat sat sat

590.2 sat sat sat sat sat

611.4 sat sat sat sat sat

632.1 inun sat inun inun sat sat

640.3 0.609

[14:30]

0.926

[13:27]

0.673

[9:29]

0.812

[10:36]

659.1 sat sat sat sat sat sat

668.3 0.966

[9:50] 

0.932

[11:37]

0.921

[9:45] no water

[14:30] 

0.929

[9:25]

0.917

[9:49] no water

[9:20]

sat

0.810

[10:32]

sat 0.928

[17:35]

0.915

[16:44]

0.926

[13:30]

 no flow

0.917

[14:13]

677.7 sat sat inun sat sat sat

704.1 dry sat sat sat sat

729.3 dry sat sat sat sat

729.3 1.748

[~10:00]

1.645

[12:05]

sheet flow

KI - 0.0 sat sat sat

KI - 2.0 sat

KI - 36.9 dry dry dry dry

KI - 74.0 dry dry dry dry

KI - 100.0 dry dry dry dry

Measured stage1

 in Suwannee River, in m above sea level

0.809

[15:35]

0.830

[11:39] 0.778

[11:48]

0.095

[15:30]

0.671

[12:08]

0.397

[10:32]

0.751

0.934 [11:58]

[13:37]

Daily high stage3

 in Suwannee River, in m above sea level

0.92 0.94 0.92 0.65 1.70 1.62 0.77 0.94 0.85 0.93

Mean daily flow4

 in Suwannee River, in m3/s (ft3/s)

333 320 180 185 94 521 459 148 131 76 79

(11,900) (11,430) (6,440) (6,620) (3,359) (18,590) (16,410) (5,290) (4,679) (2,721) (2,834)
108 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

F TK transect

Distance from 

beginning of 

transect, in m

Soil moisture observation; water-surface elevation, in m above sea level; or flow observation1

1

 Local time of observation or water-level measurement in brackets.

4/2/972

2

 Additional observations in field notes.

4/3/972 9/9/97 10/21/972 1/28/98 9/9/982 2/19/99 3/24/99 6/28/992 9/7/99

-2.7 dry

0 sat sat sat sat sat sat

29.6 sat inun inun sat sat inun

42.1 inun

54.6 sat inun inun sat sat inun

84.3 sat inun inun sat sat sat

95

0.720

[16:05]

no flow

0.705

[9:45] 0.583

[15:22]

0.516

[16:55]

0.885

[14:35]

sheet flow

0.825

[10:53]

sheet flow 0.801

[15:34]

no flow

0.702

[14:04]

0.635

[14:30]

0.760

[14:01] 0.699

[15:35]

0.809

[13:39]

sheet flow

110.5 sat inun inun sat sat inun

125.5 inun inun

140.4 inun inun sat sat

173.1 sat inun inun sat inun

205.9 sat sat sat inun

241.4 sat sat inun inun

262 inun inun 

flow out

271 sat sat inun inun

285.5 [11:15]

flow in

[11:45]

slack tide

0.484

[11:29]

flow out

0.359

[16:35]

flow out

0.506

[12:09]

flow out

0.771

[15:45]

flow in

0.802

[14:50]

0.884

[14:12]

flow in

0.689

[12:50]

flow out

1.258

[12:34]

flow out

0.484

[13:23]

flow out

0.817

[15:05]

flow in

0.612

[14:50]

flow out

0.377

[14:45]

flow out

305.8 inun inun inun inun inun

333 sat sat sat sat

361.1 inun inun sat inun

392.2 inun inun sat inun

411.9 sat sat sat sat

Measured stage1 in Suwannee River, in m above sea level

0.652

[14:20]

0.208

[13:55]

0.289

[16:45]

0.290

[12:43]

0.792

[15:54]

0.810

[15:00]

flow in

0.893

[14:26]

0.185

[14:08]

0.181

[14:16]

Daily high stage in Suwannee River, in m above sea level

0.59 0.80 0.77 0.64 1.13 0.93 0.82 0.89

Mean daily flow3 in Suwannee River, in m3/s (ft3/s)

3

 Flow at Branford-Fort White lagged 5 days before date of field visit.

328 328 151 94 520 144 192 139 77 80

(11,720) (11,720) (5,410) (3,359) (18,570) (5,140) (6,870) (4,969) (2,745) (2,853)
Appendix III 109

G SN transect

Distance from 

beginning of 

transect, in m

Soil moisture observation; water-surface elevation, in m above sea level; or flow observation1

1

 Local time of observation or water-level measurement in brackets.

2/12/97 3/11/97 4/3/97 9/29/97 9/30/97 10/21/97 1/27/98 3/26/98 9/9/98 10/6/98 2/9/99 6/28/99 9/7/99

0 inun sat inun 1.559

[13:30] inun sat sat inun

9 no water

0.824

[16:48] no water no water

0.874

[17:07]

no water

[12:35]

0.844

[15:26]

15.3 sat sat sat sat

33

(tidal creek)

flow in

[16:15]

0.450

[10:56]

flow out

0.368

[16:40]

flow out

0.669

[14:25]

flow out

0.345

[9:43]

0.354

[10:31]

flow out

0.646

[15:15]

flow in

0.342

[12:25]

flow out

0.840

[15:30]

flow out

0.752

[15:12]

flow in

0.663

[14:37]

flow out

0.489

[17:31]

0.336

[14:45]

flow out

0.646

[14:55]

flow out

0.629

[15:12] 

flow out

0.598

[15:30]

flow out

0.351

[17:50]

flow out

38.6 sat

49.2 flow out

[10:50] inun inun sat

62.7 sat sat

88.3 sat sat

Measured stage1 in Sandfly Creek, in m above sea level

0.605

[16:05]

flow in

0.449

[9:40]

flow out

0.303

[16:35]

flow out

0.492

[11:45]

flow in

-0.047

[9:30]

0.141

[10:45]

flow out 0.867

[16:55]

flow out

0.632

[15:07]

flow in

0.946

[17:20]

flow in

0.288

[13:06]

flow in

0.715

[12:30]

flow in

0.834

[15:20]

flow out 0.245

[17:40]

flow out

1.563

[17:26]

-0.087

[14:56]

flow in

Daily high stage in Suwannee River, in m above sea level

0.66 0.85 0.72 0.60 0.62 0.96 1.49 0.88 0.78 0.85

Mean daily flow2 in Suwannee River, in m3/s (ft3/s)

2

 Flow at Branford-Fort White lagged 5 days before date of field visit.

291 503 328 105 105 94 514 1385 144 232 186 77 80

(10,390) (17,970) (11,720) (3,755) (3,745) (3,359) (18,340) (49,460) (5,140) (8,290) (6,660) (2,745) (2,853)
110 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

H SH transect

Distance from 

beginning of 

transect, in m

Soil moisture observation; water-surface elevation, in m above sea level; or flow observation1

1 Local time of observation or water-level measurement in brackets.

3/10/97 3/11/97 4/3/97 9/29/972

2 Additional observations in field notes.

9/30/972 10/21/97 1/27/982 3/26/98 5/13/98 10/6/98 2/9/99 6/28/99 9/7/99

road ~180 m 

east

~1.6

flow west

pond ~30 m 

southeast

0.665

[14:05]

0.674

[17:35]

0.632

[17:00]

0.772

[14:02]

0.758

[11:58] 0.589

[9:55 &

14:36]

0.848

[17:17]

0.778

[10:16] 0.812

[17:36]

0.714

[14:01]

0.699

[13:12]

0.586

0.767 [15:46]

[17:30]

0.752

[17:40]

0.769

[15:51]

tidal creek

~150 m west

inun

[11:50]

inun

[9:45]

flow out

[10:27] inun 

no flow

[13:30]

flow in

sat [15:51]

[14:25]

flow out

[15:59]

0 sat inun sat sat sat sat sat

22.4

(hummock top) dry

28.5 dry dry dry dry dry dry

50 dry dry dry dry dry dry

57.5 sat inun sat inun sat sat sat

86 dry inun dry sat sat sat dry

98 sat inun inun

117.35 inun sat sat sat sat sat

134.2 inun sat inun sat inun inun inun inun inun sat

151 dry sat sat dry dry sat

Measured stage in Gopher River1,3, in m above sea level

3 Not directly related to water levels on this transect except at tidal creek ~150 m west of transect.

0.857

[17:20]

no flow

0.650

[13:18]

flow in

0.702

[16:21]

flow out

0.077

[11:03]

flow out 0.848

[16:50]

flow out

0.375

[12:13]

flow in 0.372

[15:42]

flow out

0.604

[12:03]

flow in

0.818

[16:35]

flow out -0.106

[13:49]

flow in

0.828

[15:57]

 flow in

Daily high stage in Suwannee River at mouth of Sandfly Creek

0.87 0.85 0.72 0.60 0.64 0.62 0.96 1.49 0.81 0.78 0.85

Mean daily flow4, in Suwannee River, in m3/s (ft3/s)

4 Flow at Branford-Fort White lagged 5 days before date of field visit.

495 503 328 105 105 94 514 1385 328 232 186 77 80

(17,670)(17,970)(11,720) (3,755) (3,745) (3,359) (18,340) (49,460) (11,710) (8,290) (6,660) (2,745) (2,853)
Appendix III 111

I BC transect

Distance 

from 

beginning 

of transect, 

in m

Soil moisture observation; water-surface elevation, in m above sea level; or flow observation1

1

 Local time of observation or water-level measurement in brackets.

2/11/97 2/12/97 3/11/97 4/3/97 9/29/97 9/30/97 10/21/97 1/27/98 3/26/98 5/13/98 10/6/98 2/9/99 3/24/99 6/28/99 9/7/99 11/10/99

ditch 2 m 

southeast 

of transect

0.737

[13:45]

0.734

[9:15]

0.691

[17:02]

0.666

[17:10]

0.798

[13:31]

0.782

[13:20]

0.642

[11:35]

0.825

[17:45]

1.319

[11:40] 0.790

[13:16]

0.849

[14:15]

0.737

[15:56]

0.724

[11:04]

0.712

[10:52]

0.673

[16:51]

0.569

4.375 [12:15]

[14:20]

0 dry sat sat dry dry dry dry sat dry

11.9 inun sat

hummock 

tops dry 

23.8 sat sat sat inun sat sat sat sat sat

34.3 inun inun

hummock

tops sat

44.8 sat inun sat sat sat sat sat

66.8 0.728

[15:30]

0.728

[9:35]

and

[14:40]

0.683

[17:08]

0.661

[17:15]

0.805

[13:40]

0.786

[13:37]

and

[14:00]

0.631

[11:47]

0.827

[17:51]

0.800

[14:34]

0.855

[15:07]

0.741

[16:13]

0.731

[11:11]

0.716

[11:10]

0.673

[17:00]

0.567

[12:28]

58.9

low hummocks 

dry

73 inun inun inun sat sat sat sat

88.4 inun

low 

hummocks 

dry 

high 

hummocks 

dry

103.8 inun inun inun sat sat sat

125.6 inun

147.3 sat sat sat at sat sat

168.2 inun

189.1 sat inun sat sat sat sat

202.4

hummocks 

dry

215.61 sat dry dry dry dry dry

Mean daily flow2

 in Suwannee River, in m3/s (ft3/s)

2

 Flow at Branford-Fort White lagged 5 days from date of field visit.

290 291 503 328 105 105 94 514 1385 328 232 186 139 77 80 80

(10,340) (10,390) (17,970) (11,720) (3,755) (3,745) (3,359) (18,340) (49,460) (11,710) (8,290) (6,660) (4,969) (2,745) (2,853) (2,871)
112 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

J LK and DM transects

Transect and

distance from

beginning of transect, 

in m

Soil moisture observation or flow observation1

1

 Local time of observation or water-level measurement in brackets.

11/13/96 12/11/96 4/29/97 4/30/97 1/11/99 6/28/99 9/8/99 10/19/99

LK-0 sat inun sat sat sat sat

LK-3

(hummock top) sat

LK-28.7 sat inun sat sat sat sat

LK-43

(hummock top) sat sat

LK-61 sat inun sat sat inun sat

LK-64

(hummock top) dry sat sat sat

LK-82

(hummock top) sat dry

LK-93.5 sat inun sat sat sat

LK-106

(hummock top) sat

LK-117.4 sat inun sat inun sat

LK-145.5 sat inun sat inun sat

LK-Tidal creek a few 

meters north of end 

of transect

flow out

[~10:00]

no flow

[16:00]

flow out

[~13:30-

14:00]

flow in 

DM-0 sat inun inun sat inun

DM-13.3 sat inun inun sat inun

DM-31.34 sat inun inun sat

DM-53.22 sat inun inun sat inun

Measured stage1 in Suwannee River, in m above sea level

0.137

[13:05]

0.424

[9:40]

No 

water

[~11:20]

0.466

[11:30]

0.448

[10:23]

0.421

[10:56]

0.172

[13:20]

0.161

[16:56]

0.743

[13:26]

0.444

[10:17]

0.392

[17:15]

0.752

[13:34]

Daily high stage in Suwannee River, in m above sea level

0.5 0.72 0.46 0.51 0.75 0.8

Mean daily flow2 in Suwannee River, in m3/s (ft3/s)

2

 Flow at Branford-Fort White lagged 6 days from date of field visit.

190 134 176 171 125 77 80 86

(6,790) (4,770) (6,270) (6,100) (4,482) (2,765) (2,853) (3,054)
Appendix III 113

K Verification plots

Nearest 

transect

Mapped 

forest 

type

RKM Date Percent 

saturated

Percent 

inundated

Mean daily flow1

 in 

Suwannee River

m3

/s ft3/s

CF

O/P 104.4 5/12/98 0 0 313 11,170

104.4 7/8/98 0 0 148 5,300

Rblh3

104.4 5/12/98 0 0 313 11,170

106.7 7/8/98 0 0 148 5,300

94.0 7/9/98 0 0 147 5,250

Rblh2

105.1 5/12/98 100 100 313 11,170

105.1 7/8/98 0 0 148 5,300

106.7 7/8/98 0 0 148 5,300

93.6 7/9/98 0 0 147 5,250

Rblh1 94.1 7/9/98 0 0 147 5,250

Rsw2 93.8 7/9/98 50 27 147 5,250

Rsw1 93.6 7/9/98 60 15 147 5,250

LL

O/P 85.0 7/22/98 0 0 148 5,270

82.5 11/17/98 0 0 176 6,290

Rblh3

85.0 7/22/98 0 0 148 5,270

79.8 7/23/98 0 0 149 5,320

77.6 11/16/98 0 0 179 6,380

82.5 11/17/98 0 0 176 6,290

Rblh2

83.3 7/22/98 0 0 148 5,270

80.1 7/23/98 0 0 149 5,320

79.8 7/23/98 0 0 149 5,320

77.6 11/16/98 0 0 179 6,380

78.4 11/16/98 0 0 179 6,380

82.5 11/17/98 0 0 176 6,290

Rblh1

83.3 7/22/98 62 27 148 5,270

83.3 7/22/98 0 0 148 5,270

79.8 7/23/98 0 0 149 5,320

80.1 7/23/98 0 0 149 5,320

78.4 11/16/98 0 100 179 6,380

82.5 11/17/98 0 0 176 6,290

Rsw2

80.1 7/23/98 100 5 149 5,320

77.6 11/16/98 100 100 179 6,380

82.5 11/17/98 100 100 176 6,290

82.5 11/17/98 100 80 176 6,290

Rsw1

81.1 6/11/98 100 0 187 6,680

82.5 11/17/98 100 95 176 6,290

82.5 11/17/98 100 100 176 6,290

FK

O/P 69.3 9/2/98 0 0 142 5,070

Rblh3 71.1 9/1/98 0 0 144 5,130

70.0 9/2/98 0 0 142 5,070

Rblh2

71.0 9/1/98 0 0 144 5,130

69.3 9/2/98 0 0 142 5,070

70.2 9/2/98 0 0 142 5,070

Rblh1

71.0 9/1/98 100 27 144 5,130

69.5 9/2/98 0 0 142 5,070

69.8 9/2/98 0 0 142 5,070

Rsw2

69.8 9/2/98 100 10 142 5,070

50.5 9/17/98 100 25 176 6,280

48.1 9/18/98 100 60 173 6,190

Rsw1 69.5 9/2/98 100 75 142 5,070

MS

O/P 50.5 9/17/98 0 0 175 6,260

47.9 9/18/98 0 0 176 6,300

Rblh3

51.0 9/17/98 0 0 175 6,260

48.1 9/18/98 0 0 176 6,300

47.8 9/18/98 0 0 176 6,300

Rblh2 50.7 9/17/98 0 0 175 6,260

48.3 9/18/98 100 2 176 6,300

Rblh1

50.5 9/17/98 0 0 175 6,260

48.1 9/18/98 100 2 176 6,300

47.8 9/18/98 100 2 176 6,300
114 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

Nearest 

transect

Mapped 

forest 

type

RKM Date

Local 

time

(at tidal 

plots)

Percent 

saturated

Percent 

inundated

Mean daily flow1

 in 

Suwannee River

m3

/s ft3/s

KN

UTblh

27.7 10/6/98 16:22 100 15 263 9,400

27.7 10/6/98 10:00 100 40 263 9,400

26.2 12/7/98 10:30 0 0 145 5,180

26.4 12/7/98 11:30 0 0 145 5,180

UTmix 36.5 10/5/98 13:55 100 90 224 8,000

27.5 10/6/98 15:16 100 100 263 9,400

UTsw2

36.5 10/5/98 14:43 100 100 224 8,000

27.7 10/6/98 13:57 100 100 263 9,400

26.2 12/7/98 14:00 100 0 145 5,180

UTsw1 27.8 10/6/98 11:48 100 100 263 9,400

26.2 12/7/98 12:30 100 80 145 5,180

Seepage 36.4 10/5/98 15:51 100 75 224 8,000

TK

O/P 23.8 10/27/98 13:00 0 0 375 13,380

UTblh 24.0 10/27/98 15:00 100 0 375 13,380

23.3 12/8/98 15:30 42 0 144 5,150

UTmix

23.8 10/27/98 11:52 100 8 375 13,380

23.0 12/8/98 11:00 100 0 144 5,150

23.0 12/8/98 14:30 54 0 144 5,150

UTsw2

24.0 10/27/98 14:00 100 12 375 13,380

23.0 12/8/98 12:00 100 0 144 5,150

23.0 12/8/98 13:30 100 0 144 5,150

23.7 12/8/98 16:30 100 0 144 5,150

UTsw1 24.0 10/27/98 16:28 100 70 375 13,380

23.3 12/8/98 10:19 100 40 144 5,150

LTham 21.4 10/28/98 9:30 0 0 355 12,680

21.4 10/28/98 12:00 50 0 355 12,680

LTmix 20.0 2/3/99 14:30 0 0 162 5,780

LTsw2 21.2 10/28/98 11:03 100 75 355 12,680

19.8 2/3/99 13:30 100 0 162 5,780

LTsw1

19.3 10/28/98 13:55 100 40 355 12,680

20.1 2/3/99 12:37 100 6 162 5,780

20.0 2/3/99 15:38 100 30 162 5,780

SN 

and 

SH

LTham

13.8 10/28/98 17:00 50 0 375 13,380

13.5 2/4/99 16:00 0 0 162 5,780

13.0 2/25/99 12:15 100 0 178 6,350

LTmix

13.7 10/28/98 15:30 100 0 375 13,380

12.9 2/4/99 15:00 100 40 162 5,780

12.9 2/4/99 10:30 100 4 162 5,780

13.5 2/24/99 11:00 100 0 181 6,470

12.9 2/24/99 14:30 100 3 181 6,470

12.7 2/25/99 11:15 100 0 178 6,350

LTsw2

12.9 2/4/99 13:00 100 70 162 5,780

13.2 2/24/99 13:30 100 8 181 6,470

13.0 2/25/99 10:15 100 70 178 6,350

13.2 2/25/99 14:19 100 16 178 6,350

13.2 2/25/99 15:30 100 1 178 6,350

LTsw1

12.7 2/4/99 11:33 100 80 162 5,780

13.2 2/24/99 15:30 100 4 181 6,470

13.4 2/24/99 12:00 100 5 181 6,470

13.2 2/25/99 16:30 100 15 178 6,350

BC

LTham 11.9 5/13/98 15:00 0 0 337 12,020

LTsw2 11.7 5/13/98 13:30 100 55 337 12,020

LTsw1 12.4 5/13/98 11:40 86 20 337 12,020

1

Flow at Branford-Fort White lagged the appropriate number of days for the nearest transect.

K Verification plots (Continued)
Appendix IV 115

Appendix IV. Salinity of ponds and tidal creeks in the floodplain of the lower Suwannee River, Florida

[Arranged by distance proceeding upstream from mouth of river. Salinities were calculated from field conductivities using the formula: Salinity, in ppt = 

(EC, in mmhos/cm) x .65 (adapted from Hem, 1985). rkm, river kilometers; mmhos/cm, millimhos per centimeter; ppt, parts per thousand]

Waterbody type and location Rkm Date

sampled

EC, in 

mmhos/

cm

Salinity, 

in ppt Antecedent conditions

tidal creek, 40 m north of LK-145 5.1 4/30/97 0.65 0.42 incoming tide

6/28/99 0.43 0.28 incoming tide 

Gopher River, 4 km upstream of mouth 9.2 2/12/97 0.31 0.20 outgoing tide

3/11/97 0.14 0.09 slackwater at high tide

isolated borrow ditch in LTmix forest 

 near BC-0

11.3 3/10/97 3.90 2.53 4.2 cm rain since 2/1/97

3/11/97 4.62 3.00 4.2 cm rain since 2/1/97

9/30/97 2.15 1.40 11.2 cm rain in last 2 weeks

10/21/97 2.17 1.41 .5 cm rain in last 2 weeks

3/26/98 0.08 0.05 major flood, connected and flowing

5/13/98 0.76 0.50 1 1/2 months after major flood

2/9/99 2.92 1.90

storm surge in Sept 1998,

.8 cm rain in last 2 weeks

3/24/99 2.42 1.57 3.9 cm rain since 3/1/99

6/28/99 3.52 2.29 generally dry, 8.8 cm rain in last 2 weeks

9/7/99 2.73 1.77 .9 cm rain in last 2 weeks

11/10/99 1.97 1.28 6.3 cm rain since 10/1/99

isolated pond in LTsw1 forest near

 BC-67

11.3 2/12/97 8.02 5.21 .3 cm rain in last 2 weeks

3/11/97 7.03 4.57 4.2 cm rain since 2/1/97

9/30/97 2.23 1.45 11.2 cm rain in last 2 weeks

10/21/97 4.10 2.67 .5 cm rain in last 2 weeks

5/13/98 0.66 0.43 after major flood in March

2/9/99 3.21 2.09

storm surge in Sept 1998,

.8 cm rain in last 2 weeks

3/24/99 2.08 1.35 3.9 cm rain since 3/1/99

6/28/99 4.44 2.89 generally dry, 8.8 cm rain in last 2 weeks

9/7/99 3.51 2.28 .9 cm rain in last 2 weeks

11/10/99 3.48 2.26 6.3 cm rain since 10/1/99

isolated borrow pit 366 m north of BC 11.4 10/21/97 3.42 2.22 .5 cm rain in last 2 weeks

semi(?)-isolated pond in LTsw2 forest at V4-12 11.7 2/9/99 0.37 0.24 .8 cm rain in last 2 weeks

isolated pond in LTsw1 forest at V4-10 12.4 5/13/98 0.30 0.20 after major flood in March

2/9/99 0.96 0.62 .8 cm rain in last 2 weeks

isolated borrow pit 550 m south of SH 12.6 4/3/97 0.18 0.11 2.3 cm rain in last 2 weeks

isolated pond near SH-0 12.6 3/11/97 2.14 1.39 4.2 cm rain since 2/1/97

9/30/97 1.59 1.03 11.2 cm rain in last 2 weeks

10/21/97 2.69 1.75 .5 cm rain in last 2 weeks

5/13/98 0.41 0.26 after major flood in March

2/9/99 2.00 1.30

storm surge in Sept 1998,

.8 cm rain in last 2 weeks

6/28/99 2.89 1.88 generally dry, 8.8 cm rain in last 2 weeks

9/7/99 2.84 1.85 .9 cm rain in last 2 weeks

semi-isolated pond in LTsw2 forest, 

 150 m west of SH-0

12.6 5/13/98 0.31 0.20 after major flood in March

Sandfly Creek 1.5 km upstream of mouth 12.9 3/11/97 0.21 0.14 outgoing tide

tidal creek in LTmix forest near SN-34 13.0 3/11/97 0.17 0.11 incoming tide

9/30/97 0.50 0.33 outgoing tide

2/9/99 0.67 0.43 outgoing tide

isolated pond in LTsw2 forest at V4-24 13.2 10/20/97 0.38 0.25 .5 cm rain in last 2 weeks

semi(?)-isolated pond in LTsw1 forest at OS4-19 13.4 10/20/97 0.71 0.46 .5 cm rain in last 2 weeks

tidal creek at TK-292 19.8 4/3/97 0.21 0.13 slackwater at high tide

semi-isolated pond in LTsw1 forest near TK-95 19.8 4/2/97 0.26 0.17 4.2 cm rain since 3/1/97

3/24/99 0.31 0.20 3.9 cm rain since 3/1/99

6/28/99 0.26 0.17 generally dry, 8.8 cm in last 2 weeks

9/7/99 0.32 0.21 .9 cm rain in last 2 weeks

isolated borrow ditch in UTsw1 forest,

 490 m northwest of KN-729

31.2 6/3/97 0.31 0.20 8.6 cm rain in last 2 weeks

semi-isolated pond at KN-662 31.2 6/3/97 0.20 0.13 8.6 cm rain in last 2 weeks
116 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

Appendix V. Soil profile descriptions for floodplain forest types of the lower Suwannee River, Florida.

[Within each forest type, profiles are arranged by decreasing distance from the river mouth. Numbers in profile names indicate distance from beginning of 

transect, except for OS4-BC, which is an observation site, and V4-12 and V4-10 which are verification plots. Matrix colors are given in Munsell notation with 

designations for hue, value, and chroma. rkm, river kilometer; cm, centimeters; %, percent]

Other abbreviations used in profile descriptions:

Texture: Structure: Mottles:

C clay FGR fine granular Mottles are described in this order:

COS coarse sand FSBK fine subangular blocky 1. Quantity:

FS fine sand G granular f few

FSL fine sandy loam M massive c common

LCOS loamy coarse sand MSBK massive subangular blocky m many

Limerock limerock SBK subangular blocky 2. Size:

LS loamy sand SG single grain 1 fine

MK muck 2 medium

MKC mucky clay 3 coarse

MKFS mucky fine sand 3. Contrast:

MKL mucky loam f faint

MKPT mucky peat d distinct

MKS mucky sand p prominent

MKSL mucky sandy loam

S sand 

SCL sandy clay loam

SiC silty clay

SiL silty loam

SL sandy loam

VFS very fine sand

Profile 

name 

Distance 

from river 

mouth, in 

rkm

Horizon

Thickness, in 

cm

Matrix color Texture Structure Mottles and other features

Oak/pine

CF-1066 104.4

A 5.0 10YR 6/1 FS G

E1 55.0 10YR 7/2 FS G f1p 7.5YR 6/8

E2 15.0 10YR 5/3 FS G c1d 10YR 6/6

E3 47.0 10YR 7/2 FS G

Bt1 32.0 n/a SL SBK 10YR 6/1,7/1,5/6

Rblh3

CF-144 104.4

A 10.0 10YR 5/2 VFS G

E1 20.0 10YR 5/3 VFS G

E2 20.0 10YR 7/4 VFS G m1p 10YR 4/6, 0.5 cm Fe masses

E3 63.0 10YR 7/2 VFS G 1cm Fe masses

Bt1 42.0 n/a SL SBK 10YR 4/6,5/8,6/4

LL-707 77.7

A 12.0 10YR4/2 S G

C1 25.0 10YR 5/2 S SG

C2 73.0 10YR 6/4,5/4 S

C3 33.0 10YR 7/3 S

C4 57.0 10YR 6/6 S c1d 7.5YR 5/8

LL-732 77.7

A 7.0 10YR 5/2 S SG

A2 20.0 10YR 5/3 S SG

C1 58.0 10YR 4/4 S G

C2 78.0 10YR 7/6 S with pockets uncoated grains

C3 37.0 10YR 6/6 S G c3d 10YR 4/6 SL

MS-173 42.5

A 7.0 10YR 5/1 S G

E 38.0 10YR 6/2 S SG 10YR 4/3

E1 30.0 10YR 7/2 S G

Bh 10.0 10YR 3/2 FS FSBK weakly cemented

Bw1 13.0 10YR 5/6 S SG few 7.5YR 6/6

Bw2 27.0 10YR 5/4 S SG common 10YR 5/6

Btg 50.0 10YR 4/1 SCL SBK c3p 10R 4/6

Rblh2

CF-10 104.4

A 12.0 10YR 3/2 VFS G

E1 30.0 10YR 5/3 VFS G

E2 20.0 10YR 7/2 VFS G m2d 10YR 4/4

Bt1 20.0 10YR 5/2 SL SBK c2p 7.5YR 5/6

C1 47.0 10YR 6/2 VFS G 10YR 8/2

CF-25 104.4

A 7.0 10YR 3/2 C M

Bt1 30.0 10YR 4/2 SCL SBK m1d 10YR 4/4

C1 62.0 2.5Y 5/1 C M m1f 2.5Y 6/4

C2 55.0 2.5Y 6/2 C M c2f 2.5Y 5/1
Appendix IV 117

CF-94 104.4

A 15.0 10YR 4/1 VFS G

C1 25.0 10YR 6/2 VFS G

C2 22.0 10YR 5/3 VFS G 10YR 4/6 masses

C3 27.0 10YR 5/6 VFS G

C4 65.0 2.5Y 8/4 VFS G

LL-548 77.7

A 7.0 10YR 3/1 C M

B1 23.0 10YR 7/2 S SG

B2 25.0 10YR 5/2 SCL m1p 7.5YR 4/4

B3 32.0 SL 10YR 6/1,6/6,5/8

B4 63.0 10YR 5/1 SCL c2p 5YR 4/6, 10YR 5/8

Cg 50.0 10YR 6/1 LCOS SG

LL-783 77.7

A 7.0 10YR 4/2 S G

E1 58.0 10YR 5/3 LS c1d 10YR 4/4

E2 30.0 10YR 7/2 S SG

Bt1 63.0 10YR 5/4 SCL MSBK c2p 7.5 YR 5/6; c2f 10YR 6/3, 2.5YR 5/6

C1 42.0 10YR 5/6 S SG

FK-9 64.5

A 5.0 10YR 6/2 FS SG +5 cm overburden

A2 12.0 10YR 4/2 FS SG

C1 30.0 10YR 5/3 FS SG

C2 38.0 10YR 5/3 FS G 10YR 6/4,6/2

C3 25.0 10YR 6/2 FS SBK c1d 10YR 6/4

MS-887 42.5

A 5.0 10YR 3/1 LS G 

A2 5.0 10YR 4/2 LS G c1d 10YR 6/2,5/4

C1 20.0 10YR 6/2 VFS G m1d 10YR 5/4

C2 45.0 10YR 7/2 VFS SBK c2p 10YR 5/6, concretions

C3 87.0 10YR 7/2 FS SG m1d 10YR 6/4

Rblh1

CF-169 104.4

A 12.0 10YR 4/1 FS G

E1 47.0 10YR 6/2 FS G

E2 27.0 10YR 7/3 FS G m1f 10YR 7/4

E3 22.0 10YR 7/2 FS G

E4 35.0 10YR 5/2 FS G c1p 10YR 4/6

Bt1 10.0 10YR 5/2 SL G c2p 10YR 4/6, 10 YR 8/1 S

CF-303 104.4

A 10.0 10YR 2/2 MKFS G

C1 32.5 10YR 6/2 S SG

C2 45.0 10YR 7/2 S SG

C3 67.5 10YR 4/3 S G

CF-1088 104.4

A 10.0 10YR 4/1 MKFS G

C1 40.0 10YR 7/2 FS SG

C2 62.0 10YR 5/3 FS G

C3 42.0 10YR 7/2 FS G

LL-0 77.7

A 10.0 10YR 2/2 C M

B1 43.0 7.5YR 3/1 C M c1p 7.5YR 4/6

B2 22.0 10YR 6/2 C M c1p 5YR 4/6

B3 25.0 10YR 5/2 SCL FSBK

B4 32.0 LS FGR 10YR 6/2, 6/6, 5YR 5/8

B5 25.0 10YR 5/1 SCL FSBK c2p 10YR 6/6

B6 43.0 C M 10YR 6/1, 5/6, 5YR 4/6

LL-246 77.7

A 12.0 10YR 3/1 C M

B1 63.0 10YR 3/1 C M f1p 7.5YR 5/6

B2 62.0 10YR 4/1 SL

B3 38.0 10YR 5/1 SCL 10YR 5/1, 3/1

LL-271 77.7

A 5.0 10YR 3/2 C M

A2 20.0 10YR 3/1 C

B1 30.0 10YR 4/1 C M

B2 32.0 10YR 5/1 SCL

B3 25.0 10YR 6/2 LS c2p 10YR 5/6, 6/6

B4 63.0 10YR 5/1 SCL c3d 10YR 5/6, 6/6; c2p 5YR 4/6

LL-468 77.7

A 10.0 10YR 3/2 C M

E1 25.0 10YR 6/2 LS

Bt1 117.0 10YR 5/1, 5/2 SCL FSBK c3d 10YR 5/4, 6/6; c3p 5YR 4/8

Cg 48.0 10YR 5/4 LCOS SG f3d 10YR 5/2

Profile 

name 

Distance 

from river 

mouth, in 

rkm

Horizon

Thickness, in 

cm

Matrix color Texture Structure Mottles and other features
118 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

LL-917 77.7 A 5.0 10YR 3/1 C M

B1 195.0 10YR 4/1 C M c1p 2.5YR 4/6

FK-40 64.5

A 7.0 10YR 3/2 SiL M

E 23.0 10YR 7/2 FS G

Bt1 7.0 10YR 5/2 FSL SBK

Bt2 73.0 10YR 6/1 SCL SBK c2p 10YR 5/6

Bt3 40.0 10YR 5/1 SCL SBK c2p 10YR 5/6, CaCo3 nodules

BC 50.0 10YR 5/2 FSL G c2p 10YR 5/6

FK-957 64.5

A 10.0 10YR 3/1 MKL M

Cg1 90.0 10YR 6/2 S SG

Cg2 25.0 10YR 5/2 S SG

MS-42 42.5 A 25.0 10YR 3/1 MKS G

C1 100.0 10YR 6/2 S SG

MS-939 42.5 A 5.0 10YR 3/1 C M

C1 50.0 5GY 4/1 C M 7.5YR 5/6, pore linings

MS-962 42.5 31.0 5GY 4/1 C 7.5YR 5/6, stains

MS-1005 42.5

A 2.0 10YR 7/3 VFS SG

A2 8.0 10YR 4/2 VFS SG c1p10YR 5/6, pore linings

C1 10.0 10YR 7/2 VFS SG m1p 10YR 6/6, c2d 10YR 4/2

C2 7.0 10YR 5/1 SL G m2d 10YR 4/4, pore linings

C3 33.0 10YR 6/1 LS G c2d 10YR 3/2

C4 65.0 10YR 5/1 SL SBK m2p 7.5YR 4/6

IIC 60.0 5GY 4/1 C M f1p 10YR 4/6; f1d 2.5Y 3/4

Rsw2

CF-47 104.4

A 7.0 10YR 3/1 C M

Bt1 22.0 10YR 4/1 C SBK pore linings

Bt2 65.0 10YR 5/1 C SBK m2d 10YR 5/6

C1 60.0 2.5Y 5/1 C M m2d 2.5Y 5/4, 5BG 5/2, drier

CF-1108 104.4

A 12.0 10YR 2/1 C M

Bt1 17.0 10YR 3/1 C SBK clay bridging

Bt2 45.0 10YR 5/1 C SBK c3p 10YR 6/6, clay bridging

C1 50.0 10YR 6/1 C M m3d 10YR 7/6

CF-1191 104.4

A 10.0 10YR 2/2 MKFS G

E1 5.0 10YR 5/2 FS G

E2 10.0 10YR 5/3 FS G

E3 42.0 10YR 5/2 FS G

Bt1 45.0 10YR 6/1 SCL SBK

Bt2 45.0 10YR 6/2 SL SBK

LL-192 77.7

A 20.0 10YR 3/1 C M

B1 40.0 10YR 4/1 C M

B2 17.0 10YR 4/1 SCL M f1p 7.5YR 5/6

Cg 73.0 10YR 6/1 S SG

LL-389 77.7 A 25.0 10YR 3/1 C M

B1 50.0 10YR 6/1 S SG

LL-400 77.7

A 7.0 10YR 3/2 C M

B1 28.0 10YR 5/2 S SG

B2 40.0 10YR 2/1 C

B3 20.0 10YR 6/1 S

LL-588 77.7

A 12.0 10YR 3/2 C M

C1 18.0 10YR 6/1 S SG

Cg 170.0 10YR 6/2 COS f1d 10YR 5/4

FK-72 64.5

A 15.0 10YR 3/2 SiC M

Bt1 25.0 10YR 5/1 SCL SBK f1d 7.5YR 4/4

Bt2 37.0 7.5YR 6/1 FSL SBK c2p 10YR 5/6

FK-107 64.5

A 12.0 10YR 3/1 SiC M m1d 10yr 3/4

Bt1 53.0 10YR 5/2 SCL SBK m2d 10YR 3/4

Bt2 25.0 10YR 6/2 FSL SBK f2f 10YR 5/3

FK-166 64.5

A 10.0 10YR 3/2 SiC M

C1 35.0 10YR 4/1 C M c2p 10YR 4/6

C2 70.0 10YR 5/1 SCL SBK c2d 10YR 5/4

Profile 

name 

Distance 

from river 

mouth, in 

rkm

Horizon

Thickness, in 

cm

Matrix color Texture Structure Mottles and other features
Appendix IV 119

FK-210 64.5

Oa 45.0 10YR 2/2 MK M

C1 10.0 10YR 3/1 SCL G

C2 20.0 10YR 4/1 C M

Rsw1

CF-211 104.4

A 10.0 10YR 3/1 SCL M

A2 30.0 10YR 4/1 SL M

C1 90.0 10YR 6/2 S G

CF-236 104.4 A 10.0 10YR 3/1 C M

C1 30.0 10YR 6/2 S SG

CF-261 104.4 A 25.0 10YR 3/1 C M

C1 95.0 10YR 6/2 S SG

CF-286 104.4 A 10.0 10YR 3/1 FS G

C1 65.0 10YR 6/2 S SG

CF-1143 104.4

Oa 15.0 10YR 2/1 MK M

A 30.0 10YR 5/2 S G

C1 15.0 10YR 6/2 S SG

C2 27.0 2.5Y 5/2 SCL M coarse 10YR 5/2

C3 37.0 2.5Y 5/2 LS G

CF-1153 104.4

A 20.0 10YR 2/1 C M

C1 30.0 10YR 4/1 C M

C2 75.0 5GY 6/2 C M 10YR 4/1 streaks; 7.5YR 5/6 stains

FK-795 64.5 Oa 150.0 10YR 2/2 MK M

Cg1 30.0 10YR 6/2 S SG

FK-855 64.5 Oa 117.0 10YR 2/2 MK M

Cg1 63.0 10YR 6/2 S SG

FK-888 64.5 Oa 117.0 10YR 2/2 MK M

Cg1 63.0 10YR 6/2 S SG

FK-909 64.5

Oa 50.0 10YR 2/2 MK M

C1 12.0 10YR 3/1 SCL M

C2 26.0 10YR 5/2 LS G

C3 37.0 10YR 7/1 S G

FK-937 64.5

Oa 12.0 10YR 2/2 MK M

C1 8.0 10YR 4/1 SCL M

C2 92.0 10YR 7/2 S SG

UTblh

KI-56 31.2

C 12.0 10YR 3/2 S G

Cg1 50.0 10YR 6/2 S SG

Cg2 65.0 10YR 5/3 S SG

Cg3 73.0 10YR 7/2 S SG

UTmix

KN-0 31.2

C 15.0 10YR 3/1 FSL M

Cg1 160.0 10YR 3/2 C M

Cg2 25.0 10YR 5/2 S SG

KN-729 31.2

Oa 5.0 10YR 2/1 MK M

C 5.0 10YR 3/1 MKL M

Cg1 15.0 10YR 4/2 LS G

Cg2 37.0 10YR 6/1 S SG

Cg3 26.0 10YR 8/1 S SG

Cg4 37.0 10YR 5/3 S SG

UTsw2

MS-623 42.5

A 15.0 10YR 3/1 SCL M

C 37.0 10YR 5/2 SL G

Cg1 38.0 10YR 6/1 LS SG c3f 2.5Y 5/3

Cg2 92.0 10YR 6/4 S

MS-774 42.5

A 12.0 10YR 2/1 SCL M

C1 40.0 10YR 3/1 SCL M

C2 18.0 2.5Y 5/6,4/6 LS G 10YR 4/1, stratified

KN-50 31.2

Oa 31.0 10YR 3/2 MK M

Cg1 37.0 10YR 4/2 MKC M

Cg2 132.0 10YR 3/2 MKC M

Profile 

name 

Distance 

from river 

mouth, in 

rkm

Horizon

Thickness, in 

cm

Matrix color Texture Structure Mottles and other features
120 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

UTsw1

MS-250 42.5 Oa 20.0 10YR 3/1 MK M

C1 135.0 10YR 3/1 C M

MS-405 42.5 Oa 30.0 10YR 2/2 MK M

C1 60.0 10YR 3/2 MKC M

KN-122 31.2

Oa 40.0 10YR 3/2 MK M

Cg1 80.0 10YR 5/2 MKC M

Cg2 12.0 10YR 6/2 S SG

KN-199 31.2

Oa 50.0 10YR 3/2 MK M

Cg1 25.0 10YR 3/1 C M

Cg2 125.0 10YR 3/2 MK M

KN-532 31.2 Oa 55.0 10YR 2/2 MK M

Cg1 145.0 10YR 3/1 SCL M

KN-632 31.2

Oa 30.0 10YR 2/2 MK M

C 45.0 10YR 3/2 SCL M

Cg1 37.0 10YR 4/3 SL G

Cg2 50.0 10YR 6/2 S G

Cg3 38.0 10YR 6/1 SCL

LTham

SH-0 13

Oa1 20.0 10YR 2/1 MK M

C1 17.0 10YR 4/2 S SG

C2 63.0 10YR 5/6 S G

SH-40 13

Oa1 5.0 10YR 2/2 MK M

A 10.0 10YR 2/1 MKFS G

E 40.0 10YR 5/2 S G

Bh1 15.0 10YR 2/2 LS SBK

Bh2 30.0 7.5YR 2/3 LS SBK

Bw 50.0 10YR 5/4 S G

SH-65 13

Oa1 7.0 10YR 2/1, 2/2 MK M

C1 30.0 10YR 6/2 S SG

C2 25.0 10YR 4/1 S G

C3 28.0 10YR 4/3 S G

C4 10.0 10YR 3/2 S G

SH-99 13

Oa1 12.0 7.5YR 2.5/2 MK M

E 43.0 10YR 3/1 S G

Bh1 45.0 10YR 2/2 FS SBK

OS4-BC 11.2 15.2 10YR 5/1 SCL

25.4 2.5Y 5/6 LS

LTmix

SN-17 13

Oa1 12.0 10YR 3/1 MK M

Oa2 65.0 7.5YR 2.5/2 MK M

C1 73.0 10YR 4/2 S SG f1f 10Y 5/1

SN-34 13.0 A 15.0 10YR 3/2 S G

C1 80.0 10YR 5/2 S SG 10YR 3/1

SN-52 13.0

Oa1 12.0 10YR 2/1 MK M

Oa2 33.0 7.5YR 2/2 MK M

C1 67.0 7.5YR 2.5/2 S SG

SN-77 13.0

Oa1 5.0 10YR 2/1 MK M

Oa2 40.0 7.5YR 2.5/2 MK M

C1 35.0 10YR 4/2 S SG m2d 10YR 6/2

C2 45.0 2.5Y 4/2 S SG

BC-139 11.2

Oa1 20.0 10YR 2/1 MK M

A 40.0 10YR 2/1 MKSL M

C1 15.0 10YR 3/1 SCL M high % of organic matter

C2 32.0 2.5Y 5/6 LS G

LK-0 5.2 Oa1 55.0 10YR 2/1 MK M

Oa2 145.0 10YR 2/2 MK M

LK-29 5.2 Oa1 10.0 10YR 2/1 MK M

Oa2 165.0 10YR 2/2 MK M

LK-64 5.2

Oa1 37.0 10YR 2/2 MK M 50% live roots

Oa2 48.0 10YR 2/2 MK M 90% roots & wood fragments

Oa3 115.0 10YR 2/2 MK M 50-70% fiber, unrubbed

Profile 

name 

Distance 

from river 

mouth, in 

rkm

Horizon

Thickness, in 

cm

Matrix color Texture Structure Mottles and other features
Appendix IV 121

LK-68 5.2 Oa1 15.0 10YR 2/1 MK M 15% live roots

Oa2 185.0 10YR 2/2 MK M 15% live roots

LK-100 5.2 Oa1 7.0 10YR 2/2 MK M

Oa2 193.0 10YR 2/2 MK M

LTsw2

TK-30 19.9

Oa1 100.0 10YR 2/2 MK M common live roots

C1 20.0 10YR 4/2 S G

C2 55.0 10YR 6/2 S G 10YR 6/4 with 10YR 2/1 strata

TK-206 19.9 Oa1 200.0 10YR 2/2 MK M

TK-292 19.9 Oa1 200.0 10YR 2/2 MK M

TK-333 19.9 Oa1 13.0 10YR 2/1 MK M hummock with 80% live roots

V4-12 11.7

38.0 10YR 2/1 MK

43.0 2.5Y 7/2 SCL f1p 5 YR 4/6 

10.0 2.5Y 5/6 LS

BC-196 11.2

38.0 10YR 2/1 MKPT

115.0 10YR 3/1 MKL

77.0 10YR 5/6 LS

BC-206 11.2

Oa1 10.0 10YR 3/1 MKPT M

Oa2 32.0 10YR 2/2 MK M

Oa3 10.0 10YR 2/1 MK M

C1 70.0 2.5Y 4/3 SCL M

C2 13.0 2.5Y 7/3 SL G m1 CaCo3

DM-7 4.8 Oa1 242.0 10YR 2/2 MK M sand at 2.46 m

LTsw1

TK-48 19.9 Oa1 40.0 10YR 2/1 MK M 50-90% fine live roots

Oa2 55.0 10YR 2/2 MK M

TK-95 19.9 Oa1 175.0 10YR 2/2 MK M

TK-117 19.9 Oa1 200.0 10YR 2/2 MK M

TK-175 19.9 15.0 10YR 2/1 MK hummock with 25% live roots

TK-392 19.9 Oa1 21.0 10YR 2/2 MK M

TK-412 19.9

A 25.0 10YR 2/1 SiL M m1p 10YR 4/6

C1 65.0 10YR 4/1,5/1 C M m1p 5YR 4/4

C2 15.0 10YR 3/1 C M 15-25% fine roots

C3 95.0 10YR 2/2 MKC M

V4-10 12.4

55.8 10YR 2/1 MK

22.8 10YR 3/2 FSL

5.0 Limerock

BC-31 11.2

Oa1 25.0 10YR 2/2 MK M

Oa2 30.0 10YR 3/2 MK M

C1 15.0 10YR 3/2 MKL M

C2 55.0 2.5Y 5/6 LS G

BC-67 11.2

A 30.0 10YR 3/1 MKL M

C1 60.0 2.5Y 4/4 SL G

C2 38.0 2.5Y 5/6 LS G

BC-68 11.2

15.2 10YR 2/2 MK

30.5 10YR 3/2 MK

30.5 10YR 3/1 MKL

38.0 2.5Y 5/6 LS

38.0 2.5 Y5/6 FSL

LK-131 5.2 Oa1 25.0 10YR 2/2 MK M 50% live roots

Oa2 175.0 10YR 2/2 MK M

DM-31 4.8 Oa1 250.0 10YR 2/2 MK M sand at 2.54 m

Oa1 262.0 10YR 2/2 MK M sand at 2.67 m

Profile 

name 

Distance 

from river 

mouth, in 

rkm

Horizon

Thickness, in 

cm

Matrix color Texture Structure Mottles and other features
122 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

0

102030405060708090

100

0 100 200 300 400 500 600 700 

FLOW, IN CUBIC METERS PER SECOND

0 5,000 10,000 15,000 20,000 25,000 

FLOW, IN CUBIC FEET PER SECOND

Inu

INUNDATED AREA, IN PERCENT OF TOTAL AREA

OF FOREST TYPE ON TRANSECT

CLL MA

CF Rblh2LL Rblh2FK Rblh2MS Rblh2Average Rblh2

CF Rblh1LL Rblh1FK Rblh1MS Rblh1Average Rblh1

CF Rsw2LL Rsw2FK Rsw2Average Rsw2

CF Rsw1LL Rsw1FK Rsw1Average Rsw1

EXPLANATION

Appendix VI. Percentage of inundated and saturated area for each forest type and transect in the riverine reach in relation to flow in 

Florida. Flow is combined flow of Suwannee River at Branford and Santa Fe River near Fort White. All riverine verification plot data 

verification plot were combined with data for the transect closest to it.)
Appendix IV 123

0

102030405060708090

100

0 100 200 300 400 500 600 700 

FLOW, IN CUBIC METERS PER SECOND

0 5,000 10,000 15,000 20,000 25,000 

FLOW, IN CUBIC FEET PER SECOND

Satu

SATURATED AREA, IN PERCENT OF TOTAL AREA

OF FOREST TYPE ON TRANSECT

CF LL MS Ave

CF Rblh2LL Rblh2FK Rblh2MS Rblh2Average Rblh2

CF Rblh1LL Rblh1FK Rblh1MS Rblh1Average Rblh1

CF Rsw2LL Rsw2FK Rsw2Average Rsw2

CF Rsw1LL Rsw1FK Rsw1Average Rsw1

EXPLANATION

Appendix VI. Percentage of inundated and saturated area for each forest type and transect in the riverine reach in relation to flow in 

Florida. Flow is combined flow of Suwannee River at Branford and Santa Fe River near Fort White. All riverine verification plot data a

verification plot were combined with data for the transect closest to it.) (Continued)
124 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 

Impacts of Flow Reductions

EXISTING DURATION CURVE

-2.8 (-100)

-8.4 (-300)

-14 (-500)

-28 (-1,000)

-56 (-2,000)

DURATION CURVES FOR HYPOTHETICAL

FLOW REDUCTIONS-In cubic meters per

second (cubic feet per second)

0

100

200

300

400

500

600

700

FLOW, IN CUBIC METERS PER SECOND

FLOW, IN CUBIC FEET PER SECOND

0

5,000

10,000

15,000

20,000

PERCENT OF TIME FLOW IS EQUALED OR EXCEEDED

0 10 20 30 40 50 60 70 80 90 100

Appendix VII. Flow duration curves for five hypothetical flow reductions compared to the existing flow duration curve 

for flows up to 700 cubic meters per second (24,720 cubic feet per second) in the lower Suwannee River, Florida. 

Flow durations were based on Branford-Fort White flows (1933-99).