Prepared in cooperation with the
SUWANNEE RIVER WATER MANAGEMENT DISTRICT
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
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 Districts 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 long-term 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 ground-water 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.

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
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
        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
        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
        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



CONVERSION FACTORS, DATUMS, AND UNIT ABBREVIATIONS

                             Multiply   By      To obtain
                
centimeter (cm)         0.3937  inch
meter (m)               3.28    foot
kilometer (km)          0.62    mile
river kilometers (rkm)          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)

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
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
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 pr2, in which p= 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.)
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. 
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.
                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.     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
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.      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.) LHer. 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



Hydrology, Vegetation, and Soils of Riverine 
and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential 
Impacts of Flow Reductions