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 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 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¢ 19.2š and longitude 83× 9¢ 51.8š. 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.) 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 Hydrology, Vegetation, and Soils of Riverine and Tidal Floodplain Forests of the Lower Suwannee River, Florida, and Potential Impacts of Flow Reductions