Bathymetry and Vegetation in Isolated 

Marsh and Cypress Wetlands in the 

Northern Tampa Bay Area, 2000-2004

By Kim H. Haag, Terrie M. Lee, and Donald C. Herndon 

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with

Pinellas County, Southwest Florida Water Management District, and

Tampa Bay Water

Scientific Investigations Report 2005-5109
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2005

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Suggested Citation: Haag, K.H., Lee, T.M., and Herndon, D.C., 2005, Bathymetry and Vegetation in Isolated Marsh and 

Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004: U.S. Geological Survey Scientific Investigations Report 

2005-5109, 49 p.
 iii

Contents

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

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

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

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Site Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Description of the Study Area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Acknowledgments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Methods of Data Collection and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Delineation of the Wetland Perimeter and Determination of Perimeter Elevations. . . . . . . . . . . . . . . . . . . . . . 7

Measurement of Wetland Stage and Collection of Bathymetric Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Creation of Bathymetric Contour Maps and Calculation of Wetland Area and Stored Water Volume . . . . . . . 10

Assessment of Wetland Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

Bathymetry of Marsh and Cypress Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Stage-Area-Volume Relations for Marsh and Cypress Wetlands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Potential Effects of Bathymetric Mapping Approach on Stage-Area and Stage-Volume Relations. . . . . . . . . . . 17

Relative Abundance of Wetland Plants in Fixed Plots . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Natural Marsh Wetlands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

 Impaired Marsh Wetland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

 Augmented Marsh Wetlands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

 Natural Cypress Wetlands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

 Impaired Cypress Wetland. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

 Augmented Cypress Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Relation of Wetland Vegetation to Bathymetry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Appendixes

1. Comprehensive list of wetland staff gages and offsets to NGVD of 1929 . . . . . . . . . . . . . . 40

2-11. Estimated area and volume of water corresponding to stage and depth below land 

surface elevation at palmetto fringe in:

2. Duck Pond Marsh. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

3. Green Swamp Cypress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

4. Green Swamp Marsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

5. Hillsborough River State Park Marsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

6. S-63 Cypress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

7. S-68 Cypress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

8. W-03 Marsh. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

9. W-05 Cypress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

10. W-19 Cypress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

11. W-29 Marsh. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

12. Names and status of wetland plants identified in fixed plots at wetland sites . . . . . . . . . 46

13. Comparison of National Wetlands Inventory and U.S. Geological Survey wetland

area estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
iv 

Figures

1. Map showing location of study wetlands in the northern Tampa Bay area, west-central Florida . . . . . . . 6

2-11. Figures showing wetland bathymetric contours, density of bathymetric data points, and

stage-volume and stage-area curves for:

2. Duck Pond Marsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3. Green Swamp Cypress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

4. Green Swamp Marsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

5. Hillsborough River State Park Marsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

6. S-63 Cypress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

7. S-68 Cypress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

8. W-03 Marsh. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

9. W-05 Cypress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

10. W-19 Cypress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

11. W-29 Marsh. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

12-13. Maps showing contour lines developed for:

12. W-29 Marsh from all bathymetric data points, a subset of bathymetric data points 

along three transect lines, and a subset of bathymetric data points along three 

transect lines and a contour line.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

13. Green Swamp Marsh from all bathymetric data points, a subset of bathymetric 

data points along two transect lines, and a subset of bathymetric data points along 

two transect lines and a contour line. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

14-16. Graphs showing:

14. Effects of a reduced density of bathymetric data points at W-29 Marsh on stage-area 

and stage- volume relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

15. Effects of a reduced density of bathymetric data points at Green Swamp Marsh on 

stage-area and stage-volume relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

16. Changes in weekly average flooded area over time at Green Swamp Marsh and 

W-29 Marsh. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

17. Map showing distribution and status of Pinus elliotii trees in W-29 Marsh during 

January-February, 2004. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

18-19. Graphs showing:

18. Inundated area at an impaired marsh and a natural marsh during an average year

and a wet year. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

19. Duration of inundation of vegetation plots at an impaired marsh and a natural marsh 

during an average year and a wet year . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
 v

Tables

1. Names, locations, and physical characteristics of study wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

2. Indicators of normal pool elevation and elevation of palmetto fringe at wetland edge . . . . . . . . . . . . . . .8

3. Benchmark names, USGS elevations, and offsets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

4. Vegetation in fixed plots in Green Swamp Marsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

5. Vegetation in fixed plots in Hillsborough River State Park Marsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

6. Vegetation in fixed plots in W-29 Marsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

7. Vegetation in fixed plots in W-03 Marsh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

8. Vegetation in fixed plots in Duck Pond Marsh. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

9. Vegetation in fixed plots in Green Swamp Cypress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

10. Vegetation in fixed plots in S-68 Cypress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

11. Vegetation in fixed plots in W-19 Cypress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

12. Vegetation in fixed plots in S-63 Cypress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

13. Vegetation in fixed plots in W-05 Cypress. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

14. Elevation of vegetation plots and percent of wetland area inundated at specified elevations . . . . . . 33

Conversion Factors and Datum

Multiply By To obtain

Length

acre-foot (acre-ft) 1,233 cubic meter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

million gallons per day (Mgal/d) 0.04381 cubic meter per second

Area

acre 0.4047 hectare

square foot (ft2) 0.09290 square meter

square mile (mi2) 2.590 square kilometer

s

Vertical coordinate information is referenced to the “National Geodetic Vertical Datum of 1929 

(NGVD of 1929).”

Horizontal coordinate information is referenced to the “North American Datum of 1927 (NAD 27).”
CBR Cross Bar Ranch Well Field

CCW Cypress Creek Well Field

DBH diameter at breast height

FDEP Florida Department of Environmental Protection

DGPS Differential Global Positioning System

ERP Environmental Resource Permitting

FAC facultative

FACW facultative wet

FWS U.S. Fish and Wildlife Service

GS Green Swamp Wildlife Management Area

HRSP Hillsborough River State Park

NTB Northern Tampa Bay

NWI National Wetlands Inventory

OBL obligate

SWFWMD Southwest Florida Water Management District

SWP Jay B. Starkey Wilderness Park

TBW Tampa Bay Water

TOPCON Topcon Total Station

USGS U.S. Geological Survey

WAP Wetland Assessment Procedure

WUP Water Use Permit

vi 

Acronyms and Additional Abbreviations
Bathymetry and Vegetation in Isolated Marsh 

and Cypress Wetlands in the Northern Tampa Bay 

Area 2000-2004

By Kim H. Haag, Terrie M. Lee, and Donald C. Herndon

Abstract 

Wetland bathymetry and vegetation mapping are two 

commonly used lines of evidence for assessing the hydrologic 

and ecologic status of expansive coastal and riverine wetlands. 

For small isolated freshwater wetlands, however, bathymetric 

data coupled with vegetation assessments are generally scarce, 

despite the prevalence of isolated wetlands in many regions of 

the United States and the recognized importance of topography 

as a control on inundation patterns and vegetation distribution.

In the northern Tampa Bay area of west-central Florida, 

bathymetry was mapped and vegetation was assessed in five 

marsh and five cypress wetlands. These 10 isolated wetlands 

were grouped into three categories based on the effects of 

ground-water withdrawals from regional municipal well fields: 

natural (no effect), impaired (drier than natural), and augmented 

(wetlands with artificially augmented water levels). Delineation 

of the wetland perimeter was a critical component for estimating 

wetland-surface area and stored water volume. The wetland 

perimeter was delineated by the presence of Serenoa repens (the 

“palmetto fringe”) at 9 of the 10 sites. At the 10th site, where the 

palmetto fringe was absent, hydric-soils indicators were used to 

delineate the perimeter. Bathymetric data were collected using 

one or more techniques, depending on the physical characteristics of each wetland. Wetland stage was measured hourly using 

continuous stage recorders. Wetland vegetation was assessed 

semiannually for 2 1/2 years in fixed plots located at three distinct elevations. Vegetation assessments were used to determine 

the community composition and the relative abundance of obligate, facultative wet, and facultative species at each elevation.

Bathymetry maps were generated, and stage-area and 

stage-volume relations were developed for all 10 wetlands. 

Bathymetric data sets containing a high density of data points 

collected at frequent and regular spatial intervals provided the 

most useful stage-area and stage-volume relations. Bathymetric 

maps of several wetlands also were generated using a low density 

of data points collected along transect lines or contour lines. In 

a comparative analysis of the three mapping approaches, stagearea and stage-volume relations based on transect data alone 

underestimated (by 50-100 percent over certain ranges of stage) 

the wetland area and volume compared to results using a high 

density of data points. Adding data points collected along one 

elevation contour below the wetland perimeter to the transect 

data set greatly improved the agreement of the resulting stagearea and stage-volume relations to the high-density mapping 

approach. 

Stage-area relations and routinely monitored stage data 

were used to compare and contrast the average flooded area in 

a natural marsh and an impaired marsh over a 2-year period. 

Vegetation assessments used together with flooded-area information provided the potential for extrapolating vegetation 

results from points or transects to wetlands as a whole. A comparison of the frequency of flooding of different areas of the 

wetland and the species composition in vegetation plots at different elevations indicated the dependence of vegetation on 

inundation frequency. Because of the broad tolerances of many 

wetlands plants to a range of inundation conditions, however, 

vegetation assessments alone provided less definitive evidence 

of the hydrologic differences between the two sites, and hydrologic changes occurring during the 2 years, than the floodedarea frequencies.

Combining flooded-area frequencies with vegetation 

assessments could provide a more versatile and insightful 

approach for determining the ecological status of wetlands than 

using vegetation and stage data alone. Flooded-area frequencies 

may further provide a useful approach for assessing the ecological status of wetlands where historical vegetation surveys and 

stage data are lacking. Comparing the contemporary floodedarea frequencies and vegetation in impaired or augmented wetlands to the flooded-area frequencies of natural wetlands with 
2 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

similar geologic and climatic settings provides a method to 

assess the impacts of human activities on hydrology and ecology. The approach requires first determining flooded-area frequencies in a representative population of natural (or reference) 

wetlands. Because the variables are spatial, such comparisons 

can be used to interpret the extent of wetland mitigation 

achieved using augmentation, and to objectively assess the area 

of wetlands affected by human activities.

Bathymetric data, historical stage data, stage-area and 

stage-volume relations, and vegetation community assessment 

are all important tools for water managers tasked with assessing 

wetland status and the impacts of human activities on wetlands. 

Together these data sets can be used as tools to refine understanding and management of wetland systems.

Introduction

Hydrologic processes in wetlands give rise to the characteristic hydric soils and hydrophytic vegetation that define 

these complex ecosystems (Gosselink and Turner, 1978; 

Carter, 1986; Duever, 1988; National Research Council, 1995). 

The importance of wetland hydrology contrasts sharply with 

the relative lack of published data on the subject, and there are 

relatively few comprehensive studies that describe in detail the 

hydrologic characteristics of specific wetland types (Mitsch 

and Gosselink, 1993). Variations in inundation frequency, 

depth duration, and seasonality of water levels result in the distinctive habitat zonation found in wetlands. These hydrologic 

characteristics are influenced by topography and other physical 

features of the terrain. Yet despite the recognized importance of 

topography as a control on wetland hydrology and ecosystem 

structure, topographic data generally are not available for small 

wetlands (less than 10 acres) in isolated depressions (Winter, 

1988; Wise and others, 2000; Brooks and Hayashi, 2002). In 

contrast, topographic data are more readily available for coastal 

marsh wetlands (Ramsey and others, 1998) where elevation 

contours that determine the frequency, duration, and depth of 

flooding have been assessed at large scales using remote sensing.

To describe the seasonal flooding cycle in small isolated 

wetlands, water depth is monitored over time at the deepest 

point in a wetland, and the water-level fluctuations at this point 

are assumed to be characteristic of the wetland feature as a 

whole. The validity of this assumption commonly goes 

untested because topographic (bathymetric) data rarely are 

available to describe the percentage of wetland area flooded at 

water levels below maximum depth (Ward, 1998). Water depth 

measured at a staff gage, although monitored regularly and 

often in conjunction with periodic vegetation assessments, provides little in the way of useful feedback to vegetation surveys 

unless the entire wetland is flooded. Even when water depth is 

measured at the site of a vegetation assessment, rarely is it 

related back to the water depth at the staff gage or at the deepest 

point. Bathymetric data also are a prerequisite to describing 

other facets of wetland hydrology. For example, the relations 

between water level (stage), wetland area, and volume are 

dependent on bathymetry, and bathymetric data are needed to 

describe wetland water budgets as well as to describe the error 

accompanying water-budget calculations.

Hydrologic characteristics have a fundamental influence 

on the spatial distribution of freshwater vegetation (Harris and 

Marshall, 1963; Spence, 1982; Schalles and Shure, 1989; 

Squires and van der Valk, 1992; Ross and others, 2003). Shifts 

in the wetland vegetation community composition are a primary 

line of evidence for assessing the ecological condition of wetlands in many types of wetland assessments (Bartoldus, 1999a,b, 

2000). In turn, changes in the vegetation community commonly 

are used to indicate changes in the hydrologic conditions of wetlands. Inferring hydrologic trends based on changes in wetland 

plant communities has limitations, however, because a wetland 

plant community at a given point in time is reflective of conditions in the “recent” past but not necessarily those of the immediate present (Lewis, 2001) or the more distant past. Typically, 

there is a time lag between hydrologic alterations and changes 

in vegetation community composition (van der Valk and Welling, 1988). Furthermore, many wetland species are tolerant of 

well-drained soils, for if they were not they could not withstand 

the dry intervals that affect wetlands. Thus, the ability to discern 

patterns in vegetation related to alterations in wetland water 

level is complicated by the substantial variation and overlap of 

hydrologic tolerances of wetland vegetation (Squires and 

van der Valk, 1992). 

Vegetation surveys used in conjunction with topographic 

data and stage data can improve substantially the ability to 

assess changes in the ecological status of wetlands. With topographic data, changes in water-level regime recorded at a staff 

gage can be extrapolated spatially, and vegetation assessments 

based on point or transect data can be considered in association 

with spatial patterns of inundation. A large number of isolated 

marsh and cypress wetlands are present in comparable geologic 

settings with similar water sources in the northern Tampa Bay 

(NTB) area. Many of these wetlands have historical water-level 

data and vegetation surveys. The addition of bathymetric data to 

these data sets provides a unique approach to investigate the 

complex relations between wetland bathymetry, depth-areavolume relations, and vegetation.

Purpose and Scope

The purpose of this report is to describe the bathymetry 

and vegetation of 10 isolated wetlands in the NTB area. Specifically, the report: (1) describes relations between wetland water 

level (stage), the area of inundation, and stored water volume; 

(2) compares several bathymetric data collection and analysis 

techniques; (3) describes wetland vegetation in relation to 

bathymetric contours and water depth; and (4) discusses the 

potential relation between vegetation and the frequency of 

inundation at different bathymetric contours.
Introduction 3

Bathymetric data were collected using one or more 

techniques, depending on the physical characteristics of the 

wetlands. Stage-area-volume relations were developed from 

U.S. Geological Survey (USGS) data collected during 2000-

2004. Wetland vegetation was assessed in fixed plots semiannually over a 2 1/2-year period. This report is part of a larger 

study of the effects of augmentation on hydrology, water quality, and ecology in isolated marsh and cypress wetlands in the 

NTB area. The study was conducted by the USGS in cooperation with Pinellas County, the Southwest Florida Water 

Management District (SWFWMD), and Tampa Bay Water.

Background

Freshwater wetlands are a widespread and distinctive 

feature of the Florida landscape (Darst and others, 1995). 

Wetlands give rise to a unique vegetative community, and their 

value as fish and wildlife habitat is considerable (Hart and 

Newman, 1995). In west-central Florida, freshwater wetlands 

consist of both forested and non-forested types, including riverine swamps, lacustrine swamps, cypress domes, marshes, and 

wet prairies (Southwest Florida Water Management District, 

1999). A 1986 inventory of 71 square miles (mi2) in the NTB 

area indicated that wetlands account for about 23 percent of the 

total acreage surveyed. 

A substantial percentage (92 percent) of the total number 

of wetlands in the NTB area are isolated wetlands, and isolated 

wetlands compose 68 percent of the total wetland acreage. Moreover, small isolated wetlands less than 5 acres in size account 

for 79 percent of the total number of isolated wetlands and 34 

percent of the total isolated wetland acreage (Manuel Lopez, 

SWFWMD, written commun., 2002). The term “isolated wetland” 

is not a precise scientific or regulatory term, but in general is 

used to define a wetland that lacks a surface outlet to a downstream river (Leibowitz, 2003). Many isolated wetlands, however, have natural areas of outflow during flood conditions 

when stage exceeds the elevation of the wetland perimeter. 

Likewise, isolated wetlands also can receive inflow generated 

by outflow from an upgradient wetland (Winter and LaBaugh, 

2003). Wetlands develop these intermittent connections at 

recurrence intervals that can be predicted based on a knowledge 

of precipitation patterns and other climatic variables (Winter 

and LaBaugh, 2003).

A majority of isolated marshes and stillwater cypress 

swamps in west-central Florida are supplied with water from 

precipitation and shallow, acidic ground water (Myers and 

Ewel, 1990). In these isolated wetlands, where the water table 

approaches land surface seasonally under natural conditions, 

the hydroperiod is largely determined by differences between 

precipitation and evapotranspiration, and is mediated by geology and topography. Small changes in wetland stage can cause 

large changes in wetland-surface area, because there is little 

local topographic relief. Persistent changes in wetland water 

levels, as a result of changes in rainfall or human activities, can 

in turn cause a substantial change in the vegetation of hundreds 

or thousands of acres of land in the NTB area.

 Rapid increases in Florida’s west coast population during 

1970-2000 have had two important effects on isolated wetlands. 

First, land development has caused elimination or fragmentation of wetlands, reducing their effective size and associated 

habitat value for wildlife. Second, the demand for potable water 

supply has increased the ground-water withdrawal rate, measurably lowering the potentiometric surface in the Upper Floridan 

aquifer. A lower potentiometric-surface elevation in the Upper 

Floridan aquifer reduces the potentiometric surface of the surficial aquifer, and lowers the stage (surface-water elevation) of 

wetlands in nearby areas (Berryman and Henigar, Inc., 1995). 

On municipal well fields, wetlands close to production wells 

may exhibit substantially reduced surface-water levels with 

much shorter and less frequent inundation than wetlands not 

influenced by human activities (Biological Research Associates, Inc., 1996). Effects of decreased depth and frequency of 

inundation on wetland vegetation range from minimal to severe. 

Changes in wetland vegetation community composition can 

occur, and there may be associated changes in habitat value for 

wildlife (Dooris and others, 1990; CH2M HILL, 1996). Oxidation 

and compaction of exposed wetlands soils causes loss of root 

support and subsequent treefall in cypress wetlands (Rochow, 

1985, 1994). Treefall in these systems opens the canopy and 

facilitates encroachment of upland species.

Protecting the quality of Florida’s wetlands is the responsibility of the Florida Department of Environmental Protection 

(FDEP). The FDEP Environmental Resource Permitting (ERP) 

Program is designed to ensure that activities in uplands, wetlands, and other surface waters do not degrade water quality or 

degrade habitat for aquatic or wetland-dependent wildlife. The 

SWFWMD shares the responsibility of implementing the ERP 

Program in west-central Florida. Water-use activities by 

regional water utilities such as Tampa Bay Water are regulated 

by the SWFWMD under the Consolidated Water Use Permit 

(WUP) Program. As part of Tampa Bay Water’s WUP for its 11 

regional well fields, Tampa Bay Water developed an Environmental Management Plan (EMP). The EMP addresses management of the well fields, and proposes mitigation alternatives to 

regain wetland values that have been lost due to ground-water 

withdrawals. Augmentation (rehydration) with ground water is 

one mitigation alternative that has been used long-term (for 

more than 15 years) in about 15 wetlands on well fields in the 

NTB area (John Emery, SWFWMD, oral commun., 2005).

Site Selection

The isolated wetlands (five marsh and five cypress) 

selected for study range in size from about 1-9 acres (table 1), 

and maximum depths range from about 1-8 feet (ft). Isolated 

wetlands of this size are common throughout the NTB area. 

Wetland sites with existing data collection programs were given 

preference in the selection process.
Table 1. Names, locations, and physical characteristics of study wetlands.

[USGS, U.S. Geological Survey; N, north; W, west; sec, section; T, township; S, south; R, range; SWFWMD, Southwest Florida Water Management District; latitude and longitude iminutes (′), and seconds (′′)]

Wetland name

USGS

wetland

name

Alternate names

Period

of hydrologic

record

County Latitude Longitude Location1 Size (acres) Maximum depth (feet) 

Cross Bar RanchWell FieldDuck Pond Marsh

DuckPondMarsh

Q-04 1978-present Pasco 28o21′59′′Ν 82o28′02′′W sec. 25, T. 24 S., 

R. 18 E,Ehren, FL

5.2 8.13 

Green SwampWildlife ManagementArea Cypress

GSCypress

Green Swamp 5;SWFWMDStation 541

1979-present Sumter 28o24′47′′Ν 81o57′40′′W sec. 12, T. 24 S., 

R. 23 E.,Bay Lake, FL

1.7 1.69 

Green SwampWildlife Management Area Marsh

GSMarsh

SWFWMDStation 605

1995-present Sumter 28o21′16′′Ν 82o01′02′′W sec. 33, T. 24 S., 

R. 23 E.,Branchborough, FL

1.6 1.07 

HillsboroughRiver State Park Marsh

HRSPMarsh

SWFWMD Station 378

1977-present Hillsborough 28o08′49′′Ν 82o13′41′′W sec. 8, T. 27 S., R. 21 E.,

Zephyrhills, FL

2.2 2.65 

Jay B. Starkey Wilderness ParkS-63 Cypress

S-63Cypress

-- 1983-present Pasco 28o14′55′′Ν 82o35′00′′W sec. 2, T. 26 S., 

R. 17 E.,Odessa, FL

1.3 1.47 

Jay B. Starkey Wilderness ParkS-68 Cypress

S-68Cypress

STWF-DD;SWFWMDStation 209

1983-present Pasco 28o14′21′′Ν 82o34′31′′W sec. 11, T. 26 S., 

R. 17 E.,Odessa, FL

5.8 1.55 

Cypress Creek Well Field W-03 Marsh

W-03Marsh

C-2 Marsh;SWFWMDStation 482

1978-present Pasco 28o18′13′′Ν 82o22′40′′W sec. 14, T. 25 S., 

R. 19 E.,Ehren, FL

7.4 5.44 

Cypress Creek Well Field W-05 Cypress

W-05Cypress

T-1 Cypress Head;CCWF A

1978-present Pasco 28o18′18′′Ν 82o22′55′′W sec. 14, T. 25 S., 

R. 19 E,Ehren, FL

8.8 2.11 

Cypress Creek Well Field W-19 Cypress

W-19Cypress

C-10 Cypress Head 1978-present Pasco 28o16′42′′Ν 82o23′52′′W sec. 27, T. 25 S., 

R. 19 E,Ehren, FL

2.1 2.70 

Cypress Creek Well Field W-29 Marsh

W-29Marsh

Cottonmouth Marsh;Rattlesnake Marsh

1978-present Pasco 28o17′54′′Ν 82o23′13′′W sec. 22, T. 25 S., 

R. 19 E.,Ehren, FL

6.5 2.76 

1USGS 1:24,000 topographic map name.
Introduction 5

Three principal environmental conditions, or wetland 

types, are defined in the context of this investigation to describe 

the 10 study wetlands in the NTB area:

• Natural wetlands are defined as being unaffected or 

minimally affected by human activities including 

ground-water withdrawal. Four wetlands (two marsh 

and two cypress) were chosen to characterize the 

hydrologic conditions and vegetation of natural wetlands within the NTB area. 

• Impaired wetlands are defined as wetlands that have 

been affected by ground-water withdrawals for several 

years and typically are dry for a longer period of the 

year than natural wetlands. Two wetlands (one marsh 

and one cypress) were selected to characterize the 

hydrologic conditions and vegetation of impaired 

wetlands within the NTB area.

• Augmented wetlands are defined as wetlands that have 

been affected by ground-water withdrawal and that 

have been augmented with ground water for at least 15 

years. Four augmented wetlands (two marsh and two 

cypress) were selected to characterize the hydrologic 

conditions and vegetation of augmented wetlands 

within the NTB area.

Description of the Study Area

The NTB area encompasses about 1,800 mi2 of west-central 

Florida, including parts of Hernando, Hillsborough, Lake, 

Pasco, Polk, Pinellas, and Sumter counties (fig. 1). All 10 study 

sites are within the NTB area, and all are located either in well 

fields or on publicly owned lands (wildlife management areas 

or parks) in two physiographic regions (fig. 1). These regions 

(Gulf Coast Lowlands and Western Valley) (White, 1970) are 

characterized by a relatively high water table and are underlain 

by the Upper Floridan aquifer, which is semi-confined or 

unconfined in the study area. Land use and human activities in 

the vicinity of the study sites are described briefly. 

The Cross Bar Ranch Well Field (CBR) encompasses 

about 12.5 mi2 of land in north-central Pasco County (fig. 1). 

The CBR has been in production since 1980, and averages 

about 20 million gallons per day (Mgal/d) since 1996 (Biological 

Research Associates, Inc., 2001). The CBR is a multi-use facility; some of the CBR is conservation area, managed for wildlife, and about 45 percent of the acreage is cultivated as a pine 

plantation. There are several lakes and ponds on the property 

as well as wet prairies, marshes, and cypress ponds. Some 

wetlands have been augmented since the 1980s (Biological 

Research Associates, Inc., 2001), including Duck Pond Marsh 

(augmented since 1987) (fig. 1). 

The Cypress Creek Well Field (CCW) encompasses about 

7.7 mi2 of land in central Pasco County (fig. 1). The land within 

the well field is in a relatively natural condition and is used as 

a wilderness park. The property has numerous isolated marsh 

and cypress wetlands, and the stream bed of historical Cypress 

Creek has been dry for long periods during recent years 

(Reynolds, Smith & Hills, Inc., 2001). In areas surrounding 

the well field, land-use activities include ongoing residential 

development and agriculture. The CCW has been in production 

since 1976 and produces about 30 Mgal/d from the Upper Floridan aquifer (Reynolds, Smith & Hills, Inc., 2001). Many of the 

wetlands on the CCW have been affected by declining groundwater levels, and some of them have been augmented for more 

than 20 years (Berryman and Henigar, 1995; Rochow, 1998; 

Reynolds, Smith & Hills, Inc., 2001). Four study sites are 

located in the CCW: W-03 Marsh (augmented since 1979), 

W-05 Cypress (augmented since 1978), W-19 Cypress 

(impaired), and W-29 Marsh (impaired) (fig. 1).

The Green Swamp Wildlife Management Area (GS), 

previously know as the Green Swamp Flood Detention Area, 

encompasses about 75 mi2 in Hernando, Lake, Pasco, Polk, and 

Sumter Counties (fig. 1). There is little development of the 

ground-water resource in this area, and surface-water levels are 

largely unaffected by human activities. Wetlands cover about 

one-third of the GS, and much of the remainder is covered in 

natural pine flatwoods. Natural cypress wetlands are extensive, 

whereas marsh wetlands cover less than 1 percent of the GS 

(Southwest Florida Water Management District, 1985). Several 

long-term wetland monitoring sites have been established and 

monitored by the SWFWMD, and these sites can be used to 

characterize conditions in natural wetlands (Rochow and 

Lopez, 1984). Two natural study wetlands are located in the GS: 

Green Swamp Marsh and Green Swamp Cypress (fig. 1). 

The Hillsborough River State Park (HRSP) in northeastern 

Hillsborough County (fig. 1) encompasses about 6 mi2 of pine 

flatwoods and live oak hammocks interspersed with natural 

marsh wetlands; surface-water levels are largely unaffected by 

human activity. The Hillsborough River is bordered by riverine 

wetlands, and flows through the western part of the Park. One 

natural wetland (Hillsborough River State Park Marsh) was 

selected as a study site in HRSP (fig. 1).

The Jay B. Starkey Wilderness Park (SWP) is located in 

southwestern Pasco County and encompasses about 13 mi2

(fig. 1). The Park includes an operational well field (Starkey 

Well Field), as well as pine flatwoods, sandhills, hardwood 

hammock, freshwater marshes, cypress ponds, and two bands of 

riverine swamp associated with the Anclote and Pithlachascotee 

Rivers. The well field began production in 1974. Some wetland 

ecosystems have been affected by well-field development, 

whereas others have not (Rochow, 1998; Berryman and Henigar, 2001). Two study sites, S-63 Cypress (augmented since 

1990) and S-68 Cypress (natural), are located in different parts 

of SWP (fig. 1).

Acknowledgments

Lauren Pusateri of the USGS, Tampa, provided valuable 

assistance with many aspects of data collection. The authors are 

grateful to Ted Rochow and David Carr of the SWFWMD for 

their contributions to identifying vegetation and increasing our 

understanding of normal pool indicators. Melanie Darst, Patty 

Fesmire, Michael Hancock, Warren Hogg, Helen Light, Ted 

Rochow, Donald Rosenberry, and Dave Slonena provided helpful 

reviews of the report.
6 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004 River

Pithlachascotee

River

Anclote

River

Hillsborough

River

Hillsborough

Creek

Cypress

Blackwater

Creek

Withlacoochee

Alafia

River

River

EXPLANATION

8 7

9 10

2

3

4

1

5 6

1

2

3

4

5

S-68 Cypress

W-03 Marsh

W-05 Cypress

W-19 Cypress

W-29 Marsh

Duck Pond Marsh

Green Swamp Cypress

Green Swamp Marsh

Hillsborough River State Park Marsh

S-63 Cypress

6

7

8

9

10

6 SELECTED WETLAND AND NUMBER

28 30' °

15'

28 0 °0 '

82°45' 30' 15' 82°00'

0 5 10 MILES

0 5 10 KILOMETERS

Base from U.S. Geological Survey digital

data, 1:24,000, datum nad83

Albers Equal-Area Conic Projection,

Standard parallels 29 30 and 45 30 ,

central meridian -83 00

° °

°

' '

'

FLORIDA

LOCATION

OF STUDY

AREA

Hillsborough

River State Park

Cypress

Creek

Well field

Cross Bar

Ranch

Well field

Jay B. Starkey

Wilderness

Park

HERNANDO COUNTY

PASCO COUNTY

HILLSBOROUGH

COUNTY

POLK COUNTY

PINELLAS

COUNTY

SUMTER

COUNTY

Brooksville

Land O Lakes

New

Port

Richey

Temple

Terrace

Tarpon

Springs

Clearwater

Tampa

Brandon

Plant City

Zephyrhills

Lakeland

Dade

City

OLD

TAMPA

BAY

GULF OF MEXICO

LAKE

COUNTY

Northern Tampa Bay Area

GREEN SWAMP

PARKS AND WELL FIELDS

PHYSIOGRAPHIC REGIONS

Gulf Coast Lowlands

Western Valley

Figure 1. Location of study wetlands in the northern Tampa Bay area, west-central Florida.
Methods of Data Collection and Analysis 7

Methods of Data Collection and Analysis

The delineation of the wetland perimeter at each study site 

was a prerequisite for all subsequent data collection. Once the 

wetland perimeter was delineated, the perimeter elevation was 

determined. Wetland stage was measured at staff gages, and 

bathymetric data were collected throughout the interior of each 

wetland using one or more approaches. Bathymetric contour 

maps were drawn, and wetland area and stored water volume 

were calculated. The potential effect of different mapping 

approaches on calculated wetland area and water volume estimates was investigated at two wetland sites. Vegetation was 

identified to species, and relative abundance was determined 

semiannually in replicate fixed plots at known elevations at all 

study sites.

Delineation of the Wetland Perimeter and 

Determination of Perimeter Elevations

The wetland perimeter encompasses the maximum areal 

extent of a wetland. By definition, when water reaches the wetland perimeter, it is 100 percent inundated. The presence of 

Serenoa repens (saw palmetto) is commonly used to delineate 

wetland perimeters in Florida because this long-lived terrestrial 

shrub cannot survive inundation of its prostrate trunks for more 

than a few weeks. Therefore, the presence of saw palmetto at a 

particular elevation indicates that water is rarely at land surface 

above that point. Nine of the 10 study wetlands (excluding Duck 

Pond Marsh) are partially or completely surrounded by saw palmetto. As a result, the palmetto fringe at these sites was defined 

as the wetland perimeter. Perimeter coordinates were collected at 

approximately 30-ft intervals using a hand-held Garmin eTrex 

Legend Differential Global Position System (DGPS) unit. After 

plotting the DGPS data points using Arcview Geographic Information System software, the location of the entire perimeter was 

then interpolated. 

The perimeter elevation for 9 of the 10 study wetlands was 

determined by the SWFWMD as a part of an ongoing study of 

vegetative “normal-pool” indicators in the NTB area. The concept of a normal pool was developed by the SWFWMD to establish a standard elevation datum that would facilitate comparisons 

of hydrology between wetlands (Mike Hancock, SWFWMD, 

written commun., 2004). SWFWMD determined in their study 

that the normal pool elevation of a cypress wetland can be identified consistently by the elevations of three vegetative normal 

pool indicators: the inflection point on the buttress of cypress 

trees (Taxodium spp.); the lower limit of epiphytic bryophytes 

(the moss collar) growing on cypress trees; and the elevation of 

the root crowns of mature specimens of Lyonia lucida on 

cypress trees (Carr and Rochow, 2004). As a part of their study, 

SWFWMD made concurrent measurements of the elevations of 

the cypress normal pool indicators and the rooted base of 

Serenoa repens (the “saw palmetto fringe”) at those sites where 

the indicators and the palmetto fringe were both present. The 

SWFWMD determined that the cypress indicators at hydrologically unaltered wetlands are consistently 0.24 ft above the 

median elevation of the rooted base of Serenoa repens (Carr and 

Rochow, 2004). This consistent difference means that in the 

NTB area, the elevation of a cypress normal pool indicator can 

be measured to determine the elevation of the palmetto fringe. 

The SWFWMD made five elevation measurements of the 

normal pool indicator at each of these nine sites, and the median 

value was reported (table 2). The SWFWMD surveyed the elevation of the normal pool indicators from existing benchmarks 

(tables 2, 3). At some sites (Duck Pond Marsh, Hillsborough 

River State Park Marsh, W-19 Cypress, and W-29 Cypress), 

these elevations did not agree with independent surveys by 

USGS from other benchmarks. Corrections (offsets) were 

applied to SWFWMD benchmark elevations at these sites 

because of the discrepancy between benchmarks to establish 

consistency with bathymetric and other data collected for this 

study. For this report, all elevations are relative to the National 

Geodetic Vertical Datum of 1929 (NGVD of 1929).

The location and the elevation of the wetland perimeter at 

Duck Pond Marsh was determined by the presence of hydric soils 

(Hurt and others, 2000), because land-management practices have 

eliminated saw palmetto from the area. Hydric soils form under 

conditions of saturation such that anaerobic conditions develop 

and persist over time (Richardson and Vepraskas, 2001). Soil core 

samples collected by the SWFWMD along a single transect at 

several distances onshore at Duck Pond Marsh were analyzed to 

determine the vertical location of hydric soils (David Carr, 

SWFWMD, oral commun., 2003). Markers were placed along the 

transect at locations where hydric soils were present 3, 6, and 12 

inches below land surface. Using Topcon Total Station Model 

GTS-303D surveying equipment (Topcon), the land-surface elevation at each soil depth was determined, and from the three landsurface elevations, three elevations of hydric-soils indicators were 

determined. The mean of these three elevations was selected to 

represent the elevation at which 100 percent of the wetland would 

be inundated. This elevation then was used to determine the 

perimeter of the wetland at Duck Pond Marsh. Pairs of elevation 

points were measured around the edge of the wetland using the 

Topcon, with each pair consisting of one upslope measurement 

and one downslope measurement from the 100-percent inundation elevation. The actual perimeter points were then estimated by 

interpolation between the pairs of values.

Measurement of Wetland Stage and Collection of 

Bathymetric Data

Wetland stage has been monitored for at least a decade at 

each of the 10 wetland sites, and up to 25 years at some sites. 

At each site, wetland stage could be measured by reading the 

water level on a staff gage located within the wetland. Three of 

the 10 wetlands had more than one staff gage. For example, three 

staff gages were present in Duck Pond Marsh at different distances from the wetland perimeter. It should be noted that from 

time to time, staff gages are added or removed by agencies
8 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

Table 2. Indicators of normal pool elevation and elevation of palmetto fringe at wetland edge.

[SWFWMD, Southwest Florida Water Management District; USGS, U.S. Geological Survey; na, not applicable; all elevations in 

feet above NGVD of 1929]

Wetland name Normal pool

indicators

SWFWMD

elevation of

normal pool

indicators1

Palmetto fringe

elevation derived

from normal

pool indicators

Offset from

SWFWMD

elevation to

USGS elevation

USGS elevation

of wetland 

perimeter

at wetland edge

Duck Pond Marsh Hydric Soils na na na 70.48

Green Swamp Cypress Lyonia 98.80 98.56 20 98.56

Green Swamp Marsh Palmetto Fringe 93.30 93.30 0 93.30

Hillsborough River

State Park Marsh

Palmetto Fringe 46.08 46.08 0.27 46.35

S-63 Cypress Lyonia 42.56 42.32 0 42.32

S-68 Cypress Lyonia 43.90 43.66 0 43.66

W-03 Marsh Palmetto Fringe 72.44 72.44 0 72.44

W-05 Cypress Buttress Swelling 71.71 71.47 0 71.47

W-19 Cypress Buttress Swelling 63.47 63.23 na 63.23

W-29 Marsh Palmetto Fringe 69.86 69.86 0.06 69.92

1Reported elevation is the median of five elevation measurements.

2SWFWMD field notes unavailable; offset assumed to be 0.

Table 3. Benchmark names, USGS elevations, and offsets.

[USGS, U.S. Geological Survey; SWFWMD, Southwest Florida Water Management 

District; TBM, temporary benchmark; RM, reference mark]

Wetland name Benchmark name

Elevation1

of 

benchmark

Offset2

Duck Pond Marsh USGS Well A-2 deep

SWFWMD TBM 25-24-18-2

78.16

75.64

0

0.05

Green Swamp Cypress SWFWMD TBM 12-24-23-1 99.77 0

Green Swamp Marsh SWFWMD TBM 33-24-23-1 96.00 0

Hillsborough River State 

Park Marsh

USGS RM 9

SWFWMD TBM 8-27-21-3

43.05

48.83

0

0.27

S-63 Cypress SWFWMD TBM 02-26-17-6 43.39 0

S-68 Cypress SWFWMD TBM 11-26-17-18 44.83 0

W-03 Marsh SWFWMD TBM 14-25-19-5 76.99 0

W-05 Cypress SWFWMD TBM 14-25-19-2 72.53 0

W-19 Cypress SWFWMD TBM 27-25-19-2

SWFWMD TBM 27-25-19-7

67.96

64.84

0

-0.04

W-29 Marsh SWFWMD TBM 23-25-19-5

SWFWMD TBM 22-25-19-9

73.77

70.67

0

0.06

1All elevations in feet above NGVD of 1929.

2Offsets to be applied to SWFWMD benchmark elevations for compatibility 

with USGS elevations presented in this report.

An open canopy and 

shallow water foster 

the dense growth of 

understory plants at 

S-63, an augmented 

cypress wetland.

Shade and deep 

water inhibit the 

growth of aquatic 

plants in the center 

of S-68, a natural 

cypress wetland.
Methods of Data Collection and Analysis 9

monitoring wetlands. To avoid confusion in this study, each 

staff gage was uniquely identified using the reading at the top 

of the staff gage plate, and the locations of all staff gages at the 

10 wetlands were determined using DGPS (see app. 1). Elevation 

surveys were run to all staff gages from well-defined benchmarks (table 3). If needed, staff gages were assigned correction 

factors (offsets) based on the USGS surveying results to produce stage expressed as elevation in feet above NGVD of 1929. 

Wetland stage was measured hourly with continuous stage 

recorders in each of the study wetlands using established 

methods (Buchanan and Somers, 1982).

Detailed bathymetric maps provide the basis for defining 

the relation between stage, area of inundation, and stored volume of water in a wetland. Bathymetry of the 10 study wetlands 

was described using two principal approaches, or a combination 

of the two, as described in detail in the following paragraphs. 

More than one approach was needed to collect bathymetric data 

because the wetlands differ in their depth, size, extent of inundation, and density of vegetation. Methods for surveying the 

land-surface elevation or topography of the wetlands were 

chosen based on available line of sight (an unobstructed path 

across which measurements can be made) and the depth of 

water present in each wetland.

At the five sites where there was an available line of sight 

(W-29 Marsh, HRSP Marsh, GS Marsh, W-19 Cypress, S-63 

Cypress), Topcon was used to survey land-surface elevations. 

The Topcon tripod was set up in the interior of the wetland and 

a point of known location, determined by DGPS, was surveyed 

to determine the location of the tripod. Then elevation data 

points were collected approximately 20-30 ft apart as the rod 

was moved throughout the wetland. The rod was moved either 

along a grid pattern, or in a radial pattern moving away from the 

Topcon tripod. The tripod was set up multiple times in different 

locations if the wetland was large, or if the line of sight was 

limited.

At the three sites where water was present over approximately 100 percent of the wetland area at the time of data collection (GS Cypress, S-68 Cypress, and Duck Pond Marsh), 

DGPS and the measured depth of water below a known elevation were used to determine the elevation of the land surface 

along lines transecting the wetlands. The horizontal locations 

of points along the transect lines usually were determined using 

DGPS. In parts of these wetlands where the canopy was dense 

and the DGPS signal could not be detected, a compass was used 

to obtain direction and a measuring tape was used to determine 

the horizontal distance from a known location. At GS Cypress 

and S-68 Cypress, which are both natural wetlands, flocculent 

bottom sediment was scant and the depth of water was measured directly to the sandy bottom using a graduated rod. Water 

depth subtracted from the wetland stage provided the elevation 

of points on the transect lines. At Duck Pond Marsh, which contained deep flocculent sediments characteristic of augmented 

sites, the water was too deep to visualize the top of the sediment 

layer. As a result, the water depth was measured using a graduated rope attached to a Secchi disk, which was lowered to the 

top of the flocculent sediment layer.

At the two remaining sites (W-03 Marsh and W-05 

Cypress), the water surface did not cover the entire wetland and 

the line of sight was limited in some areas, so a combination of 

approaches was used. The Topcon was used to survey the elevation of dry areas and areas with a clear line of sight. In wet 

areas without a clear line of sight, the depth below the water surface was measured with a graduated rod. At W-03 Marsh, the 

northwestern part of the wetland had poor access because of 

very dense shrub vegetation and data points are sparse. At W-05 

Cypress, there was a deep layer of flocculent bottom material. 

At this site, two depths of water were determined at each point 

(depth to hard bottom and depth to the top of the flocculent 

layer), and these depths were averaged.

The Topcon instrument had a precision of + 0.01 ft for elevation and +0.1 ft for horizontal distance, over ranges used in 

this study. The bathymetric mapping approach using a Topcon 

instrument was preferred because of the precision of the instrument. Topcon typically was used when the wetland was small 

and the line of sight was not limited. This approach could not be 

used at five of the study sites, however, because of deep water 

or a high density of trees and a short line of sight. The DGPS 

instrument was used for mapping the horizontal location of 

bathymetric data points at these sites, but it was less precise 

than the Topcon instrument. In marshes with no tree cover, the 

location of data points mapped by DGPS had a precision of 

+10-15 ft. In cypress wetlands with a dense tree canopy, interference resulted in a weaker DGPS signal and the precision of 

the instrument was <45 ft. The depth of water determined using 

a graduated rope or rod at five of the sites had a precision of 

+0.01 ft, and the depth of water measured at Duck Pond using a 

Secchi disk had a precision of 0.1 ft. 

Efforts were made to collect a large number of bathymetric 

data points at all sites. Topcon was used to collect about 62 

points per acre at GS Marsh, 59 points per acre at S-63 Cypress, 

49 points per acre at HRSP Marsh, and 35 points per acre at 

W-19 Cypress. Bathymetric data also were collected with the 

Topcon at W-29 Marsh, but because of its large size only 18 

points per acre were collected. In two of the other large wetlands (Duck Pond Marsh and S-68 Cypress), DGPS and the 

depth of water were used to map bathymetry. The density of 

data points was lower at these sites (about 11 points per acre and 

8 points per acre, respectively) not only because of their large 

size but also because of deep water at the former site, and a high 

density of trees at the latter site. 

Fallen trees, leaning trees, small hummocks of vegetation, 

and small holes generally were avoided during surveying in an 

attempt to describe the elevation of the wetland bottom on a 

large scale. Wetland soils commonly are highly organic at the 

surface and compressible, compacting during dry periods and 

expanding when rewetted. These and other characteristics of 

wetland surfaces affect estimates of stage-area and stage-volume derived by bathymetric mapping, and have their greatest 

effect on estimates generated from bathymetric data with a low 

density of data points. In this study, however, we assumed that 

the contribution of these sources of error were equivalent for 

each mapping approach.
10 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

Creation of Bathymetric Contour Maps and 

Calculation of Wetland Area and Stored Water 

Volume

A bathymetric data set of horizontal and vertical coordinates was created for each wetland. Each bathymetric data set 

included the data points collected within the perimeter of the 

wetland as well as the data points along the wetland perimeter. 

The software package SURFER was used to draw continuous 

contour lines by interpolation of the land-surface elevations 

using the kriging method (Keckler, 1997). Bathymetric contour 

maps were created at 0.5-ft contour intervals, with the exceptions of Duck Pond Marsh, which was relatively deep (1.0 ft 

intervals) and GS Marsh, which was relatively shallow (0.2 ft 

intervals). The contour intervals were chosen so that they were 

relevant to the scale of the topographic features in each wetland. The volume and area integration tools in SURFER were 

used to calculate wetland area and stored water volume for 

given stages (app. 2-11). Estimated area and volume were plotted as a function of stage for each wetland to compare stage and 

area, and to compare stage and volume.

Wetland bathymetry in this study was mapped using one 

of two approaches, and depending on wetland size, water depth, 

and density of trees, each approach generated different densities of bathymetric data points. Before comparing the area and 

volume estimates for the 10 wetlands, the potential effect of different bathymetric mapping approaches on wetland area and 

volume estimates was investigated at two wetland sites, GS 

Marsh and W-29 Marsh. These two wetlands were chosen for 

the comparison because they have shapes characteristic of the 

wetlands analyzed in this study: GS Marsh is nearly circular 

whereas W-29 Marsh has an elongated shape. In addition to the 

bathymetric maps originally generated at GS Marsh and W-29 

Marsh using the Topcon method, two additional bathymetric 

maps were generated for each of these two wetlands, based on 

two simpler approaches. The areas and volumes estimated at 

different stages by the two simpler approaches were compared 

to the Topcon approach, and results were used to infer the 

potential magnitude of errors from mapping approaches that 

use reduced densities of data points.

In the first of the simpler mapping approaches, the number 

of elevation data points collected with Topcon at the two wetlands was reduced until only three lines (transects) of data 

points remained at W-29 Marsh and two transects remained at 

GS Marsh. The density of topographic data points, in turn, was 

reduced from an average of 18.2 points per acre to 4.6 points 

per acre at W-29 Marsh, and from 61.9 points per acre to 12.5 

points per acre at GS Marsh. The new wetland bathymetry 

based on transect lines (and the known wetland perimeter) was 

interpreted using SURFER and the results were compared to 

the original Topcon mapping results.

In the second of the simpler mapping approaches, it was 

assumed that one other elevation contour is known in addition 

to the elevation of the wetland perimeter. This contour traces 

the outline of the inundated area at some stage intermediate to 

either full or dry. One elevation contour was selected for GS 

Marsh and for W-29 Marsh from the suite of contours developed from the Topcon mapping approach. This contour was 

added to simulate the additional bathymetric contour that could 

be determined in a wetland by mapping points along the edge of 

the flooded area with a DGPS unit.

Assessment of Wetland Vegetation 

Vegetation was assessed semiannually in all marsh and 

cypress wetland sites in May and October 2002, May and October 2003, and May 2004. At each wetland site, a transect line 

was established from the perimeter to the deepest point in the 

wetland. Three zones were established along the transect line 

and were defined as transition, intermediate, or deep based on 

their elevation relative to the elevation at the wetland perimeter. 

The transition zone was located 3-6 inches downslope from the 

elevation of the wetland perimeter (in marshes, 3-6 inches 

below the base of the palmetto fringe; in cypress wetlands, 3-6 

inches downslope from the normal pool elevation). The deep 

zone was located near a point of lowest elevation (maximum 

water depth) at each wetland. The intermediate zone was 

located at an elevation half-way between the deep zone elevation and the transition zone elevation. Elevations used to establish these zones were those surveyed by the SWFWMD. 

Three 9-square foot (ft2) fixed plots were established sideby-side perpendicular to the transect line in each of the three 

zones at each wetland. All plants visible within each plot were 

identified to species level and their percent cover was visually 

estimated. Water depth in each plot was recorded on each sampling date. An ancillary survey of Pinus elliotii (slash pine) 

trees also was made in January 2004 at W-29 Marsh because 

slash pines were present throughout this marsh during the study, 

but the fixed vegetation plots at W-29 Marsh did not include 

any tree species. The survey included data on location, water 

depth, tree diameter at breast height (dbh), and tree health 

(living/dead) of about 120 slash pine trees growing within the 

marsh.

Verification of species, when necessary, was provided by 

the University of South Florida Herbarium in Tampa, Florida. 

Plant names used in this report follow Wunderlin (1998). Plants 

are listed in vegetation tables if they provided at least 1 percent 

cover in at least one plot, and plants are highlighted as abundant 

if they provided at least 10 percent cover in at least one 

plot.Vegetation plots established in this study do not encompass 

all species present in each wetland and, therefore, cannot provide an exhaustive list of plant species present in each wetland. 

For example, plots in cypress wetlands rarely include tree species. Fixed plots, however, provide a consistent method to 

assess the vegetation community at known elevations, and to 

monitor changes in vegetation over time. 

Wetland plants were assigned a status (app. 12) based 

either on the Florida vegetative index (Florida Department of 

Environmental Protection, 2004) or the Atlas of Florida Vascular 
Bathymetry of Marsh and Cypress Wetlands 11

Plants (Wunderlin and Hansen, 2004). Any plant not specifically 

listed in the index is considered an upland plant with the exception 

of vines and aquatic plants. Aquatic plants are those, including 

the roots, that typically float on water or require water for their 

entire structural support, or they desiccate outside of water 

(Florida Department of State, 1994). The indicator categories 

are: Obligate wetland species (OBL); Facultative wetland 

species (FACW); and Facultative species (FAC). According 

to Federal guidelines (Reed, 1988), an OBL species is present 

in wetlands greater than 99 percent of the time; a FACW species is present in wetlands 67- 99 percent of the time; and a 

FAC species is present in wetlands 34-66 percent of the time. 

Although both OBL and FACW species are widely recognized 

as useful indicators of wetlands, FAC species can be dominant 

plants in uplands as well as in wetlands, and therefore, are not 

considered to be reliable indicators of wetlands. 

Bathymetry of Marsh and Cypress Wetlands

The surface area of the five marsh wetlands ranged from 

1.6 - 7.4 acres, with an average size of 4.6 acres (table 1). The 

surface area of the five cypress wetlands ranged from 1.3-8.8 

acres with an average of 3.9 acres. Generally, the smaller wetlands are shallower than the larger wetlands. For example, GS 

Marsh has an area of 1.6 acres and a maximum depth of 1.07 ft 

whereas W-03 Marsh has an area of 7.4 acres and a maximum 

depth of 5.44 ft. W-05 Cypress is an exception, however, 

because it has the largest surface area (8.8 acres) but an intermediate maximum depth of 2.11 ft. The relatively shallow 

depth at W-05 Cypress could be due in part to the thick layer of 

flocculent sediment that has accumulated on the floor of the 

wetland and filled in the deeper parts of the wetland basin.

 The bathymetric surveys indicate that 8 of the 10 wetlands 

in this study are shallow with a maximum depth of 3 ft or less 

(figs. 2A-11A). Two of the wetlands are deeper than 3 ft; Duck 

Pond Marsh has a maximum depth of 8.13 ft and W-03 Marsh 

has a maximum depth of 5.44 ft. At several of the sites, the maximum depth was in the bottom of a small isolated depression. An 

extreme example is at W-03 Marsh (fig. 8A), where the maximum 

depth was in a depression 3-ft deep with a surface area of only 

150 ft2. To avoid distorting the comparison of wetland depths 

caused by small but deep pits in a few wetlands, mean depth 

(total volume divided by total area) was used to compare wetland 

depths. The mean depth of the four marshes (excluding Duck 

Pond Marsh) ranged from 0.62-1.89 ft, with an average depth of 

1.16 ft (table 1). Duck Pond Marsh had the greatest mean depth 

of any wetland site (3.20 ft) and is not representative of the other 

marshes in this study. Mean depths of the cypress wetlands range 

from 0.46 to 1.08 ft, with an average depth of 0.69 ft. Data from 

the 10 wetlands in this study are not sufficient to determine 

whether these ranges of mean depths are representative of all the 

wetlands in the NTB area; however, it is noteworthy that the 

average mean depth of the four marshes (excluding Duck Pond 

Marsh) is nearly double that of the five cypress wetlands. 

Wetland-surface areas estimated in this study using DGPS 

were compared to wetland areas summarized in the National 

Wetlands Inventory (NWI) for 9 of the 10 study wetlands (app. 13). 

NWI maps produced by the U.S. Fish and Wildlife Service 

(FWS) use aerial photointerpretation to describe the location 

and extent of wetlands throughout the United States (U.S. Fish 

and Wildlife Service, 2004). NWI maps are used to delineate 

wetland boundaries, classify wetlands by type, and provide 

physical data including surface area. The NWI maps do not 

show all wetlands because maps are derived from aerial photointerpretation with varying limitations resulting from scale, 

wetland size, photo quality, inventory techniques, and other 

factors. These same limitations can cause wetland boundaries 

shown on the NWI maps to deviate from boundaries derived 

from ground surveys. 

Wetland-surface areas determined by the field methods 

used in this study were similar to the areas determined for these 

same wetlands by NWI photogrammetric interpretation of 7.5-

minute quadrangles, although some notable differences did 

occur. The area determined in this study for W-19 Cypress (2.1 

acres) was not directly comparable to a NWI area because W-19 

Cypress was not classified by the NWI as a small, isolated wetland, but instead as a part of a much larger wetland (20.9 acres). 

As a result, W-19 Cypress is not included in the comparison in 

appendix 13. If the surface-area estimates for the nine other 

wetlands are summed for each method, the total wetland area 

estimates are similar (USGS = 40.5 acres; NWI = 39.6 acres). 

Although the summed areas agreed closely, four of the marsh 

wetland area estimates differed by 25 to 35 percent. Surfacearea estimates for the five cypress wetlands and the remaining 

marsh wetland differed by 8 percent or less (app. 13). The FWS 

noted that wetland identification using NWI methods was particularly difficult when photography was captured during a dry 

year, whereas USGS methods used in this study are independent 

of short-term annual variations in rainfall and wetland water 

level (U.S. Fish and Wildlife Service, 2004). 

Stage-Area-Volume Relations for Marsh and

Cypress Wetlands

Stage typically is the most important if not the only hydrologic property monitored in wetlands. Hydrologic interpretations based on wetland stage require that the location and the 

elevation of the staff gage are accurately known. The locations 

of all staff gages found inside the 10 wetlands in this study are 

listed in appendix 1. The locations of the staff gages also are 

plotted on the bathymetric contour maps (figs. 2A-11A) to show 

the depth of the wetland at the staff gage locations. 
12 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 98.56 feet above

NGVD of 1929. Interval is 0.5 foot.

VEGETATION PLOTS

DEEPEST POINT – showing elevation in feet below

elevation of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where bathymetric

measurement made.

1.69

0

1

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

WETLAND STAGE, IN FEET ABOVE

NGVD OF 1929

1.0

0.8

0.6

0.4

0.2

0

96.5 97.0 97.5 98.0 98.5 99.0

2.0

1.5

1.0

0.5

0

Volume

Area

0 25 METERS

0 100 FEET

Bathymetric Data

Points

0 25 METERS

0 100 FEET

(A)

(B)

(C)

Green Swamp Cypress

EXPLANATION

Figure 3. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for Green Swamp Cypress.

8.13

0

2

4

6

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

WETLAND STAGE, IN FEET

ABOVE NGVD OF 1929

20

15

10

5

0

62 64 66 68 70 72

6

4

2

0

Volume

Area

Duck Pond Marsh

0 50 METERS

0 150 FEET

0 50 METERS

0 150 FEET

Bathymetric Data

Points

(A)

(B)

(C)

EXPLANATION

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 70.48 feet above

NGVD of 1929. Interval is 1 foot.

VEGETATION PLOTS

DEEPEST POINT – showing elevation in feet below

elevation of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where bathymetric

measurement made.

Figure 2. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for Duck Pond Marsh.
Stage-Area-Volume Relations for Marsh and Cypress Wetlands 13

2.65

0

1

1

0.5

1

1.5

1.5

1.5

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

WETLAND STAGE, IN FEET ABOVE

NGVD OF 1929

2.0

1.5

1.0

0.5

0

44 45 46 47

2.5

2.0

1.5

1.0

0.5

0

Volume

Area

Hillsborough River State Park Marsh

25 METERS

100 FEET

25 METERS

100 FEET

Bathymetric Data

Points

(A)

(B)

(C)

0

0

0.5

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 46.35 feet above

NGVD of 1929. Interval is 0.5 foot.

VEGETATION PLOTS

DEEPEST POINT – showing elevation in feet below

elevation of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where bathymetric

measurement made.

DITCH – with outflow elevation higher than elevation

of wetland perimeter.

EXPLANATION

0

0

Figure 5. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for Hillsborough River State Park Marsh.

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 93.30 feet above

NGVD of 1929. Interval is 0.2 foot.

VEGETATION PLOTS

DEEPEST POINT – showing elevation in

feet below elevation of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where

bathymetric measurement made.

1.07

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

WETLAND STAGE, IN FEET ABOVE

NGVD OF 1929

92.0 92.5 93.0 93.5

1.2

1.0

0.8

0.6

0.4

0.2

0

2.0

1.5

1.0

0.5

0

Volume

Area

Green Swamp Marsh

Bathymetric Data

Points

0 25 METERS

0 100 FEET

0

0 100 FEET

25 METERS

(A)

(B)

(C)

EXPLANATION

0

0

1.0

0.4

0.8

0.8 1.0

Figure 4. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for Green Swamp Marsh.
14 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

1.55

0

1

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

WETLAND STAGE, IN FEET ABOVE

NGVD OF 1929

5

4

3

2

1

0

42.0 42.5 43.0 43.5 44.0

6

4

2

0

Volume

Area

S-68 Cypress

50 METERS

150 FEET

50 METERS

150 FEET

Bathymetric Data

Points

(A)

(B)

(C)

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 43.66 feet above

NGVD of 1929 Interval is 0.5 foot

VEGETATION PLOTS

DEEPEST POINT – showing elevation in feet below

elevation of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where bathymetric

measurement made.

0

0

0

0

EXPLANATION

Figure 7. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for S-68 Cypress.

1.47

0

1

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

WETLAND STAGE, IN FEET ABOVE

NGVD OF 1929

0.8

0.6

0.4

0.2

0

40.5 41.0 41.5 42.0 42.5

1.5

1.0

0.5

0

Volume

Area

S-63 Cypress

25 METERS

100 FEET

0

100 FEET

Bathymetric Data

Points

(A)

(B)

(C)

0

0

EXPLANATION

0

25 METERS

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 42.32 feet above

NGVD of 1929. Interval is 0.5 foot.

VEGETATION PLOTS

DEEPEST POINT – showing elevation in

feet below elevation of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where

bathymetric measurement made.

Figure 6. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for S-63 Cypress.
Stage-Area-Volume Relations for Marsh and Cypress Wetlands 15

0

1

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

WETLAND STAGE, IN FEET ABOVE

NGVD OF 1929

5

4

3

2

1

0

69 70 71 72

10

8

6

4

2

0

Volume

Area

W-05 Cypress

50 METERS

150 FEET

50 METERS

150 FEET

Bathymetric Data

Points

(A)

(B)

(C)

BATHYMETRIC CONTOURS – Depth in feet below wetland

perimeter elevation of 71.47 feet above NGVD of 1929.

Interval is 0.5 foot

VEGETATION PLOTS

DEEPEST POINT – showing elevation in feet below elevation

of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where bathymetric

measurement made

DIRT ROADWAY – Elevation higher than wetland perimeter

elevation

WETLAND OUTFLOW – to roadside ditch at approximate

elevation of 71.0 feet above NGVD of 1929

0

0

EXPLANATION

0

0

2.11

Figure 9. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for W-05 Cypress.

5.44

0

1

2

0

2.5

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

15

10

5

0

67 68 69 70 71 72 73

8

6

4

2

0

Volume

Area

WETLAND STAGE, IN FEET ABOVE

NGVD OF 1929

W-03 Marsh

0 50 METERS

0 150 FEET

0 50 METERS

0 150 FEET

Bathymetric Data

Points

(A)

(B)

(C)

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 72.44 feet above

NGVD of 1929. Interval is 0.5 foot

VEGETATION PLOTS

DEEPEST POINT – showing elevation in feet below

elevation of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where bathymetric

measurement made

DITCH – with outflow elevation higher than elevation

of wetland perimeter.

EXPLANATION

Figure 8. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for W-03 Marsh.
16 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

2.76

0 1

2

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

10

8

6

4

2

0

67 68 69 70

8

6

4

2

0

Volume

Area

WETLAND STAGE, IN FEET ABOVE

NGVD OF 1929

W-29 Marsh

50 METERS

150 FEET

0

150 FEET

Bathymetric Data

Points

(A)

(B)

(C)

0

0

0

50 METERS

BATHYMETRIC CONTOURS – Depth in feet below wetland

perimeter elevation of 69.92 feet above NGVD of 1929.

Interval is 0.5 foot

VEGETATION PLOTS

DEEPEST POINT – showing elevation in feet below

elevation of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where bathymetric

measurement made

DIRT ROADWAY – Wetland outflow at an elevation higher

than elevation of wetland perimeter

EXPLANATION

Figure 11. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for W-29 Marsh.

2.70

0 1

2

VOLUME,

IN ACRE-FEET

AREA, IN ACRES

WETLAND STAGE, IN FEET ABOVE

NGVD OF 1929

2.5

2.0

1.5

1.0

0.5

0

60.5 61.5 62.5 63.5

Volume

Area

W-19 Cypress

50 METERS

150 FEET

0 50 METERS

0 150 FEET

Bathymetric Data

Points

(A)

(B)

(C)

BATHYMETRIC CONTOURS – Depth in feet below

wetland perimeter elevation of 63.23 feet above

NGVD of 1929. Interval is 0.5 foot

VEGETATION PLOTS

DEEPEST POINT – showing elevation in feet below

elevation of wetland perimeter

STAFF LOCATION

BATHYMETRIC POINT – Location where bathymetric

measurement made

0

0

EXPLANATION

2.5

2.0

1.5

1.0

0.5

0

Figure 10. (A) Wetland bathymetric contours, (B) density of bathymetric data points, and (C) stage-volume and stage-area 

curves for W-19 Cypress.
Potential Effects of Bathymetric Mapping Approach on Stage-Area and Stage-Volume Relations 17

Ideally, a staff gage would be located at the deepest point 

in the deepest part of a radially symmetrical basin, in order to 

accurately describe the wetland as dry when the staff gage is 

dry. Many wetlands, however, are not radially symmetrical 

even though they commonly originate as subsidence features, 

and actual staff gage locations are not always ideal. Without 

bathymetric data, improperly placed staff gages can go unrecognized. For example, at W-29 Marsh (fig. 11A) the bathymetric map indicates that the wetland has two distinct basins. The 

original staff gage was not located at the deepest point in the 

wetland, and the longest historical record of stage at W-29 

Marsh was collected from a staff gage located in the shallower 

(or higher) of the two basins. The land-surface elevation at this 

original staff gage is 68.00 ft above NGVD of 1929. For this 

study a second staff gage and a continuous stage recorder were 

installed in the lower (or deeper) basin at a land-surface elevation of 67.30 ft above NGVD of 1929. The elevation of the lowest point measured during collection of bathymetric data at 

W-29 Marsh was 67.20 ft above NGVD of 1929. When the 

original staff gage at the higher elevation was used to determine 

stage, the wetland was commonly described as dry (0 percent 

inundation), when in reality the area inundated at W-29 Marsh 

could have ranged from 0 to 2.4 acres (app. 11).

Conversely, a bias results if the staff gage is located in an 

uncharacteristically deep hole in the lowest part of a wetland. 

Small deep holes are common in wetlands. They may be subsidence features or they may be dug by feral hogs or other 

animals that use wetlands as feeding areas, watering holes, or 

breeding grounds. The staff gage is not located in the small, 

deep hole at W-03 Marsh; however if it was, a water depth of 

2 ft would inundate less than 1 percent of the wetland-surface 

area. Although it is not possible to retroactively optimize the 

location of staff gages that have been used to collect historical 

data, a thorough knowledge of bathymetry allows for a much 

more accurate interpretation of available stage data.

Bathymetric data were used to summarize the relations 

between stage and area, and stage and volume for each of the 

wetlands in this study (figs. 2C-11C). The plots of stage-areavolume and the bathymetric maps indicate that the inundated 

surface area and stored water volume can change substantially 

over a relatively small increment of stage. In general, stage-area 

curves show the largest incremental changes in wetland area at 

lower stages. This pattern occurs because the relatively flat 

bottom of most of the wetlands causes a large increase in 

wetted area with a small increase in wetland stage. In contrast, 

the stage-volume curves show a slow increase in volume at 

lower stages because the increased area does not contribute to 

much increase in volume. W-03 Marsh is an exception to this 

pattern because it has one small depression about 3-ft deep in 

an otherwise flat wetland bottom. Thus, at low stages, a small 

increase in surface area results from a relatively large increase 

in water volume at W-03 Marsh (fig. 8C). 

At higher wetland stages, as the flooded area approaches 

the perimeter (near 100 percent inundation), a large increase in 

wetland volume is required to produce a relatively small 

increase in surface area. For example, adding 3.0 acre-feet 

(acre-ft) of water to W-29 Marsh when it is dry (assuming 

no leakage losses or evaporation) would inundate 4.1 acres, or 

63 percent of the total surface area (app. 11). An additional 3.0 

acre-ft of water would inundate only 1.2 acres more, or 18 percent 

of the total surface area.

Hayashi and van der Kamp (2000) developed power 

functions to describe wetland area and stage for small wetlands in 

isolated and smoothly sloped depressions in the prairie pothole 

region of North America. This approach failed, however, when 

applied to the wetlands in this study (data not shown), because 

most of the 10 wetlands are not radially symmetrical, and they 

lack regularly sloping sides and a parabolic shape. Instead, several 

of the wetlands in this study have irregular shapes, and wetland 

bottoms have distinct breaks in slope from a relatively flat central 

area to steep sloped edges. Thus, the resulting stage-area curves 

for the 10 study wetlands had an S-shaped appearance so that wetland area could not be accurately represented over the entire range 

in stage by power functions or higher-order polynomials.

Ditches into wetlands or roadways intersecting the perimeter of wetlands can change the stage-area-volume relations by 

lowering the stage at which outflow begins to occur. For example at W-05 Cypress (fig. 9A), a roadway and the ditches flanking the roadway intersect the wetland perimeter causing outflow 

at an elevation that is lower than the palmetto fringe elevation 

of 71.47 ft above NGVD of 1929. When the stage reaches 71.0 ft 

above NGVD of 1929 at W-05 Cypress, outflow to a ditch adjacent to the road occurs. At a stage of 71.3 ft above NGVD of 

1929, outflow from the ditch flows south along the road and discharges into a nearby wetland. The “functioning perimeter” at 

W-05 Cypress likely occurs at an elevation between 71.0 and 

71.3 ft above NGVD of 1929, corresponding to an effective 

inundated area of between 4.9 and 7.2 acres, respectively. It is 

unlikely that the inundated area of W-05 Cypress reaches the 

entire 8.8 acres encompassed by the palmetto fringe. Although 

HRSP Marsh (fig. 5A) and W-03 Marsh (fig. 8A) have outflow 

ditches, and W-29 Marsh (fig. 11A) has an intersecting roadway, the elevation of these ditches and the roadway are at or 

above the perimeter elevation, and do not reduce the effective 

total wetland area at these sites. Although areas of naturally 

occurring outflow were identified during the study (see figs. 

2A-11A), for the purposes of this report stage-area and stagevolume curves assumed no outflow or inflow below the palmetto fringe. The practical use of these curves for the estimation 

of water budgets, however, would necessitate consideration of 

any such inflows or outflows. 

Potential Effects of Bathymetric Mapping 

Approach on Stage-Area and Stage-Volume 

Relations

The error introduced by creating bathymetric maps from a 

lower density of data points was estimated by comparing the 

original stage-area and stage-volume curves for W-29 Marsh 

and GS Marsh to those created from the two reduced-density 
18 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

data sets. The maps created from a low density of data points 

lost information about the non-linearity of the basin topography. Fewer data points resulted in a more linear interpolation of 

the elevation between data points than actually existed. The 

resulting bathymetric maps generated from a lower density of 

data points can look convincing, but a comparison to maps created from a high density of data points collected at the same site 

clearly shows the differences (figs. 12A-C, 13A-C). 

At W-29 Marsh, the data set using transect data alone provided a low density of bathymetric points in the area between the 

two circular basins of the marsh (fig. 12). This is the area of the 

wetland where the bottom is relatively flat. Within this middle 

range of stage (67.50-69.00 ft above NGVD of 1929) there is a 

large increase in inundated area associated with a small change in 

stage. Linear interpolation of the transect data alone tended to 

decrease the estimate of flooded area at intermediate water levels. 

0

A) All bathymetric data points B)

ransect

Bathymetric data points along

three t lines

100 METERS

W-29 Marsh

EXPLANATION

DEPTH, IN FEET

0-0.5

0.5-1.0

1.0-1.5

1.5-2.0

2.0-2.5

>2.5

WETLAND PERIMETER AT 100 PERCENT

INUNDATION

WETLAND PERIMETER AT A SELECTED WETLAND

STAGE BELOW 100 PERCENT INUNDATION

CONTOUR LINE GENERATED BY SURFER

BATHYMETRIC DATA POINT

0 150 300 FEET

50

C Bathymetric data points along

three t line and a contour

line

)

ransect s

Figure 12. Contour lines developed for W-29 Marsh from (A) all bathymetric data points, (B) a subset of bathymetric data points along 

three transect lines, and (C) a subset of bathymetric data points along three transect lines and a contour line.
Potential Effects of Bathymetric Mapping Approach on Stage-Area and Stage-Volume Relations 19

Green Swamp Marsh

EXPLANATION

DEPTH, IN FEET

0-0.2

0.2-0.4

0.4-0.6

0.6-0.8

0.8-1.0

>1.0

WETLAND PERIMETER AT 100 PERCENT

INUNDATION

WETLAND PERIMETER AT A SELECTED WETLAND

STAGE BELOW 100 PERCENT INUNDATION

CONTOUR LINE GENERATED BY SURFER

BATHYMETRIC DATA POINT

0 25

0 100

50 METERS

200 FEET

A) All bathymetric data points B)

ransect

Bathymetric data points along

two t lines

C Bathymetric data points along

two t line and a

contour line

)

ransect s

For both W-29 Marsh and GS Marsh, transect data alone 

predicted substantially less flooded area at most values of stage. 

For example, at W-29 Marsh, the estimated flooded area at a 

stage of 68.02 ft was 1.22 acres (fig. 14A) based on the transect 

data alone, or about 49 percent less than the 2.41 acres of 

flooded area predicted at the same stage by using the complete 

data set. At GS Marsh, the estimated flooded area at a stage of 

92.60 ft was 0.54 acres (fig. 15A) based on the transect data 

alone, or about 40 percent less than the 0.90 acres of flooded 

area predicted using the complete data set. Flooded area was 

slightly overpredicted by the transect approach at GS Marsh at 

higher stage because there is an area inside the wetland perimeter with an elevation higher than the palmetto fringe. This area 

was not described accurately by the transect data, causing an 

upward shift in the stage-area curve.

Figure 13. Contour lines developed for Green Swamp Marsh from (A) all bathymetric data points, (B) a subset of bathymetric data points 

along two transect lines, and (C) a subset of bathymetric data points along two transect lines and a contour line.
20 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

67 68 69 70 67.5 68.5 69.5

67 68 69 70 67.5 68.5 69.5

7

6

5

4

3

2

1

0

AREA, IN ACRES

Three transects

Three transects plus 68.1-foot contour

Complete data set

WETLAND STAGE, IN FEET ABOVE NGVD OF 1929

(A) W-29 Marsh

WETLAND STAGE, IN FEET ABOVE NGVD OF 1929

VOLUME, IN ACRE-FEET

10

9

8

7

6

5

4

3

2

1

0

Three transects

Three transects plus 68.1-foot contour

Complete data set

(B) W-29 Marsh

The percent error in the flooded-area estimates made using 

transect data alone increased as the flooded area became 

smaller at both wetlands, particularly at GS Marsh. For example, when the flooded area at GS Marsh was 0.25 acres, the 

transect approach (fig. 13B) estimated the flooded area at 0.02 

acres or 92 percent less than the estimate using the complete 

data set. The increase in error occurred because as total area 

decreases, discrepancies in area estimates become proportionally larger. Moreover, the transect data sets were more likely to 

exclude the lowest elevation in the wetland. At GS Marsh, the 

minimum elevation used in the transect data set was 92.33 ft 

above NGVD of 1929. The lowest elevation used in the complete data set was 92.25 ft above NGVD of 1929. At W-29 

Marsh, the transects traversed the deepest point in the wetland 

so the lowest elevation value in both the transect data set and the 

complete data set was the same. In contrast, the elevation of the 

wetland perimeter, or highest stage, and its location were determined independently of the bathymetric mapping and were consistent at a given wetland regardless of the mapping approach. 

For this reason, the values of predicted area tended to converge 

for all approaches as the stage approached 100 percent full 

(figs. 14A-15A). 

Adding one elevation contour to the transect data sets 

greatly improved the accuracy of the flooded-area predictions 

for both wetland shapes, but flooded-area predictions made 

with transects and a contour line still tended to be lower than 

Figure 14. Effects of a reduced density of bathymetric data points at 

W-29 Marsh on (A) stage-area and (B) stage-volume relations.

The center of W-29 Marsh supports blue 

maidencane, dog fennel, and broomsedge 

bluestem during a prolonged period of low water 

levels.
Potential Effects of Bathymetric Mapping Approach on Stage-Area and Stage-Volume Relations 21

92 92.4 92.8 93.4 92.2 92.6 93

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

AREA, IN ACRES

Two transects

Two transects plus 92.7-foot contour

Complete data set

WETLAND STAGE, IN FEET ABOVE NGVD OF 1929

(A) Green Swamp Marsh

WETLAND STAGE, IN FEET ABOVE NGVD OF 1929

VOLUME, IN ACRE-FEET

1.2

1.0

0.8

0.6

0.4

0.2

0

Two transects

Two transects plus 92.7-foot contour

Complete data set

(B) Green Swamp Marsh

93.2

92 92.4 92.8 93.4 92.2 93.2 92.6 93

those made using the complete data set. Contours added inside 

the wetland perimeters of W-29 Marsh (fig.12C) and GS Marsh 

(fig. 13C) denoted the outline of the flooded area at an intermediate stage below the perimeter. For example, at W-29 Marsh, 

a contour line was added at 68.10 ft above NGVD of 1929.

The addition of this contour reduced the error in flooded-area 

estimates at a stage of 68.02 ft above NGVD of 1929 from 

49 percent to 16 percent (fig. 14A). At GS Marsh, the contour 

was added at 92.70 ft above NGVD of 1929. The addition of 

this contour decreased the error in the estimated flooded area at 

a stage of 92.60 ft from 40 percent to about 16 percent (fig. 

15A). The added contours tended to make the most improvement in the estimated areas at stage values equal to or greater 

than the elevation of the added contour. 

 At both wetlands, the simple mapping approach using 

transect data alone tended to predict substantially less wetland 

volume at a given stage than using the complete data set 

obtained from the Topcon mapping approach (fig. 14B, 15B). 

At W-29 Marsh, the wetland volume estimated at a stage of 

68.02 ft using the complete data set was 0.66 acre-ft. The wetland volume estimated using transect data alone was 0.40 acre-ft 

(about 39 percent less), and the volume estimated from the 

transect data with the contour line was 0.47 acre-ft (about 28 

percent less). Filling the wetland to the perimeter required a 

water volume of 9.42 acre-ft, based on data obtained from the 

Topcon mapping approach. The volume estimated using 

transect data alone was about 20 percent less (7.69 acre-ft), 

whereas the volume estimated using the transect data and the 

The center of Green Swamp Marsh supports 

maidencane, pickerelweed, and other obligate 

wetlands plants.

Figure 15. Effects of a reduced density of bathymetric data points at Green 

Swamp Marsh on (A) stage-area and (B) stage-volume relations.
22 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

(B) W-29 Marsh

(A) Green Swamp Marsh

WEEKLY AVERAGE FLOODED AREA

(PERCENT OF FULL)

WEEKLY AVERAGE FLOODED AREA

(PERCENT OF FULL)

100

80

60

40

20

0

100

80

60

40

20

0

Original data

Transects only

Transects plus contour

Original data

Transects only

Transects plus contour

Oct Dec Jan Feb Mar Apr May June July Aug Sept Nov

2001 2002

Oct Dec Jan Feb Mar Apr May June July Aug Sept Nov

2001 2002

additional contour line was 9.03 acre-ft (4 percent less). Similarly at GS Marsh, the discrepancies in estimated wetland volume were greatest using the transect data alone. The differences 

in estimated wetland volume between the complete data set and 

the other two data sets were greatest at smaller wetland volumes and were reduced as the wetland volume approached 100 

percent inundation. The addition of a contour to the transect 

data method greatly improved the accuracy of wetland volume 

estimates. For example, when GS Marsh is full, the wetland 

holds a volume of 1.01 acre-ft based the data obtained from the 

Topcon mapping approach. Using transect data with an additional contour line provided an approximation within 5 percent 

of this volume (0.96 acre-ft), whereas the transect data alone 

underestimated the volume by about 20 percent (0.80 acre-ft).

Twelve months of daily stage data were analyzed using 

the three different stage-area relations developed for W-29 

Marsh and GS Marsh. The weekly average percent area of 

inundation was plotted for the two sites (fig. 16A,B). The 

weekly average flooded areas estimated using the complete data 

sets are shown as vertical bars in figure 16. The estimates of 

flooded areas derived from the two simpler mapping 

approaches using data sets with fewer points also are shown for 

comparison. 

Plots of the weekly average flooded area using the complete data sets (fig. 16) also highlight differences in the amount 

of flooded area occurring in the two wetlands during the same 

period of time (October 2001 - September 2002). At GS Marsh, 

which has not been affected by human activities, more than 60 

percent of the wetland area was inundated for about 9 months of 

the year (fig. 16A). In contrast at W-29 Marsh, which has been 

affected by well field development, about 50 percent of the wetland was inundated for about 2 months of the year, and the 

entire wetland was dry for more than 8 months of the year 

(fig. 16B).

Figure 16. Changes in weekly average flooded area over time at Green Swamp Marsh and W-29 

Marsh.
Relative Abundance of Wetland Plants in Fixed Plots 23

Relative Abundance of Wetland Plants in 

Fixed Plots

In all 10 wetlands, vegetation growing in deep, intermediate, 

and transition plots was assessed semiannually from May 2002 

to May 2004. Wetland water levels in May 2002 were distinctly 

lower than wetland water levels measured in the subsequent 

four assessments. Two factors most likely were responsible for 

the unanticipated water-level differences: rainfall amounts and 

the volume of ground-water withdrawal in well fields. During 

2000-2002, rainfall in the west-central part of Florida was 

below average (Southwest Florida Water Management District, 

2003b). During the latter part of 2002 and continuing through 

2004, however, rainfall was above average (Southwest Florida 

Water Management District, 2003b). Moreover, with regard to 

the four wetlands located on the Cypress Creek well field (W-03 

Marsh, W-05 Cypress, W-19 Cypress, and W-29 Marsh), 

there were effects on wetland water levels from a reduction in 

ground-water withdrawal rates beginning in 2003 (Tampa Bay 

Water, 2003). All of these conditions were reflected in the vegetation in the wetlands. Therefore, results of the initial vegetation assessment made during May 2002 (henceforth referred to 

as the “dry period”) are reported separately, and results of the 

other four semiannual assessments (October 2002, May 2003, 

October 2003, and May 2004) (referred to as the “wet period”) 

are combined and reported together in the vegetation tables. 

The five semiannual vegetation assessments completed 

during this study produced lists of wetland plant species found 

in the 15 fixed plots at known elevations in each of the 10 wetlands. Although these lists are not exhaustive, the most common species found in this study have also been reported 

previously in these wetlands by the SWFWMD, Tampa Bay 

Water, and others during the previous one to two decades of 

periodic routine vegetation monitoring in well fields, parks, and 

other public areas in the NTB area (Rochow, 1994; Berryman 

and Henigar, 2001; Biological Research Associates, Inc., 2001; 

Reynolds, Smith & Hills, Inc., 2001). SWFWMD in conjunction with Tampa Bay Water developed a Wetlands Assessment 

Procedure (WAP) in 1999 (Tampa Bay Water, 2000) to monitor ecological changes in a large number of wetlands in the 

NTB area. One component of the WAP, which currently is in 

use in more than 500 wetlands, evaluates vegetation trends by 

periodically assessing the percent cover, composition, and 

zonation of ground cover, shrubs, and trees along a transect line 

in each target wetland. Vegetation documented by SWFWMD 

in WAP evaluations during 2003 in the 10 wetlands described 

in this report is similar to vegetation found in USGS fixed plots 

in 2003 (Ted Rochow, SWFWMD, written commun., 2004). 

Natural Marsh Wetlands 

GS Marsh (fig. 4) and HRSP Marsh (fig. 5) are small 

isolated natural marsh wetlands that are similar to each other in 

basin size, shape, and bathymetry, and their surface-water levels have remained largely unaffected by human activities. Both 

wetlands typically are dry during the late-winter and spring, and 

the Serenoa repens (palmetto) fringe is well developed. The 

plant communities in these marshes consist primarily of OBL 

and FACW native wetland plants, which are well-adapted to the 

natural hydrologic regime. Continuous vegetation monitoring 

during 1977-1982 indicated that there was little or no terrestrial 

plant invasion at HRSP Marsh (Lopez, 1983), and more recent 

annual monitoring confirms these observations (Ted Rochow, 

SWFWMD, oral commun., 2002). There is a small, naturally 

occurring knoll near the center of HRSP Marsh where the elevation is slightly higher than the surrounding marsh, and where 

Acer rubrum (FACW) became established beginning in the 

1970s (Mumme, 1978; Lopez, 1980).

In May 2002, deep plots in both wetlands contained no 

standing water, although the soil was saturated. Panicum hemitomon (OBL), the dominant plant, covered 25-50 percent of deep 

plots in both wetlands. Pontederia cordata (OBL) also was abundant in the deep plots at HRSP Marsh. Soils in intermediate plots 

of both wetlands were saturated to dry. Panicum hemitomon 

(OBL) and Eriocaulon compressum (OBL) were abundant in 

intermediate plots at GS Marsh, whereas Amphicarpum muhlenbergianum (FACW) and Rhynchospora inundata (OBL) were 

abundant in intermediate plots at HRSP Marsh. In transition plots 

at both sites, Amphicarpum muhlenbergianum (FACW) was 

abundant (tables 4A, 5A). 

During the wet period, water depths were very similar 

in deep plots at both natural wetlands (about 8-12 inches). 

Abundant vegetation in deep plots at both sites (tables 4B, 5B) 

included the OBL species Panicum hemitomon, Pontederia 

cordata, Utricularia purpurea (at GS Marsh), and U. foliosa

(at HRSP Marsh) (tables 4B, 5B). In intermediate and transition 

plots, water depth tended to be greater at GS Marsh than at 

HRSP Marsh during the wet period. Nearly all species found in 

intermediate plots at GS Marsh in the wet period were OBL 

plants, whereas plants in intermediate plots at HRSP included a 

mixture of OBL and FACW plants. The plant communities 

found in transition plots at both sites during October 2002 - May 

2004 included a mixture of FAC, FACW, and OBL species.

Impaired Marsh Wetland 

W-29 Marsh (fig. 11) is a relatively large, shallow marsh 

wetland located in the Cypress Creek Well Field. The marsh 

water-level regime reflects the ambient climate coupled with 

the cumulative effects of 25 years of ground-water pumping in 

the well field. The palmetto fringe is evident around much of the 

wetland perimeter. Water levels in the marsh have declined 

since 1979 when the well field achieved full-scale production 

(Reynolds, Smith & Hills, Inc., 2001). Utricularia sp., 

Nymphoides sp., and other submersed and floating species

declined in abundance soon after well-field production began 

and were replaced by emergent rushes and sedges. Amphicarpum muhlenbergianum and Hypericum myrtifolium were common in the marsh during the 1980s; encroachment by 

Andropogon sp. has occurred since 1995 (Reynolds, Smith & 

Hills, Inc., 2001). 
24 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

Table 4. Vegetation in fixed plots in Green Swamp Marsh.

[Shaded species make up 10 percent or more of the vegetation cover in a plot]

Depth below land-surface elevation at palmetto fringe1

Transitional plots

0-0.5 feet

Intermediate plots

0.5-1.0 feet

Deep plots

1.0-2.0 feet

A. May 2002

Amphicarpum muhlenbergianum (FACW) Carex joorii (FACW) Panicum hemitomon (OBL)

Andropogon vivginicus (FAC) Eriocaulon compressum (OBL)

Lachnanthes caroliana (FAC) Panicum hemitomon (OBL)

Proserpinaca pectinata (OBL) Proserpinaca pectinata (OBL)

Xyris fimbriata (OBL) Xyris fimbriata (OBL)

B. October 2002, May 2003, October 2003, and May 2004

Amphicarpum muhlenbergianum (FACW) Carex verrucosa (FACW) Carex verrucosa (FACW)

Andropogon virginicus (FAC) Eriocaulon compressum (OBL) Panicum hemitomon (OBL)

Lachnanthes caroliana (FAC) Panicum hemitomon (OBL) Pontederia cordata (OBL)

Panicum hemitomon (OBL) Proserpinaca pectinata (OBL) Utricularia purpurea (OBL)

Proserpinaca pectinata (OBL) Saccharum giganteum (OBL)

Rhynchospora cephalantha (OBL) Utricularia purpurea (OBL)

Sagittaria graminea (OBL)

Utricularia purpurea (OBL)

Xyris fimbriata (OBL)

193.30 feet above NGVD of 1929.

Table 5. Vegetation in fixed plots in Hillsborough River State Park Marsh.

[Shaded species make up 10 percent or more of the vegetation cover in a plot; >, greater than]

Depth below land-surface elevation at palmetto fringe1

Transitional plots

0-0.5 feet

Intermediate plots

0.5-1.0 feet

Deep plots

>1.0 feet

A. May 2002

Amphicarpum muhlenbergianum (FACW) Amphicarpum muhlenbergianum (FACW) Panicum hemitomon (OBL)

Andropogon virginicus (FAC) Polygonum hydropiperoides (OBL) Pontederia cordata (OBL)

Panicum hemitomon (OBL) Rhynchospora inundata (OBL)

Pluchea rosea (FACW)

B. October 2002, May 2003, October 2003, and May 

2004

Amphicarpum muhlenbergianum (FACW) Amphicarpum muhlenbergianum (FACW) Panicum hemitomon (OBL)

Andropogon virginicus (FAC) Leersia hexandra (OBL) Pontederia cordata (OBL)

Juncus maiginatus (FACW) Oxypolis filiformis (OBL) Utricularia foliosa (OBL)

Leersia hexandra (OBL) Panicum verrucosum (FACW)

Ludwigia linearis (OBL) Polygonum hydropiperoides (OBL)

Panicum hemitomon (OBL) Proserpinaca pectinata (OBL)

Panicum verrucosum (FACW) Rhynchospora inundata (OBL)

Panicum virgatum (FACW) Sagittaria graminea (OBL)

Pluchea rosea (FACW) Scleria baldwinii (FACW)

Polygonum hydropiperoides (OBL) Utricularia foliosa (OBL)

146.35 feet above NGVD of 1929.
Relative Abundance of Wetland Plants in Fixed Plots 25

During May 2002, the entire wetland was dry, and vegetation was not similar to vegetation in any of the other marsh 

sites. In the deep plots, Eupatorium capillifolium (FAC) and

dead stands of Panicum hemitomon (OBL) were abundant. The 

plant community in the intermediate plots consisted of an 

upland species (Conyza canadensis) and several abundant 

FACW and FAC species including Amphicarpum muhlenbergianum, Eupatorium capillifolium, and Andropogon virginicus, 

which was the only plant present in transition plots (table 6A).

Heavy rains during the autumn of 2002 and during much 

of 2003 inundated the deep and intermediate plots at W-29 

Marsh, and OBL and FACW species were evident in subsequent vegetation assessments, presumably regrowing from the 

seed bank in the substrate (Brock and others, 2003). Water 

depths ranged from 24 inches in May 2003 to 36 inches in 

October 2003 in deep plots, where Panicum hemitomon (OBL)

and Nymphaea odorata (OBL) were abundant (table 6B). 

Water depth in intermediate plots ranged from 12 inches (May 

2003) to 26 inches (October 2003). Abundant plants included 

Euthamia caroliniana (FAC), Eupatorium capillifolium

(FAC), Hypericum fasiculatum (OBL), Panicum hemitomon

(OBL), Sagittaria graminea (OBL), and Utricularia purpurea

(OBL). Transition plots had 2-3 inches of water in May 2003, 

4-8 inches of water in October 2003, and were dry in May 2004. 

The most abundant plants in these plots during 2003 included 

Panicum hemitomon (OBL) and Xyris fimbriata (OBL).

There has been an incursion of Pinus elliottii (slash pines)

(upland) at W-29 Marsh. Photographs taken annually beginning 

in 1985 (Ted Rochow, SWFWMD, written commun., 2003) 

indicate that the slash pines began to appear sometime between 

1991 and 1995, when conditions were dry. These slash pines 

presumably were seeded from slash pines in the surrounding 

landscape, and they became distributed throughout the marsh 

by 1998 (fig. 17). Although none of the slash pines were located 

in the vegetation plots established at the site, field observations 

during May 2002 - October 2003 (the wet period) indicate that 

most of the slash pine trees in the marsh had died. Wet conditions are stressful to young slash pines (less than 10 years old), 

and the slash pines in W-29 Marsh appeared to have died in 

response to inundation from the higher water levels, which 

began to occur during late 2002. Field data collected in January - 

February 2004 indicate that the slash pine trees ranged in size 

from 0.78 inches dbh to 12.20 inches dbh, with an average dbh 

of 4.7 inches. As of that date, all slash pines growing at or below 

an elevation of 68.42 ft above NGVD of 1929 were dead. Of the 

nearly 120 trees assessed at the site growing at or below the 

palmetto fringe elevation (69.92 ft above NGVD of 1929), only 

12 percent were still alive in January - February 2004. 

Table 6. Vegetation in fixed plots in W-29 Marsh.

[Shaded species make up 10 percent or more of the vegetation cover in a plot; >, greater than]

Depth below land-surface elevation at palmetto fringe1

Transitional plots

0-1.0 feet

Intermediate plots

1.0-2.0 feet

Deep plots

>2.0 feet

A. May 2002

Andropogon virginicus (FAC) Amphicarpum muhlenbergianum (FACW) Andropogon virginicus (FAC)

Andropogon virginicus (FAC) Eupatorium capillifolium (FAC)

Conyza canadensis (upland) Panicum hemitomon (OBL)

Eupatorium capillifolium (FAC)

Panicum hemitomon (OBL)

B. October 2002, May 2003, October 2003, and May 2004

Amphicarpum muhlenbergianum (FACW) Amphicarpum muhlenbergianum (FACW) Nymphaea odorata (OBL)

Andropogon virginicus var. glaucus (FAC) Andropogon virginicus (FAC) Panicum hemitomon (OBL)

Panicum hemitomon (OBL) Eupatorium capillifolium (FAC)

Utricularia purpurea (OBL) Euthamia caroliniana (FAC)

Xyris fimbriata (OBL) Hypericum fasciculatum (OBL)

Lachnanthes carolina (FAC)

Panicum hemitomon (OBL)

Rhynchospora microcarpa (OBL)

Saccharum baldwinii (OBL)

Sagittaria graminea (OBL)

Utricularia purpurea (OBL)

169.92 feet above NGVD of 1929.
26 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

W-29 Marsh

BATHYMETRIC CONTOURS – Depth in

feet below normal pool elevation of

69.92 feet above NGVD of 1929.

Interval is 0.5 foot

LOCATION OF DEAD –

LOCATION OF LIVING –

Pinus elliotii

Pinus elliotii

EXPLANATION

0

0.5 1

1.5

2

2.5

2.5

Augmented Marsh Wetlands 

W-03 (fig. 8) is a shallow, augmented marsh wetland with 

a small and relatively deep area that is inundated year-round. 

Before well-field operation began in 1976, W-03 Marsh contained a variety of broad-leaf emergent and floating wetland 

plants (Reynolds, Smith & Hills, Inc., 2001). Soon after production began in 1976, water levels in the wetland declined and wetland soils became dry and fissured. Grasses and woody species 

quickly invaded the site (Reynolds, Smith & Hills, Inc., 2001). 

Augmentation of W-03 Marsh with ground water began in 1978. 

Although water levels have varied, the marsh has never been 

allowed to dry out completely and a thick layer of partially 

decomposed vegetation (muck) has developed. Although water 

is below land surface throughout much of the marsh for many 

months each year, the thick organic muck substrate remains 

saturated and wetland vegetation is dense throughout those areas. 

Periphyton (attached algae) is abundant on aquatic plant stems 

and on the decomposing vegetation when water is in the marsh. 

There are several areas covered with Typha latifolia (OBL) 

across the western part of the wetland, and isolated stands of

Salix carolinana (OBL) in the southern part of the wetland. 

Recent monitoring indicates that Typha latifolia is increasing its 

areal coverage (Reynolds, Smith & Hills, Inc., 2001). Acer 

rubrum (FACW) is encroaching in several areas, particularly 

along the eastern edge of the wetland.

In May 2002 (the dry period), water depth was 8-10 inches 

in deep plots, and much of the western part of the wetland had 

no water at land surface. The plant community in deep plots 

included OBL species similar to those found in the natural 

marshes (Panicum hemitomon, Sagittaria latifolia, and Nymphaea odorata) (table 7A). Intermediate plots were saturated 

(no standing water) and abundant OBL species included Sagittaria latifolia and Panicum hemitomon. In transition plots along 

the shallow margins of the wetland, Callicarpa americana

(upland) was abundant. Numerous FAC species and the vine 

Berchemia scandens contributed to the dense foliage cover. 

Figure 17. Distribution and status of Pinus elliotii trees in W-29 Marsh during January-February, 2004.

An 18-month period of high water at W-29 Marsh 

caused the death of slash pines that had encroached 

during more than 10 years of low water.
Relative Abundance of Wetland Plants in Fixed Plots 27

Water levels in W-03 were much deeper during the wet 

period (October 2002 - May 2004) than during the previous dry 

period. In October 2003, water depths were 26-34 inches in the 

deep plots, and 15-17 inches in the intermediate plots. The plant 

community in deep and intermediate plots, however, consisted 

of OBL species, and did not change appreciably from what was 

found in May 2002. The soil in the transition plots was dry in 

May 2004, and despite wetter weather the plant community was 

similar to that found in May 2002. 

Duck Pond Marsh (fig. 2) is a deep (mean depth 3.20 ft), 

augmented marsh wetland located in the Cross Bar Ranch Well 

Field. There is no palmetto fringe because of past and present 

land-management practices. The well field was constructed in 

1979 and ground-water withdrawal for public supply began in 

1980. Before ground-water withdrawal, Duck Pond Marsh contained a variety of broad-leaf emergent and floating wetland 

plants (Biological Research Associates, Inc., 2001). Augmentation of Duck Pond Marsh with ground water began in 1987. 

Since 1997, the marsh water level has typically been kept 

between 67.2 and 70.4 ft above NGVD of 1929, providing 

continuous inundation of 45-98 percent of the wetland in order 

to provide year-round wildlife habitat in the well field (Dave 

Slonena, Pinellas County, written commun., 2004). Duck Pond 

Marsh does not have Panicum hemitomon (a characteristic 

marsh species) in the deep plots because of its uniformly greater 

depth compared to the natural marshes in this study. A thick 

layer of unconsolidated, partially decomposed vegetation has 

accumulated on the wetland bottom since augmentation began. 

Periphyton is abundant on macrophyte stems and on the 

decomposing vegetation substrate. 

In May 2002, vegetation in deep plots consisted of OBL 

floating and emergent vegetation including Nuphar advena, 

Nymphoides aquatica, Sagittaria latifolia, and Eleocharis 

equisetoides (table 8A). Chara sp. (musk grass), a species that 

typically is found in calcium carbonate-enriched waters, was 

abundant in deep plots. In the intermediate plots in May 2002, 

there was no standing water. The vegetation was a mix of OBL 

plants (Eleocharis equisetoides, Leersia hexandra, and Sagittaria latifolia), FACW plants (Amphicarpum muhlenbergianum 

and Hydrocotyle umbellata), and FAC plants (Andropogon 

virginicus and Phyla nodiflora). Transition plots were dry 

during May 2002 and FAC plants such as Phyla nodiflora were 

abundant.

 During the wet period, the plant community in deep 

plots was similar to that found in May 2002 (table 8B), although 

Eleocharis vivipara (OBL) also was abundant in May 2004. 

Table 7. Vegetation in fixed plots in W-03 Marsh.

[Shaded species make up 10 percent or more of the vegetation cover in a plot; >, greater than; --, not determined]

Depth below land-surface elevation at palmetto fringe1

Transitional plots

0-1.0 feet

Intermediate plots

1.0-2.0 feet

Deep plots

>2.0 feet

A. May 2002

Amphicarpum muhlenbergianum (FACW) Leersia hexandra (OBL) Nymphaea odorata (OBL)

Berchemia scandens (--) Panicum hemitomon (OBL) Panicum hemitomon (OBL)

Callicarpa americana (upland) Sagittaria latifolia (OBL) Sagittaria latifolia (OBL)

Myrica cerifera (FAC)

Pteridium aquilinum (--)

Rubus cuneifolius (FAC)

Serenoa repens (--)

B. October 2002, May 2003, October 2003, and May 2004

Amphicarpum muhlenbergianum (FACW) Berchemia scandens (--) Nymphaea odorata (OBL)

Andropogon glomeratus var. pumilus (--) Leersia hexandra (OBL) Panicum hemitomon (OBL)

Berchemia scandens (--) Ludwigia repens (OBL) Sagittaria latifolia (OBL)

Callicarpa americana (upland) Mikania scandens (--)

Leersia hexandra (OBL) Panicum hemitomon (OBL)

Myrica cerifera (FAC) Sagittaria latifolia (OBL)

Panicum hemitomon (OBL)

Pteridium aquilinum (--)

Quercus laurifolia (FACW)

Serenoa repens (--)

Smilax bona-nox (--)

172.44 feet NGVD of 1929.
28 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

Water depth in intermediate plots was much greater during the 

wet period (16-18 inches) than in May 2002, when intermediate 

plots were dry. Abundant vegetation included many of the same 

OBL species, with the addition of Fuirena squarrosa and 

Panicum hemitomon, but FAC species were not found. Transition plots were still dry during May 2004. Although there was 

no standing water in these plots, OBL plants such as Fuirena 

squarrosa, Ludwigia microcarpa, and Rhynchospora microcarpa, and the FACW species Panicum rigidulum were 

abundant.

Natural Cypress Wetlands

Green Swamp Cypress (fig. 3) is a natural wetland in 

which water levels fluctuate seasonally, sustaining healthy 

stands of Taxodium ascendens (OBL) and maintaining a welldeveloped palmetto fringe (Rochow and Lopez, 1984). Lyonia 

lucida (FACW) is widespread on cypress buttresses. GS Cypress 

is largely unaffected by human activities that can affect groundwater levels.

During May 2002, there was no standing water in 

GS Cypress. Taxodium ascendens (OBL) and Cephalanthus 

occidentalis (OBL) were the only plants present in deep plots in 

the wetland. Lyonia lucida (FACW) and Woodwardia virginica

(FACW) were present in intermediate plots. In the transition 

plots FAC (Lachnanthes caroliniana) and FACW (Woodwardia 

virginica and Lyonia lucida) species were abundant (table 9A). 

Although water depths were much greater during the wet 

period than during the dry period at GS Cypress (16-21 inches 

in deep plots; 8-10 inches in intermediate plots), the vegetation 

community remained virtually the same in these plots during 

both periods. The absence of nonwoody vegetation in deep and 

intermediate plots may be a result of the relatively high tree 

density in the wetland and the deep, darkly stained water in the 

wetland center, which may naturally inhibit growth of rooted 

aquatic plants. In transition plots, water depth was 1-3 inches.

Ludwigia lanceolata (OBL) was found in October 2003, in 

response to increased water levels occurring in the wet period 

(table 9B). 

Table 8. Vegetation in fixed plots in Duck Pond Marsh.

[Shaded species make up 10 percent or more of the vegetation cover in a plot; >, greater than; --, not determined]

Depth below land-surface elevation at hydric-soils indicator1

Transitional plots

0.0-2.0 feet

Intermediate plots

2.0-4.0 feet

Deep plots

>4.0 feet

A. May 2002

Andropogon virginicus (FAC) Amphicarpum muhlenbergianum (FACW) Chara sp. (--)

Erigeron quercifolius (FAC) Andropogon virginicus (FAC) Eleocharis equisetoides (OBL)

Phyla nodiflora (FAC) Centella asiatica (FACW) Nuphar aduena (OBL)

Rhynchospora microcarpa (OBL) Cyperus haspan (OBL) Nymphoides aquatica (OBL)

Eleocharis equisetoides (OBL) Sagittaria latifolia (OBL)

Hydrocotyle umbellata (FACW)

Leersia hexandra (OBL)

Mikania scandens (--)

Phyla nodiflora (FAC)

Sagittaria latifolia (OBL)

B. October 2002, May 2003, October 2003, and May 2004

Amphicarpum muhlenbergianum (FACW) Chara sp. (--) Chara sp. (--)

Andropogon glomeratus var. pumilus (--) Centella asiatica (FACW) Eleocharis equisetoides (OBL)

Andropogon virginicus (FAC) Cyperus haspan (OBL) Eleocharis vivipara (OBL)

Centella asiatica (FACW) Eleocharis equisetoides (OBL) Nuphar advena (OBL)

Erigeron quercifolius (FAC) Fuirena squarrosa (OBL) Nymphoides aquatica (OBL)

Fuirena squarrosa (OBL) Hydrocotyle umbellata (FACW) Sagittaria latifolia (OBL)

Hydrocotyle umbellata (FACW) Leersia hexandra (OBL)

Ludwigia microcarpa (OBL) Mikania scandens (--)

Panicum hemitomon (OBL) Panicum hemitomon (OBL)

Panicum rigidulum (FACW) Proserpinaca palustris (OBL)

Phyla nodiflora (FAC) Sagittaria latifolia (OBL)

Rhynchospora microcarpa (OBL)

170.48 feet above NGVD of 1929.
Relative Abundance of Wetland Plants in Fixed Plots 29

S-68 Cypress (fig. 7) is a natural wetland located in the 

Jay B. Starkey Wilderness Park. S-68 Cypress is in a part of the 

park far removed from production wells. It is unlikely that the 

wetland was affected by municipal ground-water withdrawals 

from the well field during 2002-2003, because of its remote 

location. In June 2000, there was evidence of soil subsidence 

(Berryman and Henigar, Inc., 2001), but this subsidence was 

most likely due to seasonal dry conditions rather than land-use 

activities. There is more herbaceous vegetation in S-68 Cypress 

compared to GS Cypress, perhaps because it has a more open 

tree canopy. 

In May 2002, all plots were dry at S-68 Cypress. The plant 

community in deep plots included Panicum hemitomon (OBL) 

and Rhynchospora corniculata (OBL). In intermediate plots, 

OBL (Hypericum fasiculatum) and FACW (Coelorachis rugosa), 

plants were abundant (table 10A). Andropogon virginicus (FAC)

was abundant in transition plots.

In the wet period, water levels throughout the wetland 

were much higher than during the dry period. In October 2003, 

the deep plots had 15-16 inches of water, and the OBL plants 

Panicum hemitomon and Utricularia purpurea were abundant 

(table 10B). Intermediate plots contained 7-8 inches of water; 

FACW (Coelorachis rugosa) and OBL plants (Panicum hemitomon and Utricularia purpurea) were abundant. Transition 

plots were saturated at land surface, but the plant community 

was similar to the May 2002 assessment.

Impaired Cypress Wetland

W-19 Cypress (fig. 10) is an impaired wetland affected by 

ground-water withdrawal and other activities in the Cypress 

Creek Well Field. Before ground-water withdrawal, W-19 

Cypress contained a healthy stand of Taxodium ascendens, as 

well as OBL (Cladium jamaicense and Pontederia cordata), and 

FACW species (Blechnum serrulatum, Woodwardia virginica, 

and Rhynchospora sp.) (Reynolds, Smith, & Hills, Inc., 2001). 

Well-field production began in 1976, and water levels in W-19 

Cypress have declined since that time. Water levels in the swamp 

fluctuate seasonally; however, water has been typically below 

land surface during many months of the year. There has been tree 

fall of Taxodium ascendens in the wetland. Machinery used to cut 

a firebreak through the wetland in 2002 grazed numerous trees and 

contributed to tree mortality. Acer rubrum (FACW) and Quercus 

laurifolia (FACW) are now found growing in the wetland.

All plots were dry in May 2002. In the deep plots, Paspalum 

repens (OBL) and Carex longii (FACW) were abundant (table 

11A). The intermediate and transition plots contained very little 

herbaceous vegetation. The wetland became inundated during 

the wet period beginning in October 2002. By October 2003, 

floating (Lemna obscura) and submersed (Utricularia foliosa, 

and U. inflata) OBL plants were abundant in the deep plots 

(table 11B), where water depth was 29-32 inches. These two 

species also were present in intermediate plots (water depth 10-17 

inches). In transition plots, Serenoa repens (overhanging, but not 

rooted in the plots) remained the only abundant species. 

Table 9. Vegetation in fixed plots in Green Swamp Cypress.

[Shaded species make up 10 percent or more of the vegetation cover in a plot; >, greater than; --, not determined]

Depth below land-surface elevation at palmetto fringe1

Transitional plots

0-1.0 feet

Intermediate plots

1.0-2.0 feet

Deep plots

>2.0 feet

A. May 2002

Lachnanthes caroliana (FAC) Lyonia lucida (FACW) Cephalanthus occidentalis (OBL)

Lyonia lucida (FACW) Woodwardia virginica (FACW) Taxodium ascendens (OBL)

Smilax laurifolia (--)

Toxicodendron radicans (--)

Vitis rotundifolia (--)

Woodwardia virginica (FACW)

B. October 2002, May 2003, October 2003, and May 2004

Lachnanthes caroliana (FAC) Ilex cassine (OBL) Cephalanthus occidentalis (OBL)

Ludwigia lanceolata (OBL) Lyonia lucida (FACW)

Lyonia lucida (FACW) Osmunda cinnamomea (FACW)

Sagittaria graminea (OBL) Woodwardia virginica (FACW)

Smilax laurifolia (--)

Vitis rotundifolia (--)

Woodwardia virginica (FACW)

Xyris fimbriata (OBL)

198.56 feet above NGVD of 1929.
30 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

Table 10. Vegetation in fixed plots in S-68 Cypress.

[Shaded species make up 10 percent or more of the vegetation cover in a plot; >, greater than; --, not determined]

Depth below land-surface elevation at palmetto fringe1

Transitional plots

0-1.0 feet

Intermediate plots

1.0-2.0 feet

Deep plots

>2.0 feet

A. May 2002

Amphicarpum muhlenbergianum (FACW) Aristida palustris (OBL) Panicum hemitomon (OBL)

Andropogon virginicus (FAC) Coelorachis rugosa (FACW) Rhynchospora corniculata (OBL)

Aristida stricta var. beyrichiana (FAC) Eupatorium capillifolium (FAC)

Dichanthelium ensifolium var. unciphyllum (FAC) Dichanthelium erectifolium (OBL)

Hypericum fasciculatum (OBL) Hypericum fasciculatum (OBL)

Hypericum myrtifolium (FACW) Panicum hemitomon (OBL)

Ilex glabra (--) Pluchea rosea (FACW)

Lachnanthes caroliana (FAC)

Serenoa repens (--)

B. October 2002, May 2003, October 2003, and May 2004

Amphicarpum muhlenbergianum (FACW) Aristida condensata (--) Panicum hemitomon (OBL)

Andropogon virginicus (FAC) Aristida palustris (OBL) Rhynchospora corniculata (OBL)

Andropogon virginicus var. glaucus (FAC) Coelorachis rugosa (FACW) Utricularia purpurea (OBL)

Aristida stricta var. beyrichiana (FAC) Hypericum fasciculatum (OBL)

Dichanthelium ensifolium var. unciphyllum (FAC) Panicum hemitomon (OBL)

Hypericum fasciculatum (OBL) Utricularia purpurea (OBL)

Hypericum myrtifolium (FACW)

Ilex glabra (--)

Lachnanthes caroliana (FAC)

Serenoa repens (--)

143.66 feet above NGVD of 1929.

Table 11. Vegetation in fixed plots in W-19 Cypress.

[Shaded species make up 10 percent or more of the vegetation cover in a plot; >, greater than; --, not determined]

Depth below land-surface elevation at palmetto fringe1

Transitional plots

0-1.0 feet

Intermediate plots

1.0-2.0 feet

Deep plots

>2.0 feet

A. May 2002

Melothria pendula (--) Acer rubrum (FACW) Carex longii (FACW)

Serenoa repens (--) Dichanthelium ensifolium var. unciphyllum 

(FAC)

Paspalum repens (OBL)

Toxicodendron radicans (--) Dichanthelium sp. (--) Ptilimnium capillaceum (FACW)

Myrica cerifera (FAC)

Toxicodendron radicans (--)

B. October 2002, May 2003, October 2003, and May 2004

Carex verrucosa (FACW) Lemna obscura (OBL) Carex longii (FACW)

Habenaria floribunda (FACW) Utricularia foliosa (OBL) Lemna obscura (OBL)

Mikania scandens (--) Utricularia inflata (OBL) Utricularia foliosa (OBL)

Serenoa repens (--) Utricularia inflata (OBL)

Toxicodendron radicans (--)

161.99 feet above NGVD of 1929.
Relative Abundance of Wetland Plants in Fixed Plots 31

Augmented Cypress Wetlands

S-63 Cypress (fig. 6) is a shallow, augmented wetland 

located in the Jay B. Starkey Wilderness Park. The wetland was 

dry for extended periods of time after well-field production 

began in 1974, and there was evidence of soil subsidence and 

compaction (Berryman and Henigar, 2001). Augmentation of 

the wetland began in 1990. Even with augmentation, the water 

level is below land surface for many months of the year. The 

canopy is dominated by Taxodium ascendens. This site had a 

greater diversity of plant species (greater than 35) than any of 

the other cypress sites in the study. Contributing factors could 

be the relatively low tree density, which allows greater light 

penetration to the wetland floor, and shallow but intermittent 

water levels, which facilitate germination and growth of many 

wetland plants.

During May 2002, deep plots had saturated soil, whereas 

transition and intermediate plots were dry. Dense vegetation in 

deep and intermediate plots included a mix of OBL, FACW, 

and FAC species. Abundant species included Aster elliotii 

(OBL), Lycopus rubellus (OBL), Rhynchospora corniculata 

(OBL), and Pluchea odorata (FACW) (table 12A). In the 

transition plots, abundant species included Andropogon virginicus 

(FAC) and Myrica cerifera (FAC).

During the wet period, water levels in the wetland varied, 

and declined quickly when the augmentation pump was not 

operating. Water depth in deep plots ranged from less than 1 to 

15 inches, and intermediate plots ranged from dry to a water 

depth of 9 inches. Aster elliottii (OBL) was found throughout 

the wetland and commonly filled 20-60 percent of deep and 

intermediate plots (table 12B). More OBL species were found 

in deep plots during October 2002 - May 2004 than during May 

2002, in response to deeper water. In contrast, vegetation did 

not differ greatly in intermediate plots between the May 2002 

dry period and the wet period. In transition plots, OBL species 

such as Rhynchospora microcarpa and R. miliacea were abundant during October 2002 - May 2004.

W-05 Cypress (fig. 9) is an augmented wetland located in 

the Cypress Creek Well Field. Before ground-water withdrawal, W-05 Cypress was a forested wetland dominated by 

Taxodium ascendens, and Eriocaulon sp. (pipeworts) were 

abundant in the wetland. W-05 Cypress has been augmented 

Table 12. Vegetation in fixed plots in S-63 Cypress.

[Shaded species make up 10 percent or more of the vegetation cover in a plot; >, greater than; --, not determined]

Depth of plots below land-surface elevation at palmetto fringe1

Transitional plots

0-0.5 feet

Intermediate plots

0.5-1.0 feet

Deep plots

>1.0 feet

A. May 2002

Amphicarpum muhlenbergianum (FACW) Acer rubrum (FACW) Blechnum serrulatum (FACW)

Andropogon virginicus (FAC) Aster elliottii (OBL) Cyperus distinctus (OBL)

Aristida stricta var. beyrichiana (FAC) Lycopus rubellus (OBL) Ludwigia repens (OBL)

Aster elliottii (OBL) Mikania scandens (--) Lycopus rubellus (OBL)

Blechnum serrulatum (FACW) Myrica cerifera (FAC) Mikania scandens (--)

Myrica cerifera (FAC) Panicum hemitomon (OBL) Pluchea odorata (FACW)

Rubus cuneifolius (FAC) Woodwardia virginica (FACW) Rhynchospora corniculata (OBL)

B. October 2002, May 2003, October 2003, and May 2004

Acer rubrum (FACW) Acer rubrum (FACW) Aster elliottii (OBL)

Amphicarpum muhlenbergianum (FACW) Aster elliottii (OBL) Blechnum serrulatum (FACW)

Andropogon virginicus (FAC) Coelorachis rugosa (FACW) Coelorachis rugosa (FACW)

Aristida stricta var. beyrichiana (FAC) Ludwigia repens (OBL) Cyperus distinctus (OBL)

Aster elliottii (OBL) Lycopus rubellus (OBL) Ludwigia repens (OBL)

Myrica cerifera (FAC) Mikania scandens (--) Mikania scandens (--)

Panicum hemitomon (OBL) Myrica cerifera (FAC) Myrica cerifera (FAC)

Panicum rigidulum (FACW) Panicum hemitomon (OBL) Panicum hemitomon (OBL)

Persea palustris (OBL) Rhynchospora miliacea (OBL) Rhynchospora corniculata (OBL)

Rhynchospora microcarpa (OBL) Saccharum baldwinii (OBL)

Rhynchospora miliacea (OBL) Woodwardia virginica (FACW)

Saccharum baldwinii (OBL)

Woodwardia virginica (FACW)

142.32 feet above NGVD of 1929.
32 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

since 1978. The water level typically is kept at 6-12 inches 

above land surface near the deepest point in the wetland, and 

the center of the wetland is not allowed to dry out seasonally. 

Following the onset of augmentation, Proserpinaca pectinata 

(OBL) and Riccia fluitans, which were previously absent, 

began to flourish (Ted Rochow, SWFWMD, written commun., 

2003). Growth of Riccia fluitans, a floating liverwort, was most 

likely due to changes in water quality (an increased concentration of calcium carbonate), and growth of Proserpinaca pectinata could have been spurred by increased water clarity in the 

wetland. Beginning in 1985, a buildup of unconsolidated 

bottom sediment (4-6 inches) was observed in the wetland 

(Ted Rochow, SWFWMD, written commun., 2003). This 

flocculent material may inhibit growth of some wetland 

species, including pipeworts, which have not been found in 

W-05 Cypress since 1985.

In May 2002, water depth was about 5 inches in deep plots 

and Riccia fluitans was the only plant present (table 13A). The 

ground was saturated in intermediate plots and the OBL species 

Rhynchospora corniculata was abundant. Transition plots were 

dry, and contained a mixture of FACW and FAC plants. By 

October 2003, deep plots had 14 inches of water, but Riccia 

fluitans was still the only nonwoody plant present. Intermediate 

plots had 3-7 inches of standing water during October 2002 - 

May 2004. Understory plants that were abundant in intermediate plots included several OBL species such as Rhynchospora 

corniculata, R. miliacea, and Sagittaria graminea (table 13B). 

Transition plots generally were saturated, but without standing 

water, and contained FAC or FACW species including Dichanthelium commutatum, Oplismenus hirtellus, Panicum anceps, 

and Panicum rigidulum (table 13B).

Relation of Wetland Vegetation to Bathymetry

Locating vegetation plots at distinctly different elevations 

along wetland transects was a useful design element in this 

study because it allowed vegetation assessment results to be 

directly related to wetland stage. Bathymetric data further 

extended the usefulness of stage and vegetation data because it 

allowed vegetation data to be related to inundated wetland area. 

For example, bathymetric data indicated that at GS Cypress 

when the wetland stage rose to the elevation of the intermediate 

plots, less than 30 percent of the wetland area was flooded 

(table 14), and about 70 percent of the wetland area at or above 

this elevation was dry. Recall that intermediate plots are located 

at a point along a transect line where the wetland elevation is 

approximately halfway between the deepest point in the wetland and the wetland perimeter. By comparison at GS Marsh, 

nearly 60 percent of the wetland area was inundated when water 

reached the intermediate plots, and about 40 percent of the wetland was dry. At the 10 wetlands in this study, the percentages 

of the wetland-surface areas that were flooded when stage 

Table 13. Vegetation in fixed plots in W-05 Cypress.

[Shaded species make up 10 percent or more of the vegetation cover in a plot; >, greater than; --, not determined]

Depth below land-surface elevation at palmetto fringe1

Transitional plots

0-0.5 feet

Intermediate plots

0.5-1.0 feet

Deep plots

>1.0 feet

A. May 2002

Callicarpa americana (upland) Lycopus rubellus (OBL) Riccia fluitans (--)

Dichanthelium commutatum (FAC) Rhynchospora corniculata (OBL)

Erechtites hieracifolia (FAC)

Melothria pendula (--)

Oplismenus hirtellus (FAC)

Panicum rigidulum (FACW)

Smilax bona-nox (--)

B. October 2002, May 2003, October 2003, and May 2004

Callicarpa americana (upland) Lycopus rubellus (OBL) Riccia fluitans (--)

Dichanthelium commutatum (FAC) Panicum rigidulum (FACW)

Melothria pendula (--) Polygonum hydropiperoides (OBL)

Oplismenus hirtellus (FAC) Rhynchospora corniculata (OBL)

Panicum anceps (FAC) Rhynchospora miliacea (OBL)

Panicum rigidulum (FACW) Sagittaria graminea (OBL)

Quercus laurifolia (FACW) Thelypteris palustris (--)

Smilax bona-nox (--)

171.47 feet above NGVD of 1929.
Relation of Wetland Vegetation to Bathymetry 33

reached the elevation of the intermediate plots ranged from 

about 12 percent at W-05 Cypress to about 66 percent at W-03 

Marsh (table 14). The volumes of water required to fill the individual wetlands to the elevation of their respective intermediate 

plots also varied greatly, from about 0.02 acre-ft at GS Cypress 

to 8.4 acre-ft at Duck Pond Marsh. Without bathymetric data, 

these water volumes would be difficult to predict.

The differences in wetland bathymetry have important 

implications with respect to both the impacts of declining water 

levels and the benefits of raising water levels with augmentation. Theoretically, if vegetation surveys indicate the encroachment of upland plants in intermediate plots at GS Cypress and 

GS Marsh, the proportional wetland areas affected by such 

encroachment would vary between 40 and 60 percent, depending on the shape of the wetland depression. Bathymetry data 

can provide context and a basis for interpretation of other elevation and vegetation data as well. For example, a cypress wetland is described as “significantly harmed” in the NTB area if 

the median water level over a long-term period is more than 

1.8 ft below normal pool elevation (Southwest Florida Water 

Management District, 2003a). Four of the five cypress wetlands 

mapped in this study would be dry if the water level was 1.8 ft 

below normal pool elevation. The fifth and deepest cypress 

wetland, W-19 (maximum depth 2.7 ft), would be flooded to 

about 18 percent of its total surface area if the water level was 

1.8 ft below normal pool elevation. 

Bathymetry data combined with routinely collected wetland stage data can be used to describe seasonal changes in the 

flooded area of impaired and natural wetlands (refer to fig. 16, 

W-29 Marsh and GS Marsh). One or more years of stage data 

can be used to describe a frequency distribution of the flooded 

area for a given wetland, which would indicate the amount of 

time different percentage areas of the wetland would be flooded 

during those years. The distribution of vegetation in wetlands is 

directly related to this inundation frequency, because wetland 

plants have adapted to survive and flourish under a somewhat 

predictable range of water depth. As a result, within a given 

period of time, the potential effects of human water-level alterations on wetland vegetation can be assessed by comparing and 

contrasting the flooded-area frequencies of an impaired wetland 

with that of a comparable natural wetland.

Inundated area was compared at an impaired wetland 

(W-29 Marsh) and a natural wetland (HRSP Marsh) during the 

same time period. W-29 Marsh is located on a municipal well 

field and for 15 years or more, its annual inundation period 

has been shortened by the effects of ground-water withdrawal 

(Reynolds, Smith and Hills, 2001). During the period July 17, 

2001 - July 16, 2002, the two production wells closest to W-29 

(both within 1,300 ft) yielded an annual average of 740.82 

million gallons (well CC-04) and 564.92 million gallons (well 

CC-05), for a combined total of 1,305.74 million gallons. 

During July 17, 2001 - July 16, 2002, W-29 Marsh had 20 percent or less of its surface area flooded about 80 percent of the 

period (fig. 18A), and for most of that time, the marsh was dry 

throughout. Only 21-60 percent of the total surface area of the 

wetland was inundated for the remaining 15 percent of the year 

(fig. 18A). In contrast, during the same period, HRSP Marsh, a 

natural wetland not affected by human activities including 

ground-water withdrawal, had more than 40 percent of its surface area inundated for about 75 percent of the time (fig. 18B). 

Rainfall amounts were comparable at the two wetlands during the 

period from July 17, 2001 - July 16, 2002: 51.59 inches at W-29 

Marsh and 52.15 inches at HRSP Marsh. Therefore, it is likely 

that well-field pumping was responsible for the low stages and 

Table 14. Elevation of vegetation plots and percent of wetland area inundated at specified elevations.

[Elevation is in feet above NGVD of 1929]

Wetland 

name

Wetland 

perimeter 

elevation

Transitional plots Intermediate plots Deep plots

Plot 

elevation

Position 

of plots 

below 

wetland 

perimeter

(feet)

Percent of 

wetland 

area 

inundated 

when 

plots 

are 

inundated

Plot 

elevation

Position 

of plots 

below 

wetland 

perimeter

(feet)

Percent of 

wetland 

area 

inundated 

when 

plots 

are 

inundated

Plot 

elevation

Position 

of plots 

below 

wetland 

perimeter

(feet)

Percent of 

wetland 

area 

inundated 

when 

plots 

are 

inundated

Duck Pond Marsh 70.48 70.18 0.30 93.1 68.48 2.00 59.3 66.65 3.83 36.4

Green Swamp Cypress 98.56 98.32 0.24 65.3 97.90 0.66 29.3 97.09 1.47 1.0

Green Swamp Marsh 93.30 93.06 0.24 82.8 92.64 0.66 57.7 92.53 0.77 44.5

Hillsborough River

State Park Marsh

46.35 45.80 0.55 51.1 45.60 0.75 40.0 45.13 1.22 23.5

S-63 Cypress 42.32 42.00 0.32 78.7 41.50 0.82 15.6 41.14 1.18 0.2

S-68 Cypress 43.66 43.43 0.23 84.9 42.78 0.88 51.2 42.23 1.43 0.4

W-03 Marsh 72.44 72.24 0.20 93.8 70.69 1.75 66.5 69.82 2.62 17.8

W-05 Cypress 71.47 70.87 0.60 44.8 70.62 0.85 12.2 70.04 1.43 1.6

W-19 Cypress 63.23 62.70 0.53 72.2 61.82 1.41 34.2 60.70 2.53 0.8

W-29 Marsh 69.92 69.30 0.62 80.3 68.22 1.70 48.8 67.12 2.80 0.1
34 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

(A) W-29 Marsh (B) HRSP Marsh

0-20% 21-40% 41-60% 61-80% >81%

0-20%

WET YEAR (July 17, 2002 to July 16, 2003)

21-40% 41-60% 61-80% >81%

0-20% 21-40% 41-60% 61-80% >81%

0-20% 21-40% 41-60% 61-80% >81%

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

DURATION OF INNUNDATION, IN PERCENT OF YEAR

AVERAGE YEAR (July 17, 2001 to July 16, 2002)

INUNDATED AREA, AS A PERCENT OF TOTAL WETLAND AREA

(C) W-29 Marsh (D) HRSP Marsh

IMPAIRED NATURAL

small wetted areas observed at W-29 Marsh compared with 

HRSP Marsh during this average rainfall year (Southwest 

Florida Water Management District, 2003b). 

In the following year (July 17, 2002 - July 16, 2003), 

which was wetter than the previous period, both W-29 Marsh 

and HRSP Marsh had more than 60 percent of their wetlandsurface areas inundated for about 60-65 percent of the year (fig. 

18C,D). The similarity in flooded area between the natural wetland and the impaired wetland during this second year reflected 

the substantially reduced quantities of ground-water withdrawals in the vicinity of W-29 Marsh, and the increased rainfall at 

W-29 Marsh compared with HRSP Marsh. In fact, production 

at well CC-04 decreased by 40 percent and production at well 

CC-05 decreased by 14 percent (Tampa Bay Water, 2003). 

Moreover, W-29 Marsh received almost 53 percent more rainfall and HRSP Marsh received about 25 percent more rainfall 

during July 2002 - July 2003 than during the previous year. As 

a result of the reduced pumping and increased rainfall, Upper 

Floridan aquifer water levels beneath W-29 Marsh averaged 

about 14 ft higher during July 2002 - July 2003 than during the 

previous year. 

Histograms were developed for W-29 Marsh and HRSP 

Marsh for these 2 consecutive years to show the frequency of 

inundation at the elevations of the transition, intermediate, and 

deep vegetation plots. The contrast between the natural site and 

the impaired site was again greatest during the average year 

(July 17, 2001- July 16, 2002) (fig. 19A,B). Deep plots at W-29 

Marsh were inundated only 30 percent of the time (fig. 19A). 

A late-summer 2001 inundation may have been sufficient to 

support the one OBL species that grew in deep plots in May 

2002. Intermediate plots were inundated less than 10 percent of 

the time during July 2001- July 2002, and standing water was 

never present in the transition plots at W-29 Marsh. The long 

periods of dry conditions in deep and intermediate plots at this 

impaired site may have prevented the growth of other OBL 

species and inhibited the growth of FACW species as well. 

Deep plots at HRSP Marsh, however, were inundated about 

80 percent of the year during July 2001- July 2002 (fig. 19B). 

Intermediate plots were inundated for more than 70 percent of 

the time, and the transition plots had water at the surface more 

than 40 percent of the time. Long periods of inundation 

enhanced the survival of OBL and FACW species in deep and 

intermediate plots at this natural site. 

Figure 18. Inundated area at an impaired marsh and a natural marsh during an average year and a wet year.
Summary and Conclusions 35

(A) W-29 Marsh (B) HRSP Marsh

Transition plots

WET YEAR (July 17, 2002 to July 16, 2003)

Intermediate plots Deep plots

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

100

80

60

40

20

0

DURATION OF INNUNDATION, IN PERCENT OF YEAR

AVERAGE YEAR (July 17, 2001 to July 16, 2002)

(C) W-29 Marsh (D) HRSP Marsh

IMPAIRED NATURAL

Transition plots Intermediate plots Deep plots

Transition plots Intermediate plots Deep plots Transition plots Intermediate plots Deep plots

The following year (July 17, 2002 - July 16, 2003), the 

flooded area histograms for these two marshes indicate similar 

periods of inundation at the vegetation plots (fig. 19C,D). Intermediate and deep plots were inundated 90-100 percent of the 

year in both wetlands. The greatest difference occurred at the 

elevation of the transition plots. At W-29 Marsh, the transition 

plots were inundated for about 50 percent of the year (fig. 19C), 

whereas at HRSP Marsh transition plots had water at the surface almost 90 percent of the year (fig. 19D).

Vegetative surveys alone can be an ambiguous indicator of 

the frequency of flooding in different areas of some wetlands. 

Many herbaceous species display variable tolerances for flooding and desiccation; in this study, several species were observed 

across a gradient of elevation in both the impaired and natural 

wetlands. For example, at Green Swamp Marsh, the OBL grass 

Panicum hemitomon was present in deep and intermediate plots 

in May 2002 when the ground was saturated, with no standing 

water. The species was again found at this site in deep and intermediate plots in October 2003 when water depths were 10-15 

inches. P. hemitomon was present (albeit at a lower density and 

with numerous plants apparently dead) in deep and intermediate 

plots at W-29 Marsh in May 2002 when those plots were dry. 

At W-29 Marsh in October 2003, P. hemitomon was found in all 

three plots where water depth ranged from 8-36 inches. 

 Spatial and temporal patterns of inundation sustained over 

a period of years determines the distribution of long-lived wetland vegetation, including trees and shrubs, and allows the longterm maintenance of viable habitat for wetland wildlife. Constructing flooded-area frequencies for natural wetlands based 

on long-term stage record would provide a more representative 

indication of long-term average conditions compared to sporadic vegetation assessments with little or no associated stage 

data. The utility and robustness of estimates of long-term average conditions would be enhanced if a large number of natural 

wetlands representing a range of hydrologic conditions could be 

included.

Summary and Conclusions

A careful determination of the wetland perimeter is essential for reliable stage-area and stage-volume estimates. At 9 of 

the 10 wetland sites in this study, the palmetto fringe was used 

to delineate the perimeter of the wetland and the elevation that 

corresponded to 100 percent inundation. The palmetto fringe 

was shown in separate work done by the SWFWMD to be a 

dependable indicator of a wetland boundary in the NTB area, 

both because of its low tolerance for flooding and because of 

the close correlation between the elevation of this plant and the 

Figure 19. Duration of inundation of vegetation plots at an impaired marsh and a natural marsh during an average year and 

a wet year. 
36 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

elevation of vegetative normal pool indicators in the interior of 

Florida wetlands. Hydric-soils indicators, which are considerably more labor-intensive to determine, were used to delineate 

the wetland perimeter at Duck Pond Marsh because no palmetto fringe or other vegetative normal pool indicators were 

present. 

More than one approach was needed to collect bathymetric 

data in this study because the wetlands differ in their depth, 

size, extent of inundation, and density of vegetation. Choosing 

the appropriate density of data points needed to determine wetland bathymetry depends on the intended use of the data and the 

physical characteristics of the site. For example, a bathymetric 

map based upon fewer data points may be adequate for describing the fraction of total wetland area flooded in 20-percent 

intervals. In contrast wetland water budgets, which are used to 

estimate the volume of ground water flowing through a wetland, are very sensitive to uncertainties in stage-area and stagevolume relations, and therefore, require the greatest density of 

bathymetric data points possible.

For small, shallow wetlands such as those found throughout 

the NTB area, the most detailed bathymetric data collected 

were data sets collected using the Topcon method. This method 

requires a clear line of sight and it maps elevation data points 

across the entire wetland bottom at frequent and regular spatial 

intervals. This method was used whenever possible in this 

study. Simpler approaches were used when necessary to 

accommodate physical characteristics of the study wetlands. 

The collection of bathymetric data along two or three transect 

lines across a wetland was the simplest method tested in this 

study. The transect method generated values of wetland area 

and volume at intermediate wetland stages that were 50-100 

percent lower than the approach that used a high density of 

data points. An alternative simple approach, which added data 

points along a single water-level contour to the transect data set, 

generated area and volume estimates that agreed much more 

closely with the approach using a high density of data points. In 

wetlands such as those in this study, the bathymetric data points 

along a contour line could be collected readily by using a DGPS 

unit to map the water’s edge when the wetland is less than 100 

percent inundated. Errors associated with estimates of wetland 

area and water volume in both of the simpler approaches were 

lowest when stage approached the elevation of the wetland 

perimeter. All three methods were subject to additional bathymetry measurement errors attributable to the vegetative cover 

and the rough surface of the wetland landscape. 

Bathymetric data greatly extended the physical importance 

of stage data collected at a single point in a wetland, particularly 

if the point was in the deepest area of the wetland. Stage-area 

curves created from bathymetric data show that in all 10 wetlands, the flooded area changes markedly, and non-linearly, 

with wetland stage. The wetland perimeter indicates the flooded 

area at highest stage, but at stages below 100 percent full, 

bathymetric data are essential to predict flooded area. Further, 

it is the extent of flooded surface area, and not water level at the 

staff gage, that determines whether a wetland will be “wet” or 

“dry.” When no bathymetric data are available, it is difficult to 

estimate flooded area from stage data. With bathymetry, stage 

data could be translated into spatial data on flooded area, which 

could then be tracked over time. Staff gages located at the lowest topographic position in a wetland were advantageous 

because they provided flooded-area information over the most 

complete range of stage and time. 

Placing vegetation plots at distinct and predetermined 

elevations along a transect allowed wetland vegetation to be 

related to flooded area. A knowledge of the location and elevation of the plots can create the basis for extrapolating the composition of the vegetation community in those plots to areas of 

similar elevation throughout the entire wetland. Wetland 

bathymetry results expanded wetland vegetation community 

assessment into the landscape scale. The results allowed waterlevel alterations to be interpreted in terms of wetland area, and 

loss (or gain) of habitat. Vegetation assessments in wetlands 

were enhanced as a quantitative management tool when coupled 

with data on the elevation of vegetation plots and the location of 

transects and by combining vegetation results with information 

on wetland bathymetry.

Bathymetric data can be used to provide useful insights to 

water managers who may need to augment water levels of multiple impaired wetlands as well as optimize the use of a finite 

allocation of augmentation water. Bathymetric contours derived 

for the 10 wetland sites in this study indicated that at lower 

stages a relatively small volume of water, and sometimes a 

small incremental rise in stage, often increased the flooded wetland area by a large amount. When the stage approached the elevation of the palmetto fringe, a large volume of water was 

required to increase the surface area by a small amount. With 

improved information on wetland stage, area, and volume, 

water managers could recommend target stages in order to flood 

predetermined wetland-surface areas with a certain frequency. 

Ideally, wetland mitigation using augmentation would 

attempt to approximate natural wetland flooding cycles. This 

would entail not only timing the presence or absence of water at 

the deepest point in the wetland, but also restoring the natural 

frequency of flooding across a range of wetland elevations. 

Bathymetric and long-term stage data can be used to characterize the flooded-area frequencies in natural wetlands for a given 

year, for different climatic cycles, and for longer historical periods. Comparing the flooded-area frequencies of natural wetlands to augmented wetlands provides a quantitative guidepost 

for evaluating the success of mitigation efforts in augmented 

wetlands from a spatial perspective. Flooded-area frequencies 

of impaired wetlands can be analyzed to determine the extent of 

hydrologic change spatially, and to select the best candidate 

wetlands for augmentation. Dominant plant species associated 

with different flooded-area frequencies in natural wetlands 

could provide a parallel goal for restoring vegetation in augmented wetlands, given similar bathymetry and rainfall. A drop 

in stage caused by human activities at an impaired wetland 

could be related to a decrease in flooded area, an altered vegetation community at specified elevations, and an associated 
References 37

change in wetland wildlife habitat. If these changes could 

be compared with contemporary natural wetlands, a semiquantitative assessment of impact could be derived even in 

the absence of long-term stage data or long-term monitoring.

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Marsh, Manitoba: Canadian Journal of Botany, v. 70, 

p. 1860-1867.

Tampa Bay Water, 2000, Environmental management plan for 

the Tampa Bay Water central system wellfields, March 4, 

2000: Clearwater, 58 p.

Tampa Bay Water, 2003, Optimized regional operations plan 

annual report for water year 2003: Prepared for Southwest 

Florida Water Management District: Clearwater, 36 p. 

U.S. Fish and Wildlife Service, 2004, National Wetlands 

Inventory (NWI) Metadata: Accessed June 1, 2004, at 

http://wetlands.fws.gov/other/metadata/nwi_meta.txt.

van der Valk, A.G., and Welling, C.H., 1988, The development 

of zonation in freshwater wetlands: An experimental 

approach, in During, H.J., Werger, M.J., and Willems, J.H., 

Diversity and pattern in plant communities: The Hague, 

Netherlands, S.P.B. Academic Publishing.

Ward, G.M., 1998, A preliminary analysis of hydrodynamic 

characteristics of a small lotic wetland ecosystem: Verhein 

International Verein, Limnologie, v. 26, p. 1373-1376.

White, W.A., 1970. The geomorphology of the Florida Peninsula: Tallahassee, Bureau of Geology Bulletin 5, 164 p.

Winter, T.C., 1988, A conceptual framework for assessing 

cumulative impacts on the hydrology of non-tidal wetlands: 

Environmental Management, v. 12, no. 5, p. 605-620.

Winter, T.C., and LaBaugh, J.W., 2003, Hydrologic considerations in defining isolated wetlands: Wetlands , v. 23, no. 3, 

p. 532-540.

Wise, W.R., Annable, M.D., Walser, J.A.E., Swift, R.S., Shaw, 

D.T., 2000, A wetland-aquifer interaction test: Journal of 

Hydrology, v. 227, p. 257-272.

Wunderlin, R.P., 1998, Guide to the vascular plants of Florida: 

Gainesville, University Press of Florida, 809 p.

Wunderlin, R.P., and Hansen, B.F., 2004, Atlas of Florida 

Vascular Plants: Tampa, Institute for Systematic Botany, 

University of South Florida, Accessed June 28, 2004 at 

http://www.plantatlas.usf.edu.
 39

Appendixes 1-13
Appendix 1. Comprehensive list of wetland staff gages and offsets to NGVD of 1929.

[SWFWMD, Southwest Florida Water Management District; N, north; W, west; latitude and longitude in degrees (o), 

minutes (′), and seconds (′′). 

Staff gage designation

Reading at top

of designated 

staff gage1

(feet)

Staff gage location Staff gage 

offset 

Latitude Longitude (feet)

Duck Pond Marsh shallow 10.04 28o21′59.04′′N 82o28′01.92′′W 63.82

Duck Pond Marsh SWFWMD 71.30 28o21′59.04′′N 82o28′01.92′′W -0.08

Duck Pond Marsh deep 6.66 28o21′58.68′′N 82o28′02.64′′W 63.83

Green Swamp Cypress 2.00 28o24′46.80′′N 81o57′39.60′′W 0.02

Green Swamp Marsh 98.54 28o21′15.48′′N 82o01′02.28′′W -0.15

Hillsborough River

State Park Marsh

50.94 28o08′49.20′′N 82o13′40.80′′W 0.27

S-63 Cypress 3.33 28o14′55.32′′N 82o35′00.24′′W 40.41

S-68 Cypress 47.53 28o14′18.24′′N 82o34′29.64′′W -0.06

W-03 Marsh 1 3.33 28o18′12.60′′N 82o22′40.08′′W 69.33

W-03 Marsh SWFWMD 74.74 28o18′12.60′′N 82o22′39.72′′W -2.02

W-03 Marsh 3 3.33 28o18′12.60′′N 82o22′39.72′′W 69.32

W-05 Cypress 9.99 28o18′18.36′′N 82o22′55.20′′W 63.30

W-19 Cypress 6.65 28o16′42.24′′N 82o23′51.72′′W 60.14

W-29 Marsh B1 9.99 28o17′58.20′′N 82o23′16.80′′W 64.11

W-29 Marsh B2 USGS 3.34 28o17′53.88′′N 82o23′12.84′′W 67.20

1Reading at top of staff gage was used to distinguish between multiple unmarked or poorly marked staff gages at a 

single wetland.

40 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004
Appendix 2. Estimated area and volume of water corresponding to 

stage and depth below land surface elevation at palmetto fringe in 

Duck Pond Marsh.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 70.48 5.19 16.61

0.1 70.38 5.08 16.10

0.2 70.28 4.97 15.60

0.3 70.18 4.86 15.11

0.4 70.08 4.75 14.63

0.5 69.98 4.64 14.16

0.6 69.88 4.54 13.70

0.7 69.78 4.44 13.25

0.8 69.68 4.33 12.81

0.9 69.58 4.23 12.38

1.0 69.48 4.13 11.96

1.1 69.38 4.02 11.56

1.2 69.28 3.91 11.16

1.3 69.18 3.81 10.77

1.4 69.08 3.70 10.40

1.5 68.98 3.59 10.03

1.6 68.88 3.48 9.68

1.7 68.78 3.38 9.34

1.8 68.68 3.28 9.00

1.9 68.58 3.18 8.68

2.0 68.48 3.08 8.37

2.1 68.38 2.98 8.06

2.2 68.28 2.90 7.77

2.3 68.18 2.81 7.48

2.4 68.08 2.73 7.21

2.5 67.98 2.66 6.94

2.6 67.88 2.59 6.68

2.7 67.78 2.52 6.42

2.8 67.68 2.45 6.17

2.9 67.58 2.39 5.93

3.0 67.48 2.31 5.69

3.5 66.98 2.05 4.60

4.0 66.48 1.79 3.64

4.5 65.98 1.56 2.81

5.0 65.48 1.37 2.07

5.5 64.98 1.18 1.44

6.0 64.48 0.98 0.90

6.5 63.98 0.75 0.47

7.0 63.48 0.43 0.16

7.5 62.98 0.15 0.025

8.0 62.48 0.003 0.000

Appendixes 41

Appendix 3. Estimated area and volume of water corresponding 

to stage and depth below land surface elevation at palmetto 

fringe in Green Swamp Cypress.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 98.56 1.67 0.81

0.1 98.46 1.49 0.65

0.2 98.36 1.19 0.52

0.3 98.26 0.94 0.41

0.4 98.16 0.76 0.33

0.5 98.06 0.64 0.26

0.6 97.96 0.55 0.20

0.7 97.86 0.45 0.15

0.8 97.76 0.37 0.10

0.9 97.66 0.30 0.071

1.0 97.56 0.23 0.045

1.1 97.46 0.16 0.025

1.2 97.36 0.085 0.013

1.3 97.26 0.050 0.007

1.4 97.16 0.029 0.003

1.5 97.06 0.012 0.001

1.6 96.96 0.002 0.000
Appendix 4. Estimated area and volume of water corresponding to 

stage and depth below land surface elevation at palmetto fringe in 

Green Swamp Marsh.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 93.30 1.63 1.01

0.1 93.20 1.49 0.85

0.2 93.10 1.39 0.71

0.3 93.00 1.29 0.58

0.4 92.90 1.19 0.45

0.5 92.80 1.10 0.34

0.6 92.70 1.00 0.23

0.7 92.60 0.90 0.14

0.8 92.50 0.65 0.059

0.9 92.40 0.25 0.012

1.0 92.30 0.029 0.001

1.1 92.20 0.000 0.000

42 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

Appendix 5. Estimated area and volume of water corresponding to 

stage and depth below land surface elevation at palmetto fringe in 

Hillsborough River State Park Marsh.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 46.35 2.21 1.48

0.1 46.25 1.82 1.28

0.2 46.15 1.55 1.11

0.3 46.05 1.41 0.96

0.4 45.95 1.30 0.83

0.5 45.85 1.19 0.70

0.6 45.75 1.07 0.59

0.7 45.65 0.93 0.49

0.8 45.55 0.84 0.40

0.9 45.45 0.76 0.32

1.0 45.35 0.69 0.25

1.1 45.25 0.62 0.18

1.2 45.15 0.54 0.12

1.3 45.05 0.44 0.075

1.4 44.95 0.31 0.037

1.5 44.85 0.13 0.015

1.6 44.75 0.043 0.008

1.7 44.65 0.025 0.004

1.8 44.55 0.015 0.002

1.9 44.45 0.009 0.001

2.0 44.35 0.005 0.001

2.1 44.25 0.002 0.000
Appendix 6. Estimated area and volume of water corresponding to 

stage and depth below land surface elevation at palmetto fringe in 

S-63 Cypress.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 42.32 1.26 0.73

0.1 42.22 1.19 0.60

0.2 42.12 1.10 0.49

0.3 42.02 1.01 0.38

0.4 41.92 0.92 0.29

0.5 41.82 0.83 0.20

0.6 41.72 0.72 0.12

0.7 41.62 0.52 0.057

0.8 41.52 0.23 0.018

0.9 41.42 0.066 0.005

1.0 41.32 0.016 0.002

1.1 41.22 0.006 0.001

1.2 41.12 0.002 0.000

1.3 41.02 0.000 0.000

Appendixes 43

Appendix 7. Estimated area and volume of water corresponding to 

stage and depth below land surface elevation at palmetto fringe in 

S-68 Cypress.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 43.66 5.79 4.57

0.1 43.56 5.48 4.00

0.2 43.46 5.03 3.48

0.3 43.36 4.65 3.00

0.4 43.26 4.33 2.55

0.5 43.16 4.05 2.13

0.6 43.06 3.78 1.74

0.7 42.96 3.51 1.37

0.8 42.86 3.21 1.04

0.9 42.76 2.90 0.73

1.0 42.66 2.52 0.46

1.1 42.56 2.04 0.23

1.2 42.46 1.05 0.069

1.3 42.36 0.25 0.012

1.4 42.26 0.030 0.001

1.5 42.16 0.000 0.000
Appendix 8. Estimated area and volume of water corresponding to 

stage and depth below land surface elevation at palmetto fringe in 

W-03 Marsh.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 72.44 7.38 13.95

0.1 72.34 7.15 13.23

0.2 72.24 6.92 12.52

0.3 72.14 6.73 11.84

0.4 72.04 6.56 11.18

0.5 71.94 6.41 10.53

0.6 71.84 6.27 9.90

0.7 71.74 6.14 9.28

0.8 71.64 6.02 8.67

0.9 71.54 5.91 8.07

1.0 71.44 5.79 7.49

1.1 71.34 5.68 6.91

1.2 71.24 5.57 6.35

1.3 71.14 5.46 5.80

1.4 71.04 5.35 5.26

1.5 70.94 5.23 4.73

1.6 70.84 5.11 4.21

1.7 70.74 4.98 3.71

1.8 70.64 4.84 3.22

1.9 70.54 4.69 2.74

2.0 70.44 4.53 2.28

2.1 70.34 4.35 1.83

2.2 70.24 4.11 1.41

2.3 70.14 3.73 1.02

2.4 70.04 2.92 0.68

2.5 69.94 2.02 0.36

2.6 69.84 1.43 0.26

2.7 69.74 0.84 0.15

2.8 69.64 0.21 0.10

2.9 69.54 0.090 0.085

3.0 69.44 0.064 0.078

3.5 68.94 0.046 0.050

4.0 68.44 0.035 0.030

4.5 67.94 0.025 0.015

5.0 67.44 0.016 0.005

44 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

Appendix 9. Estimated area and volume of water corresponding to 

stage and depth below land surface elevation at palmetto fringe in 

W-05 Cypress.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 71.47 8.78 4.58

0.1 71.37 8.13 3.74

0.2 71.27 6.86 2.99

0.3 71.17 6.05 2.35

0.4 71.07 5.40 1.77

0.5 70.97 4.73 1.27

0.6 70.87 3.93 0.83

0.7 70.77 2.49 0.51

0.8 70.67 1.36 0.32

0.9 70.57 0.78 0.21

1.0 70.47 0.55 0.15

1.1 70.37 0.39 0.10

1.2 70.27 0.30 0.068

1.3 70.17 0.23 0.041

1.4 70.07 0.16 0.022

1.5 69.97 0.093 0.009

1.6 69.87 0.031 0.003

1.7 69.77 0.015 0.001

1.8 69.67 0.006 0.000

1.9 69.57 0.000 0.000
Appendix 10. Estimated area and volume of water corresponding 

to stage and depth below land surface elevation at palmetto fringe 

in W-19 Cypress.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 63.23 2.08 2.26

0.1 63.13 1.96 2.06

0.2 63.03 1.83 1.87

0.3 62.93 1.72 1.69

0.4 62.83 1.62 1.53

0.5 62.73 1.53 1.37

0.6 62.63 1.44 1.22

0.7 62.53 1.36 1.08

0.8 62.43 1.28 0.95

0.9 62.33 1.19 0.82

1.0 62.23 1.10 0.71

1.1 62.13 1.01 0.60

1.2 62.03 0.91 0.51

1.3 61.93 0.82 0.42

1.4 61.83 0.72 0.34

1.5 61.73 0.63 0.28

1.6 61.63 0.54 0.22

1.7 61.53 0.47 0.17

1.8 61.43 0.38 0.12

1.9 61.33 0.32 0.089

2.0 61.23 0.26 0.060

2.1 61.13 0.19 0.038

2.2 61.03 0.13 0.022

2.3 60.93 0.082 0.011

2.4 60.83 0.051 0.005

2.5 60.73 0.022 0.001

2.6 60.63 0.004 0.000

2.7 60.53 0.000 0.000

Appendixes 45

Appendix 11. Estimated area and volume of water corresponding 

to stage and depth below land surface elevation at palmetto fringe 

in W-29 Marsh.

[Stage, elevation in feet above NGVD of 1929. Area and volume values derived 

using SURFER]

Depth

(feet) Stage Area(acres)

Volume

(acre-feet)

0 69.92 6.52 9.42

0.1 69.82 6.30 8.78

0.2 69.72 6.07 8.16

0.3 69.62 5.85 7.57

0.4 69.52 5.64 6.99

0.5 69.42 5.45 6.44

0.6 69.32 5.27 5.90

0.7 69.22 5.09 5.38

0.8 69.12 4.91 4.88

0.9 69.02 4.73 4.40

1.0 68.92 4.55 3.94

1.1 68.82 4.37 3.49

1.2 68.72 4.19 3.07

1.3 68.62 4.01 2.66

1.4 68.52 3.81 2.26

1.5 68.42 3.60 1.89

1.6 68.32 3.37 1.54

1.7 68.22 3.18 1.22

1.8 68.12 2.80 0.92

1.9 68.02 2.41 0.66

2.0 67.92 1.82 0.45

2.1 67.82 1.21 0.30

2.2 67.72 0.79 0.20

2.3 67.62 0.59 0.13

2.4 67.52 0.43 0.083

2.5 67.42 0.31 0.046

2.6 67.32 0.20 0.020

2.7 67.22 0.10 0.005

2.8 67.12 0.000 0.000
46 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

Appendix 12. Names and status of wetland plants identified in fixed plots at wetland sites.

[sp., species; --, not determined; FACW, facultative wet; FAC, facultative; OBL, obligate]

Scientific name Common name Status1,2

Acer rubrum Red maple FACW

Amphicarpum muhlenbergianum Blue maidencane FACW

Andropogon glomeratus var. pumilus Bushy bluestem --

Andropogon virginicus Broomsedge bluestem FAC

Andropogon virginicus var. glaucus Chalky bluestem FAC

Aristida condensata Big threeawn --

Aristida palustris Longleaf threeawn OBL

Aristida stricta var. beyrichiana Wiregrass FAC

Aster elliottii Elliott's aster OBL

Berchemia scandens Rattan vine --

Blechnum serrulatum Swamp fern FACW

Boehmeria cylindrica Bog hemp OBL

Callicarpa americana American beautyberry upland

Carex joorii Cypress swamp sedge FACW

Carex longii Long’s sedge FACW

Carex verrucosa Warty sedge FACW

Celtis laevigata Sugarberry FACW

Centella asiatica Asiatic pennywort FACW

Cephalanthus occidentalis Common buttonbush OBL

Chara sp. Musk-grass --

Cladium jamaicense Jamaica swamp sawgrass OBL

Coelorachis rugosa Wrinkled jointtailgrass FACW

Conyza canadensis Canadian horseweed upland

Cyperus distinctus Swamp flatsedge OBL

Cyperus haspan Haspan flatsedge OBL

Cyperus polystachyos Manyspike flatsedge FACW

Dichanthelium commutatum Variable witchgrass FAC

Dichanthelium ensifolium var. unciphyllum Cypress witchgrass FAC

Dichanthelium erectifolium Erectleaf witchgrass OBL

Dichanthelium sp. Witchgrass --

Eleocharis baldwinii Baldwin’s spikerush OBL

Eleocharis elongata Slim spikerush OBL

Eleocharis equisetoides Jointed spikerush OBL

Eleocharis vivipara Viviparous spikerush OBL

Eragrostis spectabilis Purple lovegrass FAC

Erechtites hieraciifolius Fireweed FAC

Erigeron quercifolius Oakleaf fleabane FAC

Eriocaulon compressum Flattened pipewort OBL

Eupatorium capillifolium Dogfennel FAC

Eupatorium leptophyllum Falsefennel OBL

Euthamia caroliniana Slender flattop goldenrod FAC

Fimbristylis autumnalis Slender fimbry OBL

Fuirena squarrosa Hairy umbrellasedge OBL

Galium tinctorium Stiff marsh bedstraw FACW

Habeneria floribunda Mignonette orchid FACW

Hydrocotyle umbellata Manyflower marshpennywort FACW

Hypericum fasciculatum Peelbark St. Johns-wort OBL

Hypericum myrtifolium Myrtleleaf St. Johns-wort FACW
Appendixes 47

Ilex cassine Dahoon holly OBL

Ilex glabra Gallberry --

Juncus marginatus Shore rush FACW

Lachnanthes caroliana Carolina redroot FAC

Leersia hexandra Southern cutgrass OBL

Lemna obscura Little duckweed OBL

Ludwigia lanceolata Lanceleaf primrosewillow OBL

Ludwigia linearis Narrowleaf primrosewillow OBL

Ludwigia microcarpa Smallfruit primrosewillow OBL

Ludwigia octovalis Mexican primrosewillow OBL

Ludwigia repens Creeping primrosewillow OBL

Lycopus rubellus Taperleaf waterhorehound OBL

Lyonia lucida Fetterbush FACW

Melothria pendula Creeping cucumber --

Mikania scandens Climbing hempvine --

Myrica cerifera Wax myrtle FAC

Nuphar advena Yellow pondlily OBL

Nymphaea odorata American white waterlily OBL

Nymphoides aquatica Big floatingheart OBL

Oldenlandia uniflora Clustered mille graines FACW

Oplismenus hirtellus Basketgrass FAC

Osmunda cinnamomea Cinnamon fern FACW

Oxypolis filiformis Water dropwort OBL

Paederia foetida Skunkvine --

Panicum anceps Beaked panicum FAC

Panicum hemitomon Maidencane OBL

Panicum rigidulum Redtop panicum FACW

Panicum verrucosum Warty panicgrass FACW

Panicum virgatum Switchgrass FACW

Paspalum laeve Field paspalum FACW

Paspalum repens Water paspalum OBL

Paspalum sp. Paspalum --

Persea palustris Swamp bay OBL

Phyla nodiflora Turkey tangle fogfruit FAC

Pinus elliottii Slash pine --

Pluchea odorata Sweetscent FACW

Pluchea rosea Rosy camphorweed FACW

Polygala lutea Orange milkwort FACW

Polygonum hydropiperoides Swamp smartweed OBL

Pontederia cordata Pickerelweed OBL

Proserpinaca palustris Marsh mermaidweed OBL

Proserpinaca pectinata Combleaf mermaidweed OBL

Pteridium aquilinum Bracken fern --

Ptilimnium capillaceum Mock bishopsweed FACW

Quercus laurifolia Laurel oak FACW

Quercus nigra Water oak FACW

Quercus sp. Oak --

Appendix 12. Names and status of wetland plants identified in fixed plots at wetland sites. (Continued)

[sp., species; --, not determined; FACW, facultative wet; FAC, facultative; OBL, obligate]

Scientific name Common name Status1,2
48 Bathymetry and Vegetation in Isolated Marsh and Cypress Wetlands in the Northern Tampa Bay Area, 2000-2004

Rhexia sp. Meadowbeauty FACW

Rhynchospora cephalantha Bunched beaksedge OBL

Rhynchospora corniculata Shortbristle horned beaksedge OBL

Rhynchospora fascicularis Fascicled beaksedge FACW

Rhynchospora inundata Narrowfruit horned beaksedge OBL

Rhynchospora microcarpa Southern beaksedge OBL

Rhynchospora miliacea Millet beaksedge OBL

Riccia fluitans Floating liverworts --

Rubus cuneifolius Sand blackberry FAC

Saccharum baldwinii Narrow plumegrass OBL

Saccharum giganteum Sugarcane plumegrass OBL

Sacciolepis striata American cupscale OBL

Sagittaria graminea Grassy arrowhead OBL

Sagittaria latifolia Common arrowhead OBL

Salix caroliniana Carolina willow OBL

Scleria baldwinii Baldwin's nutrush FACW

Scleria cililata Fringed nutrush FACW

Serenoa repens Saw palmetto --

Smilax bona-nox Saw greenbrier --

Smilax laurifolia Laurel greenbrier --

Taxodium ascendens Pond-cypress OBL

Thelypteris palustris Marsh fern --

Toxicodendron radicans Eastern poison ivy --

Typha latifolia Broadleaf cattail OBL

Ulmus americana American elm FACW

Utricularia foliosa Leafy bladderwort OBL

Utricularia purpurea Eastern purple bladderwort OBL

Utricularia inflata Floating bladderwort OBL

Vitis rotundifolia Muscadine --

Woodwardia virginica Virginia chain fern FACW

Xyris fimbriata Fringed yelloweyed grass OBL

1Florida Department of Environmental Protection Wetland Evaluation and Delineation Program, accessed 

June 28, 2004, at http://www.dep.state.flus/water/wetlands/delineation/vegindex/vegindex/htm.

2Wunderlin, R.P., and B.F., Hansen, 2004, Atlas of Florida Vascular Plants (http://www.plantatlas.usf.edu/). 

[S.M., Landry and K.N., Campbell (application development), Florida Center for Community Design and 

Research]. Institute for Systematic Botany, University of South Florida, Tampa, accessed June 28, 2004.

Appendix 12. Names and status of wetland plants identified in fixed plots at wetland sites. (Continued)

[sp., species; --, not determined; FACW, facultative wet; FAC, facultative; OBL, obligate]

Scientific name Common name Status1,2
Appendix 13. Comparison of National Wetlands Inventory (NWI)

and U.S. Geological Survey (USGS) wetland area estimates.

Wetland

NWI 

area estimate

(acres)

USGS

area estimate

(acres)

Percent 

difference 

between NWI 

and USGS area 

estimates

Duck Pond Marsh 6.5 5.2 -25

Green Swamp Cypress 1.8 1.7 -6

Green Swamp Marsh 2.0 1.6 -25

Hillsborough River State

Park Marsh

1.7 2.2 23

S-63 Cypress 1.2 1.3 8

S-68 Cypress 5.8 5.8 0

W-03 Marsh 7.8 7.4 -5

W-05 Cypress 8.6 8.8 2

W-29 Marsh 4.2 6.5 35

Total: 39.6 40.5 2

Appendixes 49