Distribution and Abundance of Submersed 

Aquatic Vegetation in the Tidal Potomac River and 

Upper Potomac Estuary, Maryland, Virginia, and 

the District of Columbia, 1993-1998

By Henry A. Ruhl, Nancy B. Rybicki, Justin T. Reel, and 

Virginia Carter

US Geological Survey

Open-File Report 99-233

science 

uses

for a changing world

Reston, Virginia 

1999
U. S. DEPARTMENT OF THE INTERIOR 

BRUCE BABBITT, Secretary

U. S. GEOLOGICAL SURVEY 

Charles G. Groat, Director

For additional information write to:

Chief, Vegetation and Hydrogeomorphic

Relations

U.S. Geological Survey

MS 430- National Center

Reston, Virginia 20192

Copies of this report may be purchased from:

U.S. Geological Survey 

Branch of Information Services 

Box 25286, Federal Center 

Denver, Colorado 80225-0286
CONTENTS

Page

Abstract 1

Introduction 1

Mapping methods 2

Acknowledgments 2

References cited 4

ILLUSTRATIONS

1993

Figures 1-3. Maps showing distribution and abundance of Hydrilla verticillata in 

the Potomac River, 1993

1. Washington, D.C. to Broad Creek 7

2. Swan Creek to Chicamuxen Creek 8

3. Chicamuxen Creek to Aquia Creek 9

Figures 4-5. Maps showing distribution and abundance of submersed aquatic 

vegetation in the Potomac River, 1993

4. Washington, D.C. to Quantico, Virginia 10

5. Quantico, Virginia to Aquia Creek 11

1994

Figures 6-8. Maps showing distribution and abundance of Hydrilla verticillata in 

the Potomac River, 1994

6. Washington, D.C. to Broad Creek 12

7. Swan Creek to Chicamuxen Creek 13

8. Chicamuxen Creek to Maryland Point 14

Figures 9-10. Maps showing distribution and abundance of submersed aquatic 

vegetation in the Potomac River, 1994

9. Washington, D.C. to Quantico, Virginia 15

10. Quantico, Virginia to Maryland Point 16

1995

Figures 11-13. Maps showing distribution and abundance of Hydrilla verticillata 

in the Potomac River, 1995

11. Washington, D.C. to Broad Creek 17

12. Swan Creek to Chicamuxen Creek 18

13. Chicamuxen Creek to Maryland Point 19
Figures 14-15. Maps showing distribution and abundance of submersed aquatic 

vegetation in the Potomac River, 1995

14. Washington, D.C. to Quantico, Virginia 20

15. Quantico, Virginia to Maryland Point 21

1996

Figures 16-18. Maps showing distribution and abundance of Hydhlla verticillata 

in the Potomac River, 1996

16. Washington, D.C. to Broad Creek 22

17. Swan Creek to Chicamuxen Creek 23

18. Chicamuxen Creek to Maryland Point 24

Figures 19-21. Maps showing distribution and abundance of submersed aquatic 

vegetation in the Potomac River, 1996

19. Washington, D.C. to Broad Creek 25

20. Swan Creek to Chicamuxen Creek 26

21. Chicamuxen Creek to Maryland Point 27

1997

Figures 22-24. Maps showing distribution and abundance of Hydrilla verticillata 

in the Potomac River, 1997

22. Washington, D.C. to Broad Creek 28

23. Swan Creek to Chicamuxen Creek 29

24. Chicamuxen Creek to Rt. 301 Bridge 30

Figures 25-27. Maps showing distribution and abundance of submersed aquatic 

vegetation in the Potomac River, 1997

25. Washington, D.C. to Broad Creek 31

26. Swan Creek to Chicamuxen Creek 32

27. Chicamuxen Creek to Rt. 301 Bridge 33

1998

Figures 28-30. Maps showng distribution and abundance of Hydrilla verticillata in 

the Potomac River, 1998

28. Washington, D.C. to Broad Creek 34

29. Swan Creek to Chicamuxen Creek 35

30. Chicamuxen Creek to Maryland Point 36

Figures 31-33. Maps showing distribution and abundance of submersed aquatic 

vegetation in the Potomac River, 1998

31. Washington, D.C. to Broad Creek 37

32. Swan Creek to Chicamuxen Creek 38

33. Chicamuxen Creek to Maryland Point 39

IV
DISTRIBUTION AND ABUNDANCE OF SUBMERSED AQUATIC VEGETATION

IN THE TIDAL POTOMAC RIVER AND UPPER POTOMAC ESTUARY, 

MARYLAND, VIRGINIA, AND THE DISTRICT OF COLUMBIA, 1993-1998

By Henry A. Ruhl, Nancy B. Rybicki, Justin T. Reel, and Virginia Carter

ABSTRACT

The U.S. Geological Survey determined submersed aquatic vegetation 

distribution and abundance in the tidal Potomac River and upper Potomac 

Estuary annually from 1993-1998. Observations were made on the location and 

abundance of submersed aquatic vegetation and the relative coverage of species 

present at the end of the growing season. The survey area extended from Chain 

Bridge in Washington, D.C. to Maryland Point, or as far downstream as the 

Route 301 Bridge depending on annual research needs. A set of 1:24,000-scale 

maps was created in the field and laboratory using aerial photographs and 

shoreline survey data collected over a period of several weeks. A set of smaller 

scale maps was also created to summarize the distribution and abundance of 

submersed aquatic vegetation and Hydrilla verticillata in the tidal Potomac River 

and upper Potomac Estuary.

INTRODUCTION

Submersed aquatic vegetation (SAV) is an important part of the food web 

in the Chesapeake Bay, providing shelter and nursery grounds for shellfish and 

finfish of commercial importance, as well as food for a diversity of waterfowl. 

SAV disappeared from the freshwater tidal Potomac River in the late 1930's 

(Carter and others, 1985). In the early 1980's, as water quality improved, many 

species of SAV returned (Carter and Rybicki, 1986, Rybicki and others, 1985). A 

southeast Asian species, Hydrilla verticillata, invaded the tidal Potomac River 

with the return of SAV, and populations of this exotic species increased 

dramatically in the mid to late 1980's. H. verticillata can be very dense in shallow 

areas, where it interferes with boat traffic, and the U.S. Army Corps of Engineers 

(COE), local, and state agencies began a harvesting program in the mid 1980's 

to provide boaters with access through the H. verticillata beds to boat moorings 

and marinas.

U.S. Geological Survey (USGS) researchers monitored the distribution 

and abundance as well as species composition of submersed aquatic vegetation 

(SAV) in the tidal Potomac River and Estuary beginning in 1978 (Carter and 

others 1985; Rybicki and others 1986; 1987). The USGS documented changes 

in SAV after the resurgence in SAV and provided information to many agencies, 

including the COE's Aquatic Plant Management Program. A series of 1:24,000-
scale field data maps and small-scale summary maps of SAV field survey results 

were produced annually.

This report summarizes the observations on SAV distribution and 

abundance, including Hydrilla verticillata, for the period 1993-1998. These data 

are used by the Potomac Aquatic Plant Control Program for the Metropolitan 

Washington Council of Governments, the D. C. Department of Consumer and 

Regulatory Affairs: Fisheries Division, the Virginia Institute of Marine Science 

(VIMS), the COE, and the Chesapeake Bay Program to study SAV ecosystem 

dynamics and to meet local and regional aquatic plant management needs. 

Annual SAV coverage (in hectares) as well as species present in the survey area 

are available on the Internet from VIMS (Orth and others, 1993-98; 

http://www.vims.edu/bio/sav).

MAPPING METHODS

The distribution and abundance of SAV, including H. verticillata, were 

determined by shoreline survey from a shallow draft boat and the use of aerial 

photographs. The shoreline survey was conducted annually at the end of the 

growing season -- late August through early October. The northern extent of the 

survey area was at Chain Bridge in the Potomac and near Kingman Island in the 

Anacostia River. The southern end of the survey area was between Aquia Creek 

and the Route 301 Bridge, with the extent depending on specific annual research 

needs. The area surveyed included all navigable tidal tributaries in the reach. 

Field observations on the location, percent cover of vegetation, and percent of 

each species in each bed encountered were made within two hours of low tide 

and were recorded on 1:24,000-scale maps (unpublished data). A metal rake 

was used to scrape along the bottom to check for the presence of species not 

visible from the surface and to confirm that plants were rooted and not simply 

floating (Rybicki and others, 1987). Aerial photographs (1:12,000 and 1:24,000 

scale) were obtained annually and were used in the field and in the lab to assist 

in the delineation of SAV bed boundaries and determination of plant density. A 

set of smaller scale maps (Figures 1-33) were then created from the 1:24,000- 

scale maps to illustrate the overall SAV and H. verticillata distribution and 

abundance. These smaller scale maps are theme products, and SAV coverages 

are not exactly to scale.

ACKNOWLEDGMENTS

Observation data for the D.C. area for 1996-1998 were provided by Adam 

Rottman, D. C. Department of Consumer and Regulatory Affairs: Fisheries 

Division. Aerial photographs were provided by Metropolitan Washington Council 

of Governments and the Virginia Institute of Marine Science. Support and
assistance was provided by the Metropolitan Washington Council of 

Governments and the U.S. Army Corp of Engineers.
REFERENCES CITED

Carter, Virginia, Paschal, J. E., and Bartow, Nancy, 1985, Distribution and

abundance of submersed aquatic vegetation in the tidal Potomac River, 

Maryland, Virginia, May 1978 to November 1981: U.S. Geological Survey 

Water-Supply Paper 2234-A, 46 p.

Carter, Virginia, and Rybicki, N. B., 1986, Resurgence of submersed aquatic

macrophytes in the tidal Potomac River, Maryland, Virginia, and District of 

Columbia: Estuaries, v. 9, no. 4B, p. 368-375.

Orth, R. J., Nowak, J. N., Anderson, G. F., and Whiting, J. R, 1993, Distribution 

of submerged aquatic vegetation in the Chesapeake Bay and tributaries 

and Chincoteague Bay- 1992: Virginia Institute of Marine Science, The 

College of William and Mary, Gloucester Point, Va., 268 p.

________, 1994, Distribution of submerged aquatic vegetation in the

Chesapeake Bay and tributaries and Chincoteague Bay- 1993: Virginia 

Institute of Marine Science, The College of William and Mary, Gloucester 

Point, Va., 262 p.

Orth, R. J., Nowak, J. N., Anderson, G. F., Wilcox, D. J., Whiting, J. R., and 

Nagey, L. S., 1995, Distribution of submerged aquatic vegetation in the 

Chesapeake Bay and tributaries and Chincoteague Bay- 1994: Virginia 

Institute of Marine Science, The College of William and Mary, Gloucester 

Point, Va., 277 p.

________, 1996, Distribution of submerged aquatic vegetation in the

Chesapeake Bay and tributaries and Chincoteague Bay- 1995: Virginia 

Institute of Marine Science, The College of William and Mary, Gloucester 

Point, Va., 293 p.

Orth, R. J., Nowak, J. N., and Wilcox, D. J., 1997, Distribution of submerged 

aquatic vegetation in the Chesapeake Bay and tributaries and coastal 

bays - 1996: Virginia Institute of Marine Science, The College of William 

and Mary, Gloucester Point, Va., 300 p.

Orth, R. J., Nowak, J. N., Wilcox, D. J., Whiting, J. R., and Nagey, L. S., 1998, 

Distribution of submerged aquatic vegetation in the Chesapeake Bay and 

tributaries and coastal bays, 1997: Virginia Institute of Marine Science, 

The College of William and Mary, Gloucester Point, Va., 351 p.

Rybicki, N. B., Anderson, R. T., Shapiro, J. M., Jones, C. L., and Carter, Virginia, 

1986, Data on the distribution and abundance of submersed aquatic 

vegetation in the tidal Potomac River, Maryland, Virginia, and the District 

of Columbia, 1985: U.S. Geological Survey Open-File Report 86-126, 49

PRybicki, N. B., Anderson, R. T., Shapiro, J. M., Johnson, K. L., and Schulman, C.

L., 1987, Data on the distribution and abundance of submersed aquatic 

vegetation in the tidal Potomac River, Maryland, Virginia, and the District 

of Columbia, 1986: U.S. Geological Survey Open-File Report 87-575, 82 

P-
Rybicki, N. B., Carter, Virginia, Anderson, R. T., and Trombley, T. J., 1985,

Hydrilla verticillata in the tidal Potomac River, Maryland, Virginia, and the 

District of Columbia, 1983 and 1984: U.S. Geological Survey Open-File 

Report 85-77, 26 p.

39°

77°15' 77°

38°45'

EXPLANATIONPercent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1993

 I 70-100

 I 40-70 II 10-40 

II 0-10

VIRGINIA

10 MILES

I 

10 KILOMETERS

MARYLAND 

Figure 1. Distribution and abundance of Hydrilla verticillata for the Potomac River u s Geological survey-shoreiine survey Data 

from Washington, D.C. to Broad Creek, 1993.
77°15' 77°

00

38°30'

MARYLAND

Nelson Point EXPLANATION 

End of Survey Percent cover of Hydrilla verticillata in 

Mattawoman submersed aquatic vegetation-1993 

H 70-100 

H 40-70

I I 10-40

II 0-10

10 MILES

\ 

10 KILOMETERS

Figure 2. Distribution and abundance of Hydrilla verticillata for the Potomac River u s Geological survey-shoreline survey Data 

from Swan Creek to Chicamuxen Creek, 1993.
77°15'

38°30'

38° 15'

77°

Popes 

reek

EXPLANATIONPercent cover of Hydrilla verticillata in

submersed aquatic vegetation-1993

H 70-100

H ^O - 70

I I 10-40 o

d]0-10 T10 KILOMETERS

Figure 3. Distribution and abundance of Hydrilla verticillata for the 

Potomac River from Chicamuxen Creek to Aquia Creek, 1993.

U.S. Geological Survey-Shoreline Survey Data
77°15'

38°45' 

EXPLANATION 

Percent cover of submersed 

aquatic vegetation-1993

 1 70-100

38°30' 

U.S. Geological Survey-Shoreline Survey Data

Figure 4. Distribution and abundance of submersed aquatic vegetation for the 

Potomac River from Washington, D.C. to Quantico, Virginia 1993.

10
EXPLANATION 

Percent cover of submersed 

aquatic vegetation-1993

 I 70-100

Figure 5. Distribution and abundance of submersed aquatic vegetation 

for the Potomac River from Quantico, Virginia to Aquia Creek, 1993.

U.S. Geological Survey-Shoreline Survey Data
39

77° 15'

38°45' 

EXPLANATION

Percent cover of Hydrilla verticillata in

submersed aquatic vegetation-1994

70-100

40-70 

dl 10-40 

II 0-10

VIRGINIA

10 MILES

10 KILOMETERS

MARYLAND 

Figure 6. Distribution and abundance of Hydrilla verticillata for the Potomac River us Geological Survey-Shoreline s^ Data 

from Washington, D.C. to Broad Creek, 1994.
77° 15' 77°

co

38°30'

MARYLAND

EXPLANATION

Percent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1994

70-100

40-70

CZ3 10-40II 0-10

5 10 MILES

10 KILOMETERS

Figure 7. Distribution and abundance of Hydrilla verticillata for the Potomac River u- s Geol°gicai survey-shoreline survey Data 

from Swan Creek to Chicamuxen Creek, 1994.
77°15' 77°

38°30'

38° 15'

EXPLANATION

Percent cover of Hydrilla verticillata in

submersed aquatic vegetation-1994

 I 70-100

40-70

I I 10-40 0

EH 0-10 n

10 KILOMETERS

Popes 

Creek

Figure 8. Distribution and abundance of Hydrilla verticillata for the 

Potomac River from Chicamuxen Creek to Maryland Pt., 1994.

U.S. Geological Survey-Shoreline Survey Data
77° 15' 77°

38°45' 

38°30'

EXPLANATION 

Percent cover of submersed 

aquatic vegetation-1994

^M 70-100

U.S. Geological Survey-Shoreline Survey Data

Figure 9. Distribution and abundance of submersed aquatic vegetation for the 

Potomac River from Washington, D.C. to Quantico, Virginia, 1994.

15
77°15

38"1S

EXPLANATION 

Percent cover of submersed 

aquatic vegetatlon-1994

^1 70-100 

40-70 

10-40 

I 1-10

U.S. Geological Survey-Shoreline Survey Data

Figure 10. Distribution and abundance of submersed aquatic vegetation 

for the Potomac River from Quantico, Virginia to Maryland Point, 1994.
39C 77° 15' 770

38°45'

EXPLANATION

Percent cover of Hydrilla verticillata inareas of submersed aquatic vegetation-1995

70-100

40-70

I I 10-40

II 0-10

VIRGINIA

10 MILES

J

10 KILOMETERS

MARYLAND 

Figure 11. Distribution and abundance of Hydrilla verticillata for the Potomac River u s Geological Survev-Shoreline Su y Da" 

from Washington, D.C. to Broad Creek, 1995.
77° 15'

CO

38°30' 

Gunston 

Cove 

Bellmont 

Bay

EXPLANATIONPercent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1995

70-100 

40-70 

10-40 

II 0-10

Figure 12. Distribution and abundance of Hydrilla verticillata for the Potomac River u-s - Geol°gical survey-sh0reiine survey Data 

from Swan Creek to Chicamuxen Creek, 1995.
77° 15'

38°30' 

38° 15'

Chicamuxen 

Creek

U.S. Highway 301 Bridge

EXPLANATION

Percent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1995

^m 40-70 

II 10-40 

II 0-10 10 KILOMETERS

Figure 13. Distribution and abundance of Hydrilla verticillata for the Potomac River from Chicamuxen Creek to Maryland Point, 1995.

U.S. Geological Survey-Shoreline Survey Data
38°45' 

EXPLANATION 

Percent cover of submersed 

aquatic vegetation-1995

 I 70-100

38C30' 

U.S. Geological Survey-Shoreline Survey Data

Figure 14. Distribution and abundance of submersed aquatic vegetation for the 

Potomac River from Washington, D.C. to Quantico, Virginia 1995.

20
77"15'

38°30' 

38°15'

EXPLANATION 

Percent cover of submersed 

aquatic vegetation-1995

 I 70-100

U.S. Geological Survey-Shoreline Survey Data

Figure 15. Distribution and abundance of submersed aquatic vegetation 

for the Potomac River from Quantico, Virginia to Maryland Point, 1995
ro 

ro

39

77° 15' 77c

38°45' 

EXPLANATION

Percent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1996

 I 70-100

40-70 

I I 10-40

FI 0-10

VIRGINIA

10 MILES

10 KILOMETERS

MARYLAND

Figure 16. Distribution and abundance of Hydrilla verticillata for the Potomac River 

from Washington, D.C. to Broad Creek, 1996.

U.S. Geological Survey-Shoreline Survey Data
77° 15'

ro

CO

38°30' 

Gunston 

Cc

Bellmont

EXPLANATIONPercent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1996

Nelson Point 

End of Survey 

Mattawoman 

Creek 1 70-100

40-70

CZH 10-40

II 0-10 Chicamuxen Creek

10 KILOMETERS

Figure 17. Distribution and abundance of Hydrilla verticillata for the Potomac River us Geol°sical survey-shore^ sum 

from Swan Creek to Chicamuxen Creek, 1996.
77° 15'

38°30'

U.S. Highway 301 

Bridge

Somerset Beach

VIRGINIA

EXPLANATIONPercent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1996

1H 70-100

 1 40-70I I 10-40II 0-10 10 KILOMETERS

Figure 18. Distribution and abundance of Hydrilla verticillata for the 

Potomac River from Chicamuxen Creek to Maryland Point, 1996.

U.S. Geological Survey-Shoreline Survey Data
en

39' 77°15' IT

38°45'

EXPLANATIONPercent cover of submersed

aquatic vegetation-1996

70-10040-70 

I I 10-40 

I 1-10

VIRGINIA

10 MILES

J

5 10 KILOMETERS

MARYLAND

Figure 19. Distribution and abundance of submersed aquatic vegetation for the 

Potomac River from Washington, D.C. to Broad Creek, 1996.

U.S. Geological Survey-Shoreline Survey Data
77° 15' 77°

ro 

en

38°30'

MARYLAND

EXPLANATIONPercent cover of submersed

aquatic vegetation -1996

70-100

40-70 

10-40

1 -10

10 MILES

\ 

10 KILOMETERS

Figure 20. Distribution and abundance of submersed aquatic vegetation for the 

Potomac River from Swan Creek to Chicamuxen Creek, 1996.

U.S. Geological Survey-Shoreline Survey Data
77° 15' 77°

38°30'

no

38° 15'

Popes 

Creek

EXPLANATIONPercent cover of submersed

aquatic vegetaton-1996

^| 70 -100

40-70

CU 10-40

CD 1-10 10 KILOMETERS

Figure 21. Distribution and abundance of submersed aquatic vegetation 

for the Potomac River from Chicamuxen Creek to Maryland Point, 1996.

U.S. Geological Survey-Shoreline Survey Data
39' 77°15' IT

ro

CO

38°45'

EXPLANATIONPercent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1997

70-100

40-70

I I 10-40

II 0-10

NationaNA OAirport V ^ A } o

VIRGINIA

10 MILES

j

10 KILOMETERS

MARYLAND 

Figure 22. Distribution and abundance of Hydrilla verticillata for the Potomac River us- GeologicalSurvey-shorelineSurvey Data 

from Washington, D.C. to Broad Creek, 1997.
77°15' IT

ro

38°30'

MARYLAND

Gunston

Cove 

Bellmont 

Bay

Mason Neck

End of Survey

Mattawoman 

Creek

EXPLANATION

Percent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1997

70-100

40-70 

GH 10-40 

f~~"l 0-10 

^ No Data

10 MILES

10 KILOMETERS

Figure 23. Distribution and abundance of Hydrilla verticillata for the Potomac River 

from Swan Creek to Chicamuxen Creek, 1997.

U.S. Geological Survey-Shoreline Survey Data
77°15' 77°

CJo

38° 15'

Popes 

Creek

EXPLANATIONPercent cover of Hydrilla verticillata in

submersed aquatic vegetation-1997

 1 70-100

40-70

I I 10-40

EH 0-10 °____

m% No Data 0

Somerset Beach

VIRGINIA

10 MILES

_|

10 KILOMETERS

Figure 24. Distribution and abundance of Hydrilla verticillata for the Potomac River from Chicamuxen Creek to Rt. 301 Bridge, 1997.

U.S. Geological Survey-Shoreline Survey Data
39' 77°15' IT

38°45'

EXPLANATIONPercent cover of submersed

aquatic vegetation-1997

70-100

40-70 

I I 10-40

I I 1 -10

VIRGINIA

10 MILES

I

10 KILOMETERS

Dyke

Marsh

MARYLAND 

Figure 25. Distribution and abundance of submersed aquatic vegetation for the Potomac River from Washington, D.C. to Broad Creek, 1997.

U.S. Geological Survey-Shoreline Survey Data
77° 15' 77°

GO

ro

38°30'

MARYLAND

Gunston 

Cove

Bellmont 

Bay

Mason Neck

jv Nelson Point 

End of Survey

v \ Mattawoman 

Creek

EXPLANATION

Percent cover of submersed

aquatic vegetation-1997

70-100

40-70 

CZ] 10-40

cm 1-10

10 MILES 

I

10 KILOMETERS

Figure 26. Distribution and abundance of submersed aquatic vegetation for the Potomac River from Swan Creek to Chicamuxen Creek, 1997.

U.S. Geological Survey-Shoreline Survey Data
77° 15'

38°30'

CO CO

38°15

77°

v Chicamuxen 

Creek

EXPLANATIONPercent cover of submersed

aquatic vegetation-1997

 I 70-100

40-70 

I I 10-40 

I I 1 -10 10 KILOMETERS

Figure 27. Distribution and abundance of submersed aquatic vegetation 

for the Potomac River from Chicamuxen Creek to Rt. 301 Bridge, 1997.

U.S. Geological Survey-Shoreline Survey Data
CO

39

77° 15' 77c

38°45'

EXPLANATIONPercent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1998

70-10040-70

I I 10-40

II 0-10 

^ No Data

VIRGINIA

10 MILES

I

10 KILOMETERS

MARYLAND 

Figure 28. Distribution and abundance of Hydrilla verticillata for the Potomac River us. Geological survey-shoreline survey Data 

from Washington, D.C. to Broad Creek, 1998.
77° 15' 77°

CO01

38°30'

MARYLAND

End of Survey 

Mattawoman EXPLANATION

Creek Percent cover of Hydrilla verticillata in

areas of submersed aquatic vegetation-1998

70-10040-70 

I I 10-40

II 0-10 

iMl No Data

10 MILES

10 KILOMETERS

Figure 29. Distribution and abundance of Hydrilla verticillata for the Potomac River u.s. Geological survey.shoreiinesurvey Data 

from Swan Creek to Chicamuxen Creek, 1998.
77° 15'

COcn

Chicamuxen 

Creek

Wades 

Bay

Smith 

Point

U.S. Highway 301 Bridge

Somerset Beach

VIRGINIA EXPLANATION Percent cover of Hydrilla verticillata in 

submersed aquatic vegetation-1998 

70-100

40-70 

10-40 

II 0-10 

No Data 10 KILOMETERS

Figure 30. Distribution and abundance of Hydrilla verticillata for the 

Potomac River from Chicamuxen Creek to Maryland Pt., 1998.

U.S. Geological Survey-Shoreline Survey Data
39' 77°15'

Co

38°45'

77°

EXPLANATIONPercent cover of submersed

aquatic vegetation- 1998

70-100 

^ 40-70 

10-40

No data

VIRGINIA

5 10 KILOMETERS

MARYLAND

Figure 31. Distribution and abundance of submersed aquatic vegetation for the 

Potomac River from Washington, D.C. to Broad Creek, 1998.

U.S. Geological Survey-Shoreline Survey Data
77° 15' 77°

GO00

38°30'

MARYLAND

.Nelson Point 

End of Survey

Mattawoman

EXPLANATIONPercent cover of submersed

aquatic vegetation-1998

70-100

40-70 

EH 10-40

I I 1-10

iH No Data

10 MILES

10 KILOMETERS

Figure 32. Distribution and abundance of submersed aquatic vegetation for the Potomac River from Swan Creek to Chicamuxen Creek, 1998.

U.S. Geological Survey-Shoreline Survey Data
77° 15'

38°30'

CO

38° 15'

77°

Popes 

Creek

EXPLANATION

Percent cover of submersed

aquatic vegetation-1998

70-10040-70 

I I 10-40

I I 1 -10

Wh No Data

10 KILOMETERS

Figure 33. Distribution and abundance of submersed aquatic vegetation 

for the Potomac River from Chicamuxen Creek to Maryland Point, 1998.

U.S. Geological Survey-Shoreline Survey Data