National Park Service

U.S. Department of the Interior

Natural Resource Program Center

Rock Creek Park Natural Resource 

Condition Assessment

National Capital Region Network

Natural Resource Report NPS/NCRN/NRR—2009/109
b

N

0 0.5 mi 1 mi

95

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Potomac R.

Potomac R.

Chesapeake Bay

Shenandoah R.

Virginia

West

Virginia

Pennsylvania

Maryland

Blue Ridge

Baltimore

National Park

Appalachia

Blue Ridge

Piedmont

Coastal Plain

Washington

 D.C.

USA

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0 10 mi 20 mi

The 11 parks of the NPS National Capital Region Network are shown in red.

The DC-VA-MD region and Potomac River. Map: GoogleTM. Rock Creek Park. Map: NPS.

Rock Creek 

Park

Rock Creek 

Park

ON THE COVER

Aerial photo of Washington, D.C. on the left and Rock Creek Park on the right. Photo: Tom Paradis.

0 2.0 mi N
c

Dr. Tim Carruthers1, Dr. Shawn Carter2, Lisa N. Florkowski1, Dr. Jeff Runde3, 

and Dr. Bill Dennison4

1

 Integration & Application Network, University of Maryland Center for 

Environmental Science, P.O. Box 775, Cambridge, MD 21613

2

 National Capital Region Inventory & Monitoring, National Park Service,

4598 MacArthur Blvd, NW, Washington, D.C. 20007

3

 Crater Lake National Park, National Park Service, Crater Lake, OR 97604

4

 University of Maryland Center for Environmental Science, P.O. Box 775, 

Cambridge, MD 21613

May 2009

U.S. Department of the Interior

National Park Service

Natural Resource Program Center

Fort Collins, Colorado

Rock Creek Park Natural Resource 

Condition Assessment

National Capital Region Network

Natural Resource Report NPS/NCRN/NRR—2009/109
ii

The Natural Resource Publication series addresses natural resource topics that are of interest and 

applicability to a broad readership in the National Park Service and to others in the management 

of natural resources, including the scientifi c community, the public, and the NPS conservation and 

environmental constituencies. Manuscripts are peer-reviewed to ensure that the information is 

scientifi cally credible, technically accurate, appropriately written for the intended audience, and is 

designed and published in a professional manner.

Natural Resource Reports are the designated medium for disseminating high priority, current 

natural resource management information with managerial application. The series targets a 

general, diverse audience, and may contain NPS policy considerations or address sensitive issues 

of management applicability. Examples of the diverse array of reports published in this series 

include vital signs monitoring plans; monitoring protocols; “how to” resource management papers; 

proceedings of resource management workshops or conferences; annual reports of resource 

programs or divisions of the Natural Resource Program Center; resource action plans; fact sheets; 

and regularly published newsletters.

Views, statements, fi ndings, conclusions, recommendations and data in this report are solely those 

of the author(s) and do not necessarily refl ect views and policies of the U.S. Department of the 

Interior, National Park Service. Mention of trade names or commercial products does not constitute 

endorsement or recommendation for use by the National Park Service.

This report is available from http://ian.umces.edu/communication/reports/ and the Natural Resource 

Publications Management Web site from http://www.nature.nps.gov/publications/NRPM on the 

Internet.

Please cite this publication as:

Carruthers, T., S. Carter, L. Florkowski, J. Runde, and W. Dennison. 2009. Rock Creek Park natural 

resource condition assessment, National Capital Region Network. Natural Resource Report NPS/

NCRN/NRR—2009/109. National Park Service, Fort Collins, Colorado.

Acknowledgements

Jane M. Hawkey, Integration & Application Network, University of Maryland Center 

for Environmental Science, who provided science communication, layout, and 

design.

Geoff Sanders, Mark Lehman, Dr. John Paul Schmit, Marian Norris, and Pat 

Campbell, NPS National Capital Region Inventory & Monitoring, who provided 

data support. Staff at Rock Creek Park, especially Bill Yeaman, Ken Ferebee, and 

Adrienne Applewhaite-Coleman, for input, comments, and suggestions throughout 

the production of this Natural Resource Condition Assessment. The many NPS staff 

who provided insight and comments during the development of this assessment 

approach during workshops at the National Conservation and Training Center, 

October 2006, 2007, 2008. Staff at the Center for Urban Ecology who assisted with 

data sourcing, scoping, and proofi ng. The Water Resources Division of the NPS 

Natural Resources Program Center, who provided funding and direction.

NPS 100011, May 2009
iii

TABLES .......................................................................................................................................................vi

FIGURES ....................................................................................................................................................vii

EXECUTIVE SUMMARY .............................................................................................................................xi

Background ............................................................................................................................................................... xi

Natural resource condition assessment .................................................................................................................. xii

Ecological monitoring framework ......................................................................................................................... xiii

Recommendations based on habitat monitoring framework ............................................................................. xiv

Data gaps................................................................................................................................................................. xvi

Applicability of the natural resource condition assessment ............................................................................... xvii

Conclusions ............................................................................................................................................................. xvii

CHAPTER 1: INTRODUCTION .....................................................................................................................1

History of Rock Creek Park ........................................................................................................................................1

Mission, goals, and context .......................................................................................................................................3

Natural resource condition assessment ....................................................................................................................4

Literature cited (Chapter 1) .......................................................................................................................................5

CHAPTER 2: NATURAL RESOURCES ...........................................................................................................7

Introduction ...............................................................................................................................................................8

Data collection ...........................................................................................................................................................8

Geology ..........................................................................................................................................................................................8

Soils ................................................................................................................................................................................................8

Habitats ....................................................................................................................................................................10

Forest Habitat ..............................................................................................................................................................................10

Wetland (Inland) Habitat ............................................................................................................................................................14

Artifi cial-terrestrial Habitat ........................................................................................................................................................19

Literature cited (Chapter 2) .....................................................................................................................................20

CHAPTER 3: CURRENT & POTENTIAL STRESSORS ..................................................................................23

Introduction .............................................................................................................................................................24

Air quality .................................................................................................................................................................25

Water quality ...........................................................................................................................................................30

External stressors .........................................................................................................................................................................30

Within park evidence ..................................................................................................................................................................32

Surrounding landscape ............................................................................................................................................33

Watershed ...................................................................................................................................................................................33

Population ...................................................................................................................................................................................34

Roads ............................................................................................................................................................................................34

Impervious surface ......................................................................................................................................................................37

Literature cited (Chapter 3) .....................................................................................................................................39

CHAPTER 4: METRICS & THRESHOLDS ....................................................................................................41

Introduction .............................................................................................................................................................41

Utility of thresholds ....................................................................................................................................................................41

Defi nition and types of thresholds ............................................................................................................................................41

Process of threshold determination ...........................................................................................................................................42

Air Quality ................................................................................................................................................................47

Ozone—regulatory .....................................................................................................................................................................47

Wet nitrate deposition—ecological ...........................................................................................................................................47

Wet sulfate deposition—ecological ...........................................................................................................................................48

Contents
iv

Particulate matter (soot)—regulatory .......................................................................................................................................48

Mercury deposition—regulatory ................................................................................................................................................49

Water Quality ...........................................................................................................................................................50

pH, dissolved oxygen, temperature—regulatory ......................................................................................................................50

Acid neutralizing capacity—ecological ......................................................................................................................................50

Salinity—regulatory ....................................................................................................................................................................51

Nitrate—ecological .....................................................................................................................................................................51

Total phosphorus—ecological ....................................................................................................................................................51

Benthic index of biotic integrity—ecological ............................................................................................................................51

Physical habitat index—ecological .............................................................................................................................................52

Biodiversity ...............................................................................................................................................................52

Percent cover of herbaceous species, woody vines, and target exotic trees and shrubs)—management ............................52

Presence of pest species—management, ecological .................................................................................................................52

Native seedling regeneration—ecological ................................................................................................................................53

Fish index of biotic integrity—ecological ..................................................................................................................................53

Proportion of area occupied by adult amphibians—management .........................................................................................54

Presence of forest interior dwelling species of birds—ecological ...........................................................................................54

White-tailed deer density—forest: management, ecological; grassland: management ........................................................55

Ecosystem Pattern and Processes ............................................................................................................................56

Percent forest—ecological ..........................................................................................................................................................56

Critical dispersal threshold index—ecological ...........................................................................................................................56

Impervious surface—ecological ..................................................................................................................................................56

Literature cited (Chapter 4) .....................................................................................................................................57

CHAPTER 5: RESOURCE CONDITION ASSESSMENT ...............................................................................63

Introduction .............................................................................................................................................................63

Rock Creek assessment approach ...........................................................................................................................64

Methods....................................................................................................................................................................65

Ecological monitoring framework .............................................................................................................................................65

Habitat framework .....................................................................................................................................................................66

Data and thresholds ................................................................................................................................................68

Ecological monitoring framework .............................................................................................................................................68

Habitat framework .....................................................................................................................................................................71

Calculation of natural resource condition .............................................................................................................72

Ecological monitoring categories ..............................................................................................................................................72

Habitats ........................................................................................................................................................................................73

Use of habitat framework for calculating sub-park assessments ............................................................................................73

Results .......................................................................................................................................................................74

Ecological monitoring framework .............................................................................................................................................74

Habitat framework .....................................................................................................................................................................76

Discussion .................................................................................................................................................................78

Ecological monitoring framework .............................................................................................................................................78

Habitat framework .....................................................................................................................................................................79

Comparison of approaches .........................................................................................................................................................79

Data gaps .....................................................................................................................................................................................79

Literature cited (Chapter 5) .....................................................................................................................................79

Contents (continued)
v

CHAPTER 6: IMPLICATIONS ......................................................................................................................83

Use of natural resource condition assessment in an adaptive management cycle .............................................83

Use of the assessment framework to direct monitoring and decision making ...................................................84

Implementation strategy for Rock Creek resource condition assessment ...........................................................84

Prioritizing identifi ed research needs based upon management data gaps .......................................................87

APPENDIX A. RAW DATA USED IN ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table A.1. Ozone (ppm). Values that fail the threshold (0.075) are in bold ...................................................93

Table A.2. Total annual nitrate deposition (kg ha-1 yr-1). Thresholds are 15

for forest and 10 for other habitats .................................................................................................93

Table A.3. Annual wet sulfate deposition (kg ha-1 yr-1). Values that fail the

threshold (10) are in bold .................................................................................................................94

Table A.4. Particulate matter (soot; pm2.5 mg m-3). Values that fail the threshold (15) are in

bold .....................................................................................................................................................94

Table A.5. Annual Mean Hg Deposition (ng L-1). Values that fail threshold

(2.0) are in bold ..................................................................................................................................94

Table A.6. Water quality data. Values that exceed threshold are in bold .......................................................95

Table A.7. Benthic index of biotic integrity. Values that exceed threshold are

in bold ................................................................................................................................................101

Table A.8. Physical habitat index. Values that exceed threshold (> 42) are in bold .......................................101

Table A.9. Proportion (%) of cover of exotic shrubs, trees, and herbaceous plants. Values

that exceed threshold (> 5%) are in bold ........................................................................................102

Table A.10. Presence of forest pest species. Values that exceed threshold

(> 1%) are in bold ..............................................................................................................................103

Table A.11. Native seedling regeneration (seedlings ha-1). Values that do not

meet the threshold (31,875 ha-1) are in bold ...................................................................................103

Table A.12. Fish index of biotic integrity. Values that exceed threshold (> 3)

are in bold ..........................................................................................................................................103

Table A.13. Proportion (%) of area occupied by amphibians. Values that are

outside the threshold range (20-80%) are in bold ..........................................................................103

Table A.14. Presence of forest interior dwelling species of birds. Values that

do not meet the threshold (> 1 highly sensitive species; > 4 sensitive species)

are in bold ..........................................................................................................................................104

Table A.15. Deer density (deer km-2). Values that exceed the threshold

(forest: 8 km-2; grassland: 20 km-2) are in bold .................................................................................104

APPENDIX B. INFORMATION USED IN ROCK CREEK PARK NATURAL RESOURCE CONDITION

 ASSESSMENT

Table B.1. IUCN Habitats Classifi cation Scheme (Version 3.0)—

www.iucnredlist.org/static/major_habitats ......................................................................................105

Table B.2. Exotic herbaceous species found in Rock Creek Park ......................................................................107

Table B.3. Reports for I&M data used in the natural resource condition assessment ....................................108

Table B.4. Participants at the data scoping workshop held at the Center for

Urban Ecology on June 20th, 2006 ...................................................................................................109

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C.,

based on a query of NPS NatureBib made on November 26, 2008. Brief abstract

information is provided. Citations not having a date or author are not shown ..........................109

Table B.6. List of acronyms .................................................................................................................................132

Contents (continued)
vi

Tables

Table 2.1. Fish species and number of individuals captured during annual

park surveys (2002-2005) ...................................................................................................................17

Table 4.1. Thresholds for Air Quality metrics ....................................................................................................43

Table 4.2. Thresholds for Water Quality metrics ..............................................................................................44

Table 4.3. Thresholds for Biodiversity metrics ...................................................................................................45

Table 4.4. Thresholds for Ecosystem Pattern and Processes metrics ................................................................46

Table 5.1. Summary of IUCN major habitat classifi cations (for full listing, see

Appendix Table B.1) ...........................................................................................................................66

Table 5.2. Summary of data used in Rock Creek Park natural resource condition

assessment ..........................................................................................................................................69

Table 5.3. Sources of data used in Rock Creek Park natural resource condition

assessment ..........................................................................................................................................70

Table 5.4. Summary of data used in Rock Creek Park habitat-based

natural resource condition assessment ............................................................................................72

Table 5.5. Categorical ranking of threshold attainment categories ...............................................................73

Table 5.6. Summary natural resource condition assessment for Rock Creek Park by

metric categories ...............................................................................................................................75

Table 5.7. Summary of Rock Creek Park habitat-based natural resource condition assessment ..................76

Table 5.8. Habitat-based natural resource condition assessment within

sub-regions of Rock Creek Park ........................................................................................................78

Table 6.1. Key fi ndings, implications, and recommendations resulting from

Rock Creek natural resource condition assessment.........................................................................85

Table 6.2. Data gaps and associated research needs resulting from Rock

Creek natural resource condition assessment..................................................................................88
vii

Figure 2.1. Conceptual diagram illustrating the key natural resources of Rock

Creek Park, Washington, D.C. ...........................................................................................................7

Figure 2.2. GIS data layer of geologic faults and bedrock geology for Rock

Creek Park, Washington, D.C. ...........................................................................................................9

Figure 2.3. GIS data layer of soil types found in Rock Creek Park,

Washington, D.C. ...............................................................................................................................9

Figure 2.4. GIS data layer of major habitat types in Rock Creek Park,

Washington, D.C., as defi ned by aggregation of vegetation in

Figure 2.6 ............................................................................................................................................10

Figure 2.5. Sampling sites for fauna and forest vegetation within Rock Creek Park ......................................11

Figure 2.6. GIS data layer of predominant vegetation types for Rock Creek

Park, Washington, D.C. ......................................................................................................................12

Figure 2.7. Extent of forest and non-forest landcover (Landsat 30 m)

within and around Rock Creek Park, Washington, D.C. for 2000 ..................................................13

Figure 2.8. Stream monitoring locations (n=10) used for long-term water

quality monitoring at Rock Creek Park, Washington, D.C. .............................................................15

Figure 2.9. GIS data layer depicting a portion of the stream network for

Rock Creek Park, Washington, D.C. Upstream tributaries

(Montgomery County, MD) are also shown .....................................................................................15

Figure 2.10. GIS data layer of topographic elevation for Rock Creek Park,

Washington, D.C. ...............................................................................................................................16

Figure 2.11. GIS data layer depicting the location of seeps and springs (n=15)

in Rock Creek Park, Washington, D.C. ..............................................................................................16

Figure 2.12. Median, minimum, and maximum monthly pH values for 10

stream sampling locations (see Figure 2.8) from 2005-2007 in

Rock Creek Park, Washington, D.C. Acceptable ranges

(6.0  pH  8.5) are shown.................................................................................................................18

Figure 2.13. Median, minimum, and maximum monthly dissolved oxygen

concentration (mg L-1) for 10 stream sampling locations (see

Figure 2.8) from 2005-2007 for Rock Creek Park, Washington,

D.C. Acceptable ranges (DO  3.2 mg L-1 from Jan-Jun, DO 

5.0 mg L-1 from Feb-May) are shown ................................................................................................18

Figure 2.14. Median, minimum, and maximum monthly acid neutralizing

capacity (ANC; mg CaCO3 L-1) for 10 stream sampling locations

(see Figure 2.8) from 2005-2007 for Rock Creek Park,

Washington, D.C. Acceptable range (mg CaCO3

 L-1 

10 mg L-1) is shown ............................................................................................................................18

Figure 2.15. Median, minimum, and maximum monthly water temperature

(°C) with standard deviation for 10 stream sampling locations

(see Figure 2.8) from 2005-2007 for Rock Creek Park,

Washington, D.C. Acceptable range (temp.  32.2°C) is shown .....................................................18

Figures
viii

Figures

Figure 3.1. Conceptual diagram illustrating the major environmental stressors

facing Rock Creek Park, Washington, D.C. ......................................................................................23

Figure 3.2. Map of sampling stations used for measuring ambient air

quality near Rock Creek Park, Washington, D.C. .............................................................................25

Figure 3.3. Hourly atmospheric ozone concentration (8-hr mean ppm) from

1994-2003 at the southeast end of McMillan Reservoir (see

Figure 3.2), Washington, D.C. Acceptable range (8-hr mean

 0.075 ppm) is shown .......................................................................................................................26

Figure 3.4. Annual wet nitrate deposition (mg L-1) from 1984-2007 for

sites MD99, MD03, and VA10 (see Figure 3.2.). Acceptable

ranges for forest (NO3

-  15 kg ha-1 yr-1) and cultivated (NO3-

 15 kg ha-1 yr-1) habitats are shown .................................................................................................26

Figure 3.5. Mean annual wet sulfate deposition (mg L-1) from 1984-2007

for sites MD99, MD03, and VA10 (see Figure 3.2), Washington,

D.C. Acceptable range (SO4

-2  18 kg ha-1 yr-1) is shown ..................................................................27

Figure 3.6. Mean monthly mercury (Hg) concentration (ng L-1) at Beltsville

Agricultural Research Center (see Figure 3.2) in Beltsville, MD.

Acceptable range (Hg  2 ng L-1) is shown .......................................................................................27

Figure 3.7. Total wet sulfate (SO4

-2) deposition (kg ha-1) for the

continental United States in 2006 ....................................................................................................27

Figure 3.8. Total wet mercury (Hg) deposition (μg m-2) for the continental

United States in 2006 ........................................................................................................................28

Figure 3.9. Mean monthly particulate matter (soot; PM2.5) concentration

with standard deviation for sites 41, 42, and 43 from 1999-

2004. Sampling intensity increased after 2003 ................................................................................29

Figure 3.10. Comparisons in rise rate (cfs day-1) between time period prior

to (1930-1967) and after (1968-2007) Lake Needwood

reservoir construction. Data from USGS level logger at Sherrill

Drive in Rock Creek Park, Washington, D.C. ....................................................................................29

Figure 3.11. GIS data layer of a portion of the Washington, D.C. sewer

system .................................................................................................................................................30

Figure 3.12. GIS data layer of point source inputs (combined sewer outfalls

and stormwater drains) to Rock Creek Park, Washington, D.C.

Two hundred seventeen sources are shown in this geographic

extent. A total of 342 are located in or adjoining the entire park

unit .....................................................................................................................................................30

Figure 3.13. GIS data layer showing 222 sites in and around Rock Creek Park,

Washington, D.C. that contain hazardous materials ......................................................................31

Figure 3.14. Median, maximum, and minimum monthly salinity

concentration for 10 stream sampling locations (See Figure

2.8) from 2005-2007 for Rock Creek Park, Washington, D.C.

Acceptable range (salinity < 0.25) is shown .....................................................................................32

Figure 3.15. Median, maximum, and minimum monthly nitrate (NO3

-

)

concentration (mg L-1) for 10 stream sampling locations (See

Figure 2.8) from 2005-2007 for Rock Creek Park, Washington,

D.C. Acceptable range (NO3

-  2.0 mg L-1) is shown .........................................................................32

Figures (continued)
ix

Figure 3.16. Median, maximum, and minimum monthly organic total

phosphorus (TP) concentration (μg L-1) for 10 stream sampling

locations (See Figure 2.8) from 2005-2007 for Rock Creek Park,

Washington, D.C. Acceptable range (P  37 μg L-1) is shown .........................................................32

Figure 3.17. GIS data layer showing the trail system of Rock Creek Park,

Washington, D.C. ...............................................................................................................................33

Figure 3.18. Population map derived from U.S. Census Bureau block

population estimates. Blocks were clipped to the subwatershed

boundary and the total population was estimated for each

subwatershed .....................................................................................................................................34

Figure 3.19. Road density was calculated by measuring the length of the

roads within the subwatershed boundary. The length was then

divided by the subwatershed area to produce density ...................................................................35

Figure 3.20. Stream density was calculated using the same method used for

road density. The ratio of road to stream density was then

calculated ...........................................................................................................................................36

Figure 3.21. GIS data layer showing percent impervious surface in and

around Rock Creek Park, Washington, D.C., in 2000 ......................................................................37

Figures (continued)

Figure 4.1. Conceptual relationship between ecosystem condition and the

different types of thresholds. In all cases, it is presumed that the

metric is well-studied with a reliable measurement protocol and

well-understood responses (e.g., available large spatio-temporal

data sets) ............................................................................................................................................41

Figure 5.1. Multiple spatial scales relevant to assessing natural resource conditions .....................................63

Figure 5.2. Conceptual framework for desired and degraded condition of

habitats present within Rock Creek Park, indicating metrics to

track status of condition ...................................................................................................................67

Figure 5.3. Defi ned management based sub-regions within Rock Creek Park ................................................73

Figure 5.4. Summary results of habitat-based Rock Creek Park natural resource

condition assessment .........................................................................................................................77

Figure 6.1. Example of how the natural resource condition assessment framework

can be applied to the adaptive management cycle within Rock

Creek Park and in association with community partners ...............................................................83
x

Tom Paradis

Rock Creek Park forest.
xi

Executive Summary

Background

Rock Creek Park, established in 1890, 

is one of the largest urban natural 

parks in the world and provides 

both recreational and ecological 

benefi ts to millions of visitors. Even 

though the park is 81% forested 

and has extensive stream and 

wetland habitat, it nevertheless 

faces many ecosystem challenges 

as a consequence of its urban 

surroundings. The park is located at 

the downstream end of an urban 

watershed, with some tributaries of 

Rock Creek surrounded by more than 

75% impervious surface.

In June of 2006, scoping efforts 

were initiated to compile existing 

natural resource data. Important 

sources of information used in this 

report include the products of shortterm research studies, long-term 

monitoring, baseline inventories, and 

mapping. Inventory and monitoring 

‘vital signs’ monitoring commenced 

within Rock Creek Park in 2003. This 

EXECUTIVE SUMMARY

program provided the core data 

utilized in this natural resource 

condition assessment. 

Rock Creek Park provides a wealth 

of natural resource values, largely 

resulting from the maintenance 

of forest and wetland habitats. 

The secondary growth forest, 

dominated by mixed beech and oak 

communities, functions as a regional 

refuge for forest dwelling bird 

species which have been showing 

regional declines. The large forest 

area also adds value to remnant 

forest patches surrounding the park, 

allowing for ecological connectivity 

between these fragments. Seep and 

spring habitats have been almost 

eliminated regionally with increased 

development, so the existence of 

these water resources in the park 

provides increasingly important 

habitat for native fauna and fl ora. 

Since being established, the park has 

provided a natural oasis for millions 

of visitors in the Washington D.C. 

area to enjoy. 

A woodland 

footbridge over Rock 

Creek. 

Lisa Florkowski
xii

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Rock Creek Park’s natural resources 

are challenged by multiple regional 

and local stressors. Air pollution 

from power plants, industry and 

vehicle emissions result in reduced air 

quality through large regions of the 

central eastern seaboard of North 

America. The urban Rock Creek 

Park is therefore subjected to high 

ozone and atmospheric deposition, 

potentially impacting fl ora, fauna 

and park visitors. Watershed wide 

urbanization and development 

result in challenges to water quality 

and quantity. Increased nutrients, 

pollutants and fl ashiness of river fl ow 

can result in impacts to wetland fl ora 

and fauna as well as stream bank 

erosion, respectively. Locally, Rock 

Creek Park has very high visitation 

and therefore has increased pressure 

to develop new paths and facilities 

would that potentially stress the 

connectivity of natural habitats. 

Natural resource condition 

assessment

Assessment of natural resource 

conditions within Rock Creek 

Park was carried out using two 

synthetic frameworks. Both were 

based on categories that addressed 

key structural and functional 

aspects of the ecosystem. The 

fi rst framework was an ecological 

monitoring framework based on 

the Inventory and Monitoring vital 

signs categorization of metrics. 

These 29 metrics were synthesized in 

four categories: Air Quality, Water 

Quality, Biodiversity, and Ecosystem 

Pattern and Processes. The second 

framework focused 21 metrics in 

the three dominant habitat types 

present within Rock Creek Park, 

Forest Habitat (81% of the area), 

Wetland (Inland) Habitat (2% of the 

area) and Artifi cial-terrestrial Habitat

(17% of the area). The synthetic 

assessment of condition was based 

on a comparison of available data 

collected between 2000 and 2008 to 

justifi ed ecological threshold values. 

The assessment was then presented 

in a conceptual framework of desired 

to degraded condition. 

Posted fencing 

protects a sensitive 

amphibian breeding 

area from people 

off trails and pets 

off leashes, but 

poor water quality 

can threaten their 

viability as well.

Sewage outfalls 

following rain events 

sends pollution to 

park streams, as this 

sign on zoo grounds 

forewarns.

Lisa Florkowski

Lisa Florkowski
xiii

EXECUTIVE SUMMARY

Ecological monitoring 

framework

The ecological monitoring 

framework showed that, within the 

park, Air Quality was generally in 

degraded condition, Water Quality

was highly variable but generally 

good, Biodiversity was generally fair, 

and Ecosystem Pattern and Processes

were generally good. In good 

condition according to indicators 

included: percent cover of forest 

habitat, percent impervious surface 

within park boundaries, amphibian 

occupancy, the presence of important 

forest interior bird species, and the 

lack of forest insect pests. Stream 

water quality showed mixed results. 

While several stream parameters 

(temperature, pH, dissolved oxygen 

concentration, and physical habitat) 

were found to be in good condition, 

other chemical components 

(salinity, nitrate concentration, 

total phosphorus concentration) 

seldom met threshold standards. 

Total phosphorus, in particular, 

was exceptionally high and always 

exceeded acceptable concentrations. 

Other areas of concern included 

native seedling regeneration, whitetailed deer densities, invasive exotic 

species, and several components of 

air quality (ozone concentration, 

particulate matter concentration, 

and mercury deposition). Decline 

in water quality, air quality, and 

stormwater management usually 

indicate regional or watershed 

changes rather than processes within 

the park boundaries alone. 

EXECUTIVE SUMMARY

This view across Rock 

Creek Park illustrates 

the periodic breaks 

in forest cover as the 

park is intersected by 

roads and bridges, 

and fragmented by 

urban and suburban 

development.

NPS
xiv

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Recommendations based 

on habitat monitoring 

framework

The habitat monitoring framework 

showed that, within the park and in 

general, Forest Habitats (Biodiversity 

and Ecosystem Pattern and Processes 

metrics) were assessed to be good, 

Wetland (Inland) Habitats were 

fair (Water Quality and Biodiversity 

metrics), and Artifi cial-terrestrial 

Habitats were degraded (Biodiversity, 

Ecosystem Pattern and Processes, and 

Air Quality). 

Forest Habitats (81%) have high 

overpopulation of deer, resulting 

in overgrazing of vegetation and 

limited regeneration of native 

seedlings as well as negative impacts 

upon diversity and abundance of 

forest interior dwelling bird species 

and increased road collisions. It is 

recommended to implement deer 

population control measures to 

reduce the current population, 26 

deer km-2. Another challenge to 

Forest Habitats was the presence of 

exotic plants (including shrubs and 

trees) currently over 16% by area. It 

LEFT: Mile-a-minute 

(Persicaria perfoliata), 

one of the fastgrowing, exotic 

plants the park works 

to control, reaches 

for the tree tops.

RIGHT: A volunteer 

holds an American 

robin (Turdus 

migratorius) as part 

of the joint National 

Park Service and the 

National Geographic 

Society’s May 2007 

BioBlitz, a ‘snapshot’ 

of biodiversity in 

Rock Creek Park.

Tom Paradis Ryan Valdez, DCNature.com

Tom Paradis

A white-tailed deer 

hesitates before 

crossing a winding, 

sometimes busy park 

road.
xv

EXECUTIVE SUMMARY

is recommended to emphasize early 

detection of these species, continue 

controlling them when detected and 

clearly prioritize control strategies 

based on characteristics such as 

relative invasion and expansion rates 

of different species. Forest Habitats 

within Rock Creek Park were 

found to be intact and to act as an 

important refuge for forest interior 

dwelling birds and potentially for 

other fauna such as amphibians. 

It is recommended to maintain 

forest connectivity and reduce 

forest fragmentation by minimizing 

stressors such as dumping, roads, 

structures, trails, and fi res.

Wetland Habitats (2%) within 

Rock Creek Park are challenged by 

elevated nutrient concentrations 

and salinity, resulting in negative 

impacts on stream fl ora and fauna 

and potential reduction of visitor 

experience. It is recommended that 

EXECUTIVE SUMMARY

road salting should be managed 

to further reduce impacts to 

streams and that nutrient reduction 

strategies should be implemented. 

Increased storm driven river fl ow 

and resultant bank erosion were also 

identifi ed as concerns.

Artifi cial-terrestrial Habitats (17%) 

within the park are a highly visible 

and highly utilized visitor use habitat 

but are poorly characterized in terms 

of ecosystem value. To improve 

future assessments and better 

identify management needs within 

this habitat, it is recommended to 

implement monitoring such as soil 

compaction and invasive exotic 

species presence in these areas, as 

well as develop inventories of some 

key insect species. The assessment 

of this habitat also highlighted the 

poor air quality and therefore the 

need for regional partnerships and 

education to improve air quality. 

Lisa Florkowski

A seasonal wetland, 

habitat to a variety 

of fl ora and fauna, 

begins to dry up in 

Rock Creek Park. 

With a summer 

picnic and soccer 

game, park visitors 

enjoy the artifi cialterrestrial habitat of 

mowed lawns within 

Rock Creek Park.

Lisa Florkowski
xvi

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Data gaps

Many aspects of park resources are 

well understood, however some data 

on important aspects of fl ora and 

fauna, as well as inputs and stressors, 

are still required. Data gaps and 

research needs identifi ed during the 

assessment include the quantifi cation 

of groundwater inputs and especially 

a better characterization of the 

water quality and biotic integrity of 

the many seeps and springs within 

the park. The sources of nutrients 

and salt are poorly defi ned (though 

clearly a challenge); tracer studies 

and identifi cation of point and 

diffuse sources both within and 

outside the park as well as the 

development of nutrient budgets 

would address this data gap. Other 

important areas for further indepth research include a better 

understanding of invasive exotic 

species and forest regeneration 

under high deer grazing pressure, 

especially the potential benefi ts 

of exclosures as well as a better 

understanding of potential barriers 

to plant and animal dispersal among 

forest patches as they become 

increasingly fragmented in the 

park and the park surroundings. 

An improved understanding of 

local air quality would be helpful 

to downscale regional data; park 

data could be used to calibrate air 

quality transport and depositional 

models to achieve this goal. Finally, 

another need is an accounting of 

inner-basin water transfers and 

coordination with regional agencies 

and stakeholders to maintain water 

quantity by reducing fl ows and 

reducing fl ow variability. 

Rock Creek Park staff 

and scientists review 

results of species 

survey.

NPS
xvii

NPS

Artifi cial-terrestrial 

habitats within 

Rock Creek Park 

can provide natural 

resources as well as 

recreational value.

Applicability of the 

natural resource condition 

assessment

The synthesis and frameworks 

presented in this report have 

the potential to include 

monitoring data directly in a park 

adaptive management cycle of 

conceptualization, implementation, 

evaluation, and communication. 

One of the challenges or data gaps 

that became apparent in the process 

of synthesizing available data was 

the disparity between the scales 

of available data and the scales of 

required management questions or 

needs. However, the identifi cation 

of relevant ecosystem metrics that 

are sensitive and measurable and the 

development of relevant threshold 

values mean that the presented 

synthetic frameworks (ecological 

monitoring-based and habitat-based) 

can be applied to the collection of 

monitoring data and answering 

specifi c within-park management 

questions.

Conclusions

Rock Creek Park was determined to 

have very high regional ecological 

value, supporting large intact 

areas of forest habitat, bird and 

amphibian communities, and 

increasingly rare seeps and springs. 

While the high deer population is 

the largest internal threat to the 

natural resource condition of the 

park, the impact of invasive exotic 

species and automobile traffi c are 

equally signifi cant. However, the 

natural resource value of Rock 

Creek Park is mainly threatened 

by regionally poor air quality and 

inadequate stormwater management 

in a highly developed urban and 

suburban watershed. This suggests 

that the strengthening of local and 

regional partnerships is essential if 

Rock Creek Park is to be maintained 

as an ecological oasis in an urban 

landscape. 

EXECUTIVE SUMMARY

EXECUTIVE SUMMARY
xviii

The Library of Congress

Built in the 1820s, Peirce Mill is the last extant 19th century gristmill in D.C.
1

NPS Archive

Chapter 1: Introduction

History of Rock Creek Park

Rock Creek Park was established in 

1890 as one of the fi rst federal parks. 

When the park was established, it 

was on the edge of a growing city 

and was already a favorite area for 

rural retreat in the nation’s capital. 

The park was established at a 

signifi cant time in the development 

of what would later become the 

National Park System (Mackintosh 

1985).1

 In 1872, Yellowstone was 

reserved as the fi rst national park by 

Congress, “dedicated and set apart 

as a public park or pleasure ground 

for the benefi t and enjoyment of the 

people.” This language is signifi cant 

because the legislation for Rock 

Creek Park adopted language from 

the Yellowstone Act. The protective 

prescription for Rock Creek, 

modifi ed only slightly from that of 

Yellowstone, called for regulations 

to “provide for the preservation 

from injury or spoliation of all 

timber, animals, or curiosities within 

said park, and their retention in 

their natural condition, as nearly as 

possible.” (Ch. 1001, 26 Stat 492). 

As the fi rst park situated in the 

nation’s capital, Rock Creek Park has 

a long and rich history. Peirce Mill 

is perhaps Rock Creek Park’s most 

prominent historic feature. Situated 

on the west bank of Rock Creek, 

Peirce Mill is the only one of several 

19th century mills still standing. The 

park commission acquired the mill 

property in 1892. The mill continued 

to grind corn and grain until 1897, 

when its main shaft broke. Today, the 

mill serves as a reminder of the park’s 

importance to local commerce and 

trade. 

Rock Creek Park would serve as a 

convenient and welcome respite for 

many prominent visitors, including 

U.S. Presidents. Best remembered 

among them is Theodore Roosevelt, 

who commented on the park in 

his 1913 autobiography (Roosevelt 

1913): 

“While in 

the White 

House, I always 

tried to get a 

couple hours’ 

exercise in the 

afternoons—

sometimes tennis, more often 

riding, or else a rough crosscountry walk, perhaps down 

Rock Creek ... Often, especially 

in the winters and early springs, 

we would arrange for a point to 

point walk, not turning aside for 

anything—for instance, swimming 

Rock Creek or even the Potomac 

if it came in our way. Of course 

under such circumstances we had 

to arrange that our return to 

Washington should be when it 

was dark, so that our appearance 

would scandalize no one. On 

several occasions we thus swam 

Rock Creek in the early spring 

when the ice was fl oating thick 

upon it. We liked Rock Creek for 

these walks because we could do 

so much scrambling and climbing 

along the cliffs.” 

Old wooden foot 

bridge, Rock Creek 

Park, Washington, 

D.C., ca. 1930.

1

 Several historical details used in this report about Rock Creek Park have been excerpted from the excellent 

administrative history written by an NPS employee, Barry Mackintosh, in 1985.

INTRODUCTION

A historical, political, and programmatic context to the Rock Creek natural resource 

condition assessment.
2

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

2

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Woodrow Wilson 

also enjoyed 

Rock Creek 

Park during 

his presidency, 

especially for 

walks while 

courting Edith 

Boiling Galt, who would become 

his second wife. The signifi cance 

of the park’s forest to Wilson is 

best evidenced by an event when 

the Offi ce of Public Buildings and 

Grounds undertook to remove 

numerous dead trees, mostly 

blighted chestnuts. Hundreds were 

sold to private cutters for telephone 

and telegraph poles. President 

Wilson was unconvinced that only 

blighted trees were removed and 

complained, 

“I do not profess to be a forester, 

but the great majority of trees 

that I have noticed laying prostrate 

in the park are certainly sound. 

I know a sound tree when I see 

it inside the bark. Moreover, in 

one part of the park a whole 

plantation of young pines have 

been cut down and it made my 

heart ache to see it.” 

The natural resources of Rock Creek 

Park have suffered from multiple 

environmental assaults since the 

park’s inception. Dr. E.P. Meinecke, a 

natural scientist on the National Park 

Service staff, recorded his views on 

Rock Creek Park in 1934:

“The strongest impression I get 

is that of disappointment. I have 

every reason to expect, in a large 

city, the capital of the Nation, a 

Park representing that which is 

best in American landscape art, 

designed to serve a large and 

growing number of its inhabitants 

as a place of recreation and refuge 

from the turmoil and heat of the 

city. I fi nd instead a curious mixture 

of more or less futile attempts at 

landscaping and of wild or rather 

unkempt growth, haphazardly 

developed, of amateurish attempts 

at embellishment side by side 

with crudest neglect ... There is 

at present, little pleasure to be 

gained from visiting the creek 

itself ... The water is dirty and the 

smell of decaying fi lth is anything 

but agreeable.” 

He attributed much of this problem 

to an inadequate storm sewer gate 

in Piney Branch, which in heavy rain 

let raw sewage into the stream. 

The primary feature of Rock Creek 

Park—the creek itself—would 

continually face assaults over time by 

its urban and suburban surroundings. 

In 1922, designated children’s 

bathing places were identifi ed 

as subject to very high fecal 

contamination, traced to sewage 

from Bethesda and Kensington, 

Maryland. Further, the volume of 

stream fl ow had become a matter of 

increasing concern in the 1920s. By 

1929, the U.S. Geological Survey and 

the Federal Water Pollution Control 

Administration had conducted 

detailed studies to monitor water 

quality in the creek. A stream gauge 

was installed and two reservoirs 

An August 1933 

hurricane caused 

extensive fl ooding 

and erosion to the 

streambeds of Rock 

Creek Park.

The Library of Congress
3

(Lakes Needwood and Frank) were 

built upstream in Montgomery 

County in the 1960s by the Soil 

Conservation Service (the gauge and 

reservoirs still exist). 

In summary, Rock Creek Park 

has served as a stalwart, though 

frequently beleaguered, jewel in the 

nation’s capital for 119 years. It is one 

of the largest natural urban parks 

in the world and faces immense 

challenges in providing recreational 

benefi ts to millions while striving to 

protect and preserve the ecological 

processes and natural resources of its 

streams and forests. 

Mission, goals, and context

There are two important 

mandates that broadly direct the 

natural resources protection and 

management of Rock Creek Park: 

the 1890 enabling legislation, and 

the National Park Service Organic 

Act of 1916 (“Organic Act”, Ch. 1, 39 

Stat 535). The “Organic Act,” which 

established the National Park Service 

(NPS), provides the primary mandate 

for natural resource protection 

within all national parks. It states,

“the Service thus established 

shall promote and regulate the 

use of Federal areas known as 

national parks, monuments and 

reservations ... by such means 

and measures as conform to 

the fundamental purpose of 

the said parks, monuments and 

reservations, which purpose is 

to conserve the scenery and the 

natural and historic objects and 

the wild life therein and to provide 

for the enjoyment of the same in 

such manner and by such means as 

will leave them unimpaired for the 

enjoyment of future generations.” 

Consequently, chief among Rock 

Creek Park’s environmental mandates 

is to preserve scenery and the natural 

and cultural resources of the park. 

Any visitor activities associated with 

enjoyment can occur only to the 

extent that they do not impair the 

scenery and the natural and cultural 

resources for future generations.

The General Management Plan for 

the park (NPS 2006), a guide and 

planning document that is subject to 

change and modifi cation, provides 

details of what resource conditions 

the park considers signifi cant 

and fundamental to the enabling 

legislation and management of 

the park. The NPS defi nes the most 

fundamental criteria for which the 

park is managed as follows:

● preserve the fl ow of water in Rock 

Creek;

● prevent the pollution of Rock 

Creek and the Potomac River; and

● preserve forests and natural 

scenery in and around 

Washington, D.C.

CHAPTER 1: INTRODUCTION

NPS

Transportation 

corridors, such as 

this Washington 

D.C. trolley bridge 

(ca. 1930) over 

Rock Creek, have 

challenged the park’s 

natural resources for 

many decades.

NPS

INTRODUCTION
4

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

4

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Natural resource condition 

assessment

In the 2003 Federal Appropriations 

Act, U.S. Congress instructed and 

funded NPS to assess environmental 

conditions in watersheds where 

National Park units are located. Park 

managers currently face threats 

from nutrient enrichment, exotic 

species, air and water pollution, 

stormwater, and urban development. 

The Watershed Condition Assessment 

(WCA) program was established to 

help NPS better address stressors 

and management issues at park, 

watershed, or regional scales. 

Chief among the goals of the 

WCA program is to disseminate 

information gained via Natural 

Resource Condition Assessments 

(NRCA) and to provide a basis for 

actions that reduce or prevent 

impairment of park resources.

The Natural Resource Condition 

Assessment proposed here will:

● use existing information sources 

to evaluate the condition of park 

natural resources;

● identify current or potential 

stressors to park natural resources; 

● identify information gaps or 

inventory and research needs; and

● provide data-based management 

recommendations. 

Information used in the assessment 

is multidisciplinary (e.g., biology, 

ecology, water chemistry, hydrology, 

etc.) and from a variety of sources, 

including NPS, other federal 

agencies, state and local agencies, 

organizations, and individual 

researchers. The NRCA is divided 

into three descriptive components: 

natural resources, current and 

The following signifi cant statements recognize the 

important features of the park:

● Rock Creek Park is one of the oldest and largest 

naturally managed urban parks in the United 

States.

● The park contains approximately 1,754 acres of 

valuable plant and wildlife habitat, providing 

protection for a variety of native species within a 

heavily urbanized area.

● Rock Creek Park encompasses a rugged stream 

valley of exceptional scenic beauty with forested, 

natural landscapes and intimate natural details, 

in contrast to the surrounding cityscape of 

Washington, D.C.

● Rock Creek Park’s forests and open spaces help 

defi ne the character of the nation’s capital. 

Rock Creek Park is therefore an urban park that has 

been established to preserve and maintain a natural 

environment within an urban landscape. The natural 

resources cited as fundamental or signifi cant are 

primarily forested and riparian habitats. Thus, we 

gave specifi c attention to these habitats during the 

condition assessment process.

The Library of Congress

Rock Creek Park has 

always provided 

recreational respite 

from city life, as 

illustrated by these 

picnickers, ca. 1940.
5

The Library of Congress

potential stressors, and a multi-scaled 

condition assessment. Practical limits 

to this assessment include a reliance 

on existing and readily usable data 

(i.e., no new data collection), and a 

park-wide scope to the assessment. 

Watershed-level interpretation was 

made whenever practical. However, 

such broad-scale inference was not 

always possible (or warranted) given 

the constraints described. 

The WCA program has adopted 

the goal of completing NRCAs for 

270 national parks by the end of 

fi scal year 2014. Rock Creek Park 

was selected as the fi rst pilot for a 

condition assessment in the National 

Capital Region in 2006. The timeline 

for the completion of all 11 natural 

resource parks in the National Capital 

Region is as follows: MONO, MANA, 

ANTI (2007-2010), PRWI, CATO, HAFE, 

upper CHOH (2009-2013), NACE, 

GWMP, WOTR, and lower CHOH 

(2011-2014).2

 The approximate level 

of funding per park is $44,000 and 

it is anticipated that NRCAs will be 

duplicated at each park on an eightyear continual rotation. 

Literature cited (Chapter 1)

Ch. 1001, 26 Stat 492. An act authorizing 

the establishing of a public park in the 

District of Columbia. 51st U.S. Congress, 

September 27, 1890.

Ch. 1, 39 Stat 535. Act to establish a 

National Park Service (Organic Act), 

1916. 16 USC 1, 2, 3, and 4. August 25, 

1916.

Mackintosh, B. 1985. Rock Creek Park: An 

administrative history. U.S. Department 

of Interior, National Park Service, 

Washington, D.C.

NPS. 2006. Draft general management 

plan/environmental impact statement: 

Rock Creek Park and the Rock Creek 

and Potomac Parkway. U.S. Department 

of Interior, Washington D.C.

Roosevelt, T. 1913. Theodore Roosevelt: 

an autobiography. MacMillan & Co., 

New York, NY.

2

 Park name acronyms are listed in Appendix Table B.6.

CHAPTER 1: INTRODUCTION

Historic Milkhouse 

Ford was one of at 

least a half-dozen 

natural creek 

crossings in the early 

1900s in Rock Creek 

Park.

INTRODUCTION
6

Aerial view shows the natural beauty of Rock Creek Park in fall colors.

Brain Gratwicke, DCNATURE.com
7

Rock Creek has generally high dissolved oxygen with reduction in summer months, and

an adequate acid neutralizing capacity and buffered stream waters . Shading keeps 

park waters cool year-round , and the logs , pools, and riffles of stream habitat 

maintain diverse amphibian communities. Abundant springs and seeps support 

significant and rare fauna .

Detail of Forest Habitat

Detail of Wetland Habitat

Rock Creek Park has high forest cover dominated by mixed beech-oak

forest with patches within and outside the park that can support sensitive 

forest-dwelling bird species .

Chapter 2: Natural Resources

Figure 2.1. 

Conceptual diagram 

illustrating the key 

natural resources 

of Rock Creek Park, 

Washington, D.C.

natural resources

A summary of key data available on the natural resource values within Rock Creek Park.
8

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

8

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Introduction

Rock Creek Park provides natural 

habitat for many plant and animal 

species as well as a recreational 

retreat for residents in the 

Washington D.C. area (Figure 

2.1). For more than a century, 

Washington, D.C. has grown to the 

point that the park no longer resides 

on the edge of the city, but within 

the city suburbs. The park maintains 

a wealth of natural resources that 

are enjoyed by millions of visitors 

each year. For the last 15 years, 

approximately 300,000 visitors per 

year have used the trails within 

Rock Creek Park for biking, hiking, 

jogging, or picnicking and around 

two million visitors per year have 

stayed within the park for at least 

half an hour (NPS Public Use Statistics 

Offi ce3

). 

Rock Creek Park, the NPS Center 

for Urban Ecology (CUE), National 

Capital Region Network, and the 

Maryland Biological Stream Survey. 

In addition, GIS data were obtained 

from federal, state, and local web 

portals, such as EPA STORET, USGS 

NWIS, USGS Seamless Server, and the 

USDA Geospatial Data Gateway. 

Initial scoping for legacy datasets was 

conducted during a meeting in June 

2006 at CUE. Attendees included 

scientists from NPS, local, and 

federal government, and academia 

(Appendix Table B.4).

Geology 

The Rock Creek watershed contains 

a geologic feature called the 

Fall Line, which marks the eastwest boundary between two 

physiographic provinces: the 

Piedmont and the Coastal Plain 

(Figure 2.2). The Piedmont Plateau 

underlies the western portion of 

the park and is characterized by 

exposed metamorphic rocks, rolling 

terrain, and fast fl owing streams. The 

Coastal Plain is fl atter, has few rocky 

outcrops, and has slower-moving 

streams (CH2m Hill 1979). 

Soils

The soils within Rock Creek Park 

refl ect, in part, the characteristics of 

the physiographic provinces running 

through the park (Figure 2.3). Soils 

found in the Piedmont Plateau 

areas (e.g., Brandywine Association) 

exhibit characteristics of moderate 

permeability, availability, and water 

holding capacity. These soils also 

tend to be moderately to severely 

erodible. Soils of the Coastal Plain 

(e.g., Sassafras-Chillum Association) 

contain relatively more gravel and 

sand, are well drained, and more 

acidic (CH2m Hill 1979). 

Data scoping 

workshop at the NPS 

Center for Urban 

Ecology.

IAN

3 http://www.nature.nps.gov/stats/

Data collection

Geospatial data (GIS) scoping began 

in September 2006 in conjunction 

with projects predating this effort 

(Dennison 2005). Data were 

exchanged and compiled through 

a series of meetings with staff from 
9

CHAPTER 2: NATURAL RESOURCES

natural resources

Figure 2.2. GIS 

data layer4 of 

geologic faults and 

bedrock geology 

for Rock Creek Park, 

Washington, D.C. 

4, 5 NCRN I&M

Figure 2.3. GIS data 

layer5

 of soil types 

found in Rock Creek 

Park, Washington, 

D.C.

N

2.0 km

Soil Types

ashe

beltsville

boune

brandywine

chillum

christiana

codorus

croom

glenlg

luka

joppa

keyport

manor

neshaminy

quarry

sassafras

sunnyside

udorthents

woodstown

DC boundary

2.0 km

N

geologic faults

Georgetown biotite tonalite

Georgetown biotite-hornblende 

tonalite

Georgetown garnetiferous

Georgetown quartz

granite

Kensington tonalite

Laurel formation

metavolcanic and meta-igneous 

rock

vein quartz

DC boundary

Geology

Piedmont

Coastal Plain

Physiographic provinces

MD

VA

WV

PA

DC DE

NC

NJ

F all Li ne
10

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

10

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Habitats

Using the International Union for the 

Conservation of Nature defi nitions6

(IUCN 2007), we considered three 

predominant ecological habitat types 

within Rock Creek Park. These were: 

Forest Habitat, Wetland (Inland) 

Habitat, and Artifi cial-terrestrial 

Habitat (Figure 2.4). These habitats 

are transitional between the two 

physiographic provinces represented 

within the park, as Rock Creek Park 

runs along the topographic break 

separating the Piedmont Plateau (to 

northwest of park) and the Atlantic 

Coastal Plain (to southeast of park) 

provinces. We recognize that many 

ecological classifi cation systems 

exist, many of which are based on 

vegetation communities (Anderson 

et al. 1998, Grossman et al. 1998) or 

land cover (Anderson et al. 1976). We 

chose a classifi cation system that is at 

a high level of classifi cation to permit 

comparisons to other systems (i.e., 

formation class or Anderson level 

one) while also being appropriate to 

data collection density.

Forest Habitat

Forest habitats constitute the 

majority of Rock Creek Park, covering 

approximately 81% of the park’s 

1,754 core acres (Figure 2.4), and 

are monitored at a series of sites 

(Figure 2.5). The park is dominated 

by a mixed beech (Fagus grandifolia) 

and oak (Quercus spp.) community 

(Figure 2.6). Though establishing 

legislation for the park identifi es 

“timber” as an essential resource 

to the park, NPS policies require 

consideration of a broader ecological 

context and therefore consider 

“timber” to mean not just individual 

trees, but the interrelated plant 

and animal populations that form 

the forest community as well (NPS 

2006). The forest at Rock Creek Park 

is comprised entirely of secondary 

growth, the majority of which is 

more than 100 years old. Activities 

prior to the park’s establishment 

in 1890, such as timber cutting, 

farming, and Civil War clearing, 

removed much of the original forest. 

A few large oaks still living in the 

Figure 2.4. GIS data 

layer7 of major 

habitat types in 

Rock Creek Park, 

Washington, D.C., 

as defi ned by 

aggregation of 

vegetation in Figure 

2.6. 

6 http://www.iucnredlist.org/static/major_habitats; Appendix Table B.1. 7

 NCRN I&M

2.0 km

N

Habitats

Forest (81%)

Wetland (Inland) (2%)

Artificial-terrestrial (17%)

DC boundary
11

Tom Paradis

Beech-white oak/

may apple forest 

association in Rock 

Creek Park.

Figure 2.5. Sampling 

sites8

 for fauna and 

forest vegetation 

within Rock Creek 

Park.

8

 Norris et al. 2007

natural resources

CHAPTER 2: NATURAL RESOURCES

2 km

N

ROCR-0186

ROCR-0010

ROCR-0092

ROCR-0172

ROCR-0094

VIRGINIA

MARYLAND

MARYLAND

forest monitoring locations

amphibian sampling sites

bird monitoring locations

deer counting routes

Rock Creek Park

DC boundary

I&M Forest Monitoring Sites
12

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

12

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

park have been estimated to be 

more than 280 years old and may be 

remnants of virgin growth. Today’s 

forests are primarily a mixture of 

deciduous species typical of the 

eastern deciduous forest in the later 

stages of succession. 

The dominant forest type within 

this region historically was a “mixed 

oak forest” (Monk et al. 1990). 

The composition of dominant 

species within this forest type has 

undoubtedly shifted since the 

nation’s capital was established. 

White oak (Quercus alba) has 

declined 12-49% in mid-Atlantic 

forests as a result of fi re suppression, 

land conversion, selective logging 

(Abrams 2003), and to some extent 

as a result of forest pests like gypsy 

moth. In northern Virginia, white 

oak has declined 19% in forest 

composition since pre-settlement 

(Orwig and Abrams 1994). White 

oak has been replaced by red maple 

(Acer rubrum) and red oak (Quercus 

rubra), which benefi tted from fi re 

suppression, chestnut blight, and 

logging of other species (Abrams 

2003). On a regional scale, fi re 

suppression has led to a cascade of 

changes in composition and structure 

of eastern forests. Grasslands, 

woodlands, and savannas have 

been replaced by closed-canopy, 

shade-tolerant, fi re-sensitive species 

(mesophytes) via a process called 

“mesophication” (Nowacki and 

Abrams 2008). The impacts of fi re 

suppression and mesophication 

will likely play a signifi cant role in 

shaping the long-term character of 

mesophytic forest communities of 

the mid-Atlantic region.

On a fi ner scale, the following 

fi ve forest associations have been 

identifi ed and mapped in Rock Creek 

Park using the National Vegetation 

Classifi cation System developed by 

The Nature Conservancy (Grossman 

et al. 1998). The beech-white 

oak/may apple forest association

occurs on moist to somewhat drier 

slopes. It is the most common of all 

associations found in the park. Two 

variants include the mixed oak/beech 

Figure 2.6. GIS 

data layer9 of 

predominant 

vegetation types for 

Rock Creek Park, 

Washington, D.C. 

9

 NCRN I&M

2.0 km

N

beech/mixed oak

beech/tulip poplar

beech/white oak

canopy gap

chestnut oak

loblolly pine/mixed oak

meadow

mowed lawn

shrub

sycamore/green ash

tulip poplar

Virginia pine/oak

DC boundary

Vegetation Types
13

CHAPTER 2: NATURAL RESOURCES

natural resources

Tom Paradis

Uninterrupted forest 

cover provides the 

shade needed for a 

wetland habitat in 

Rock Creek Park.

variant and the beech-tulip poplar 

variant. The tulip poplar forest 

association is uncommon and occurs 

on moist, mid-slope to low-slope 

sites that were cleared in the past. 

These sites are dominated by tulip 

poplar (Liriodendron tulipifera). The 

chestnut oak-black oak/huckleberry 

forest association is uncommon 

and occurs on ridge tops, convex 

upper slopes, and south-facing 

slopes on rocky, well-drained soils. 

The sycamore-green ash forest 

association is uncommon and occurs 

along stream banks, fl oodplains, 

and other low-lying areas subject to 

temporary or irregular fl ooding. The 

Virginia pine-oak forest association

is rare because it is an early to midsuccessional forest that is being 

replaced by hardwood forests. 

Remnants of this association occur on 

dry soils of hilltops in limited areas 

where forest succession has not yet 

replaced it.

Recent studies have been carried out 

to assess the habitat value of the 

forest within Rock Creek Park, as well 

as the surrounding area (Townsend 

et al. 2006). While there is high 

connectivity and low impervious 

surface within the park boundary, 

making this valuable habitat for fl ora 

and fauna, these features are more 

challenged when the park is placed 

in the context of the surrounding 

landscape (Figure 2.7).

five times area buffer

forest

non-forest

Rock Creek Park boundary

DC boundary

N

2.0 km

Figure 2.7. Extent of 

forest and non-forest 

landcover10 (Landsat 

30 m) within and 

around Rock Creek 

Park, Washington, 

D.C. for 2000.

Metric Inside Park Park + Buffer

Connectivity (m) 340 270

Impervious surface (%) 5 45

Dominant land cover 71 24

(% forest)

10 Townsend et al. 2006
14

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

14

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Rock Creek in late 

spring fl ow.

NPS

Wetland (Inland) Habitat

Wetland habitats, monitored at 

various stations (Figure 2.8) and 

which is primarily associated with 

the main Rock Creek and tributaries, 

makes up 2% of the 1,754 acres 

within the park (Figure 2.4). Rock 

Creek fl ows generally south for 

33 miles from its headwaters 

near Laytonsville, Maryland, to 

its confl uence with the Potomac 

River at Georgetown (Figure 2.9). 

Elevation at stream height falls from 

approximately 98 feet at the north 

end of the park to nearly sea level 

at the south end of the park (Figure 

2.10). 

The creek and tributaries support a 

diversity of fi sh species (at least 39 

species; Table 2.1). The waters within 

the parks, as determined by long-term 

monitoring stations (Figure 2.8), are 

of neutral pH (Figure 2.12), wellmixed (Figure 2.13), well buffered 

(Figure 2.14), and exhibit acceptable 

seasonal fl uctuations in temperature 

(Figure 2.15).

Another important component 

of wetland habitats are the 

approximately 40 seeps and springs 

throughout Rock Creek Park (Figure 

2.11). Several of the seep habitats 

are classifi ed as “hypotelminorheic,” 

meaning they share a unique set of 

physical and chemical characteristics 

and often provide subterranean 

habitat to rare species (Culver 

et al. 2006). For example, one 

species of the amphipod genus 

Stygobromus (Holsinger 1978) is 

federally endangered (S. hayi) and 

has extremely limited distributions. 

Another amphipod, Stygobromus 

kenki, is a candidate for similar 

federal protection (S. kenki is known 

from only a few sites—all within or 

near Rock Creek Park). 

RIGHT: Sampling for 

amphipods.

LEFT: Kenk’s 

amphipod (S. kenki)

is known to exist only 

within or near Rock 

Creek Park.

NPS NPS
15

CHAPTER 2: NATURAL RESOURCES

natural resources

Figure 2.9. GIS data 

layer12 depicting 

a portion of the 

stream network for 

Rock Creek Park, 

Washington, D.C. 

Upstream tributaries 

(Montgomery 

County, MD) are also 

shown. 

N

2.0 km

streams

Rock Creek Park

DC boundary

Streams

Figure 2.8. Stream 

sampling locations 

(n=10) used for 

long-term water 

quality monitoring11

at Rock Creek Park, 

Washington, D.C.

11, 12 NCRN I&M

2 km

N

SVPS

PYBR

PHBR

HACR

EGWA

BRBR

PYBR-LOG

PACR

VIRGINIA

MARYLAND

FEBR ROCR

LUBR

LRLR426

NCRW-304-N

LRLR425

ROCR: Rock Creek

FEBR: Fenwick Branch

NCRW-304-N 

PHBR: Pinehurst Branch

LUBR: Luzon Branch

BRBR: Broad Branch

PYBR: Piney Branch

HACR: Hazen Creek

EGWA: Edgewater Stables

SVPS: Soapstone Stream

PACR: Palisades Creek

Rock Creek and tributaries

Rock Creek Park watersheds

Rock Creek Park

DC boundary

I&M samples in Rock Creek:

Stream Sampling Sites

LRLR 425

LRLR 426

Montgomery County Dept. 

of Environ. Protection 

samples in Rock Creek: 
16

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

16

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Figure 2.10. GIS data 

layer13 of topographic 

elevation for 

Rock Creek Park, 

Washington, D.C.

13, 14 NCRN I&M

Figure 2.11. GIS data 

layer14 depicting the 

location of springs, 

seeps, and pools 

(n=15) in Rock Creek 

Park, Washington, 

D.C.

2.0 km

10 - 150 ft

150 - 300 ft

300 - 450 ft

>450 ft

DC boundary

Elevations

N

N

2.0 km

springs, seeps, & pools

Rock Creek Park

DC boundary

Springs, Seeps, & Pools
17

CHAPTER 2: NATURAL RESOURCES

natural resources

Common Name Species 2002 2003 2004 2005 Total

Alewife Alosa pseudoharengus 379 472 361 287 1499

Longnose Dace Rhinichthys cataractae 54 34 188 763 1039

Spottail Shiner Notropis hudsonius 262 95 361 279 997

White Sucker Catostomus commersoni 296 159 229 303 987

Bluegill Lepomis macrochirus 162 134 101 153 550

Blacknose Dace Rhinichthys atratulus 56 38 66 256 416

Tessellated Darter Etheostoma olmstedi 83 54 111 168 416

Pumpkinseed Lepomis gibbosus 202 23 54 125 404

Swallowtail Minnow Notropis procne 38 92 120 107 357

Bluntnose Minnow Pimephales notatus 53 53 55 150 311

American Eel Anguilla rostrata 31 49 84 84 248

Spotfi n Shiner Cyprinella spiloptera 53 49 50 26 178

Yellow Bullhead Ameiurus natalis 34 37 32 61 164

Largemouth Bass Micropterus salmoides 26 90 20 11 147

Fallfi sh Semotilus corporalis 51 17 30 19 117

Channel Catfi sh Ictalurus punctatus 4 39 32 11 86

Redbreast Sunfi sh Lepomis auritus 21 11 12 6 50

Carp Cyprinus carpio 26 17 2 1 46

Cutlips Minnow Exoglossum maxillingua 6 3 9 19 37

Golden Redhorse Moxostoma erythrurum 2 1 17 9 29

Hickory Shad Alosa mediocris 22 22

Smallmouth Bass Micropterus dolomieu 5 1 2 11 19

Creek Chubsucker Semotilus atromaculatus 8 3 4 1 16

Green Sunfi sh Lepomis cyanellus 1 4 4 7 16

Brown Bullhead Ameiurus nebulosus 3 2 7 12

Eastern Silvery Minnow Hybognathus regius 12 12

Sea Lamprey Petromyzon marinus 1 1 4 5 11

Goldfi sh Carassius auratus 23 49

Greensided Darter Etheostoma blennioides 2 169

Gizzard Shad Dorosoma cepedianum 5 5

Central Stoneroller Campostoma anomalum 4 4

Golden Shiner Moxostoma erythrurum 2 24

Redear Sunfi sh Lepomis microlophus 2 2

Black Crappie Anguilla rostrata 112

Musky Esox masquinongy 1 1

Quillback Carpsucker Carpiodes cyprinus 1 1

Striped Bass Morone saxatilis 1 1

White Perch Morone americana 1 1

Yellow Perch Perca fl avescens 1 1

Total 1858 1486 1982 2900 8226

Table 2.1. Fish species and number of individuals captured during annual park surveys (2002-2005).
18

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

18

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

6.0

5.0

9.0

8.0

7.0

date

pH

threshold range 6.0  pH 

Feb 05 May 05 Sep 05 Dec 05 Mar 06 Jul 06 Oct 06 Jan 07 Apr 07 Aug 07 Nov 07 Feb 08

2

Feb 05 May 05 Sep 05 Dec 05 Mar 06 Jul 06 Oct 06 Jan 07 Apr 07 Aug 07 Nov 07 Feb 08

0

16

14

12

4

8

6

10

date

dissolved oxygen (mg L-1)

 Jun 1-Jan 31 threshold 3.2 mg L-1

 Feb 1-May 31 threshold 5.0 mg L-1

Feb 05 May 05 Sep 05 Dec 05 Mar 06 Jul 06 Oct 06 Jan 07 Apr 07 Aug 07 Nov 07 Feb 08

date

1000

0

2500

1500

500

2000

3500

3000

Acid Neutralizing Capacity 

(μequiv L-1 CaCO3

)

 threshold 200 μequiv L-1 CaCO3

5

0

35

30

10

20

15

25

date

water temperature (oC)

threshold

32.2 oC

Feb 05 May 05 Sep 05 Dec 05 Mar 06 Jul 06 Oct 06 Jan 07 Apr 07 Aug 07 Nov 07 Feb 08

Figure 2.12. Median, 

minimum, and 

maximum monthly 

pH values15 for 10 

stream sampling 

locations (see Figure 

2.8) from 2005-2007 

for Rock Creek Park. 

Acceptable ranges 

(6.0  pH  8.5) are 

shown.

Figure 2.13. Median, 

minimum, and 

maximum monthly 

dissolved oxygen 

concentration (mg 

L-1) for 10 stream 

sampling locations16

(see Figure 2.8) 

from 2005-2007 for 

Rock Creek Park. 

Acceptable ranges 

(DO  3.2 mg L-1 from 

Jan-Jun, DO  5.0 

mg·L-1 from FebMay) are shown.

Figure 2.14. Median, 

minimum, and 

maximum monthly 

acid neutralizing 

capacity (ANC; mg 

CaCO3

 L-1) for 10 

stream sampling 

locations17 (see Figure 

2.8) from 2005-2007 

for Rock Creek Park. 

Acceptable range 

(mg CaCO3

 L-1  10 

mg L-1) is shown.

Figure 2.15. Median, 

minimum, and 

maximum monthly 

water temperature 

(°C) for 10 stream 

sampling locations18

(see Figure 2.8) 

from 2005-2007 for 

Rock Creek Park. 

Acceptable range 

(temp.  32.2°C) is 

shown.

15, 16, 17, 18 Norris et al. 2007
19

CHAPTER 2: NATURAL RESOURCES

natural resources

Artifi cial-terrestrial Habitat

The artifi cial-terrestrial habitats, 

which make up 17% of Rock Creek 

Park (Figure 2.4), include managed 

meadows, community gardens, and 

lawns. One of the largest habitat 

areas is the golf course in the 

Chadwick Cipiti, DCNature.com

central eastern section of the main 

body of the park along Rock Creek 

itself. These artifi cially created or 

maintained habitats are important 

resources for recreation while also 

providing dispersal and stopover 

habitat for animals and insects 

(Angold et al. 2006, Snep et al. 2006). 

Lisa Florkowski

While the natural 

resources of Meridian 

Hill Park are not 

included in this 

particular condition 

assessment, the park 

is a component of 

Rock Creek Park and 

is a good example of 

an artifi cially created 

landscape with its 

many fountains, 

statues, and gardens.

Rock Creek Park has 

many picnic areas 

and recreational 

lawns.
20

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

20

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Literature cited (Chapter 2)

Abrams, M.D. 2003. Where has all 

the white oak gone? BioScience 

53(10):927-939.

Anderson, J.R., E.E. Hardy, J.T. Roach, and 

R.E. Witmer. 1976. A Land Use and Land 

Cover Classifi cation System for Use with 

Remote Sensor Data. U.S. Geological 

Survey Professional Paper 964, Reston, 

VA: U.S. Geological Survey.

Anderson, M., P. Bourgeron, M.T. Bryer, 

R. Crawford, L. Engelking, D. FaberLangendoen, M. Gallyoun, K. Goodin, 

D.H. Grossman, S. Landaal, K. Metzler, 

K.D. Patterson, M. Pyne, M. Reid, L. 

Sneddon, and A.S. Weakley. 1998. 

International classifi cation of ecological 

communities: Terrestrial vegetation 

of the United States. Volume II. The 

National Vegetation Classifi cation 

System: List of types. The Nature 

Conservancy, Arlington, VA.

Angold, P.G., J.P. Sadler, M.O. Hill, A. 

Pullin, S. Rushton, K. Austin, E. Small, 

B. Wood, R. Wadsworth, R. Sanderson, 

and K. Thompson. 2006. Biodiversity in 

urban habitat patches. Science of the 

Total Environment 360:196-204.

CH2m Hill, 1979. Rock Creek Watershed 

Conservation Study, prepared for 

the National Park Service. CH2M Hill. 

W12124.A0.

Culver, D.C., T. Pipan, and S. Gottstein. 

2006. Hypotelminorheic—a unique 

freshwater habitat. Subterranean 

Biology 4:1-7. 

Dennison, W. 2005. Providing tools to 

facilitate syntheses and assessments of 

National Parks of the National Capital 

Region. NPS Cooperative Agreement 

#1443CA309701200, Task # J3992-05-

0105, Mod. #06-0001.

Grossman, D.H., D. Faber-Langendoen, 

A.S. Weakley, M. Anderson, P. 

Bourgeron, R. Crawford, K. Goodin, S. 

Landaal, K. Metzler, K.D. Patterson, M. 

Pyne, M. Reid, and L. Sneddon. 1998. 

International classifi cation of ecological 

communities: Terrestrial vegetation 

of the United States. Volume I. The 

National Vegetation Classifi cation 

System: development, status, and 

applications. The Nature Conservancy, 

Arlington, VA.

Holsinger, J.R. 1978. Systematics of 

the subterranean amphipod genus 

Stygobromus (Crangonyctidae), part II: 

Species of the eastern United States. 

Smithsonian Contributions to Zoology, 

Number 266.

IUCN. 2007. Habitats classifi cation 

scheme (version 3.0). International 

Union for the Conservation of Nature. 

http://www.iucnredlist.org/static/

major_habitats.

Monk, C.D., D.W. Imm, and R.L. Potter. 

1990. Oak forests of eastern North 

America. Castanea 55(2):77-96.

NPS. 2006. Draft general management 

plan/environmental impact statement: 

Rock Creek Park and the Rock Creek 

and Potomac Parkway. U.S. Department 

of Interior, Washington D.C.

Norris, M., J.P. Schmit, and J. Pieper. 2007. 

National Capital Region Network 

2005-2006 Water Resources Monitoring 

Report. Natural Resource Program 

Center, Fort Collins, CO. NPS/NCRN/

NRTR - 2007/066.

Nowacki, G.J. and M.D. Abrams. 2008. The 

demise of fi re and “mesophication” 

of forests in the eastern United States. 

BioScience 58(2):123-138.

Orwig, D.A. and M.D. Abrams. 1994. 

Land-use history (1720-1992), 

composition, and dynamics of oak-
21

CHAPTER 2: NATURAL RESOURCES

natural resources

pine forests within the Piedmont and 

Coastal Plain of northern Virginia. 

Canadian Journal of Forest Research 

24:1216-1225.

Snep, R.P.H., P.F.M. Opdam, J.M. Baveco, 

M.F. WallisDeVries, W. Timmermans, 

R.G.M. Kwak, and V. Kuypers. 2006. 

How peri-urban areas can strengthen 

animal populations within cities: 

A modeling approach. Biological 

Conservation 127:345-355. 

Townsend, P.A., R.H. Gardner, T.R. 

Lookingbill, and C.C. Kingdon. 2006. 

Remote sensing and landscape pattern 

protocols for long-term monitoring of 

parks in the National Capital Region. 

Draft Protocols Report. University of 

Maryland Center for Environmental 

Science, Appalachian Laboratory, 

Frostburg, MD.
22

Invasive exotic English ivy (Hedera helix) overtakes tree.

Jane Thomas, IAN
23

Urban impervious surfaces surrounding Rock Creek Park deliver road salt , 

nutrients , and toxicants into park waterways, impacting water quality, 

and threatening fish and invertebrates . Storm events can deliver high 

water volumes to Rock Creek, disrupting stream flows and habitats. Atmospheric 

pollution can result in acid rain and deposition into the park waterways, 

increasing mercury in fish tissue and posing a potential human health risk . 

Leaking sewer lines crossing the park and pet feces raise nutrient levels 

in streams , and lead to eutrophication and a decline in fish health.

TP

$ $ MUI EM PR

$ $ MUI ME PR

Dense urban development surrounding Rock Creek Park brings intense visitor use 

of trails which can introduce invasive plant species , and trash dumping . 

High ozone levels during summer can cause potential human health issues and 

damage plants and trees . Deer overpopulation reduces seedling survival 

and is a hazard to vehicles on the roads within and outside the park.

3

 

3

Stressors to Forest Habitat

$ $

M PREMIU

$ $

PREMIUM

TP

Stressors to Wetland Habitat

Chapter 3: Current & Potential Stressors

A summary of key data available on the current and potential stressors of natural 

resources within Rock Creek Park.

Figure 3.1. 

Conceptual diagram 

illustrating the 

major environmental 

stressors facing 

Rock Creek Park, 

Washington, D.C.

STRESSORS
24

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

24

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Introduction

Rock Creek Park is a green island 

in a sea of pavement. Dense urban 

development surrounds the park, 

bringing with it intense trail use, 

dumping, and continual introduction 

of invasive exotic species (Figure 3.1). 

Additionally, the park encompasses 

the bottom nine miles of the Rock 

Creek watershed, making the creek 

IAN

BELOW: Stormwater 

originating in the 

park’s watershed 

delivers sediment 

and toxicants that 

impact water quality 

downstream in Rock 

Creek Park.

LEFT and RIGHT: 

Surrounded by 

houses, businesses, 

and roads, the 

dumping of trash and 

debris in Rock Creek 

Park is an on-going 

challenge.

NPS IAN

susceptible to degradations in 

water quality and increases in storm 

fl ows that are beyond management 

control. Of the 266,162 acre Rock 

Creek watershed, just 9,536 acres 

(3.6%) are managed by the National 

Park Service. Consequently, Rock 

Creek Park faces challenges in 

maintaining ecological integrity 

within a heavily urbanized landscape.
25

CHAPTER 3: CURRENT & POTENTIAL STRESSORS

Air quality

Stressors to air quality are additional 

external factors in an urbanized 

landscape. Data from surrounding 

ambient air quality stations (Figure 

3.2) portray excessive ozone levels 

(Figure 3.3) and large amounts of 

wet deposition of nitrate (Figure 

3.4), sulfate (Figure 3.5), and mercury 

(Figure 3.6). Regionally, atmospheric 

deposition of sulfate (Figure 

3.7) and mercury (Figure 3.8) are 

persistent problems. As in the case of 

upstream pollution in park waters, 

these atmospheric stressors act to 

potentially degrade the resources 

in Rock Creek Park, yet stressor 

abatement outside the park poses 

signifi cant challenges.

A coal-fi red power 

plant (foreground) 

in Washington, D.C., 

emits particulate 

(soot) pollution 

to surrounding 

neighborhoods.

Gristmill.grist.org

Figure 3.2. Map of 

sampling stations19

used for measuring 

ambient air quality 

near Rock Creek Park, 

Washington, D.C.

19 Data sources: National Atmospheric Deposition Program http://nadp.sws.uiuc.edu/; Mercury Deposition Network 

http://nadp.sws.uiuc.edu/mdn/.

STRESSORS

#

$

%

§ ̈¦495

§ ̈¦395

§ ̈¦295

§ ̈¦295

§ ̈¦270

"

"

ANNE

ARUNDEL

PRINCE GEORGE’S

5 km

N

110010041

110010042

BEL216/MD99

MONTGOMERY

ARLINGTON

ALEXANDRIA

FAIRFAX

DISTRICT OF COLUMBIA

Air Sampling Stations

%

#

$

"

NADP / MDN / CastNet

ozone

ozone / visibility

visibility

state / county boundaries

Rock Creek Park

McMillan

110010043

Takoma

110010025
26

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

26

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Figure 3.3. Hourly 

atmospheric ozone 

concentration (8-hr 

mean ppm) from 

1994-2003 at the 

southeast end of 

McMillan Reservoir20

(see Figure 3.2), 

Washington, D.C. 

Acceptable range 

(8-hr mean  0.075 

ppm) is shown.

20 Environmental Protection Agency; NPS Air Resources Division; http://www.epa.gov/castnet/ 21 National Atmospheric Deposition Program; http://nadp.sws.uiuc.edu/

threshold

0.075 ppm

1994 1996 1998 1999 2001 2003

0.00

0.12

0.04

year

1995 1997 2000 2002

ozone ppm (3-year mean) 0.08

Site 25

Site 43

Site MD99

Site MD03

Site VA10

5

1984 1986 1985

0

20

25

15

10

year

wet NO3 deposition (kg ha-1 yr-1)

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

 forest threshold 15 kg ha-1 yr-1

 other habitats threshold 10 kg ha-1 yr-1

Figure 3.4. Annual 

wet nitrate 

deposition21 (mg L-1) 

from 1984-2007 for 

sites MD99, MD03, 

and VA10 (see Figure 

3.2). Acceptable 

ranges for forest 

(NO3

-  15 kg ha-1

yr-1) and cultivated 

(NO3

-  15 kg ha-1 yr-1) 

habitats are shown.
27

Site MD99

Site MD03

Site VA10

5

1984 1986 1985

0

25

20

30

35

15

10

year

wet SO4 deposition (kg ha-1 yr-1)

1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

 threshold 10 kg ha-1 yr-1

2003 2004 2005 2006 2007

year

threshold 2 ng L-1

20

0

120

100

60

80

40

Hg concentration (ng L-1)

Figure 3.5. Mean 

annual wet sulfate 

deposition22 (mg L-1) 

from 1984-2007 for 

sites MD99, MD03, 

and VA10 (see Figure 

3.2), Washington, 

D.C. Acceptable 

range (SO4

-2  18 kg 

ha-1 yr-1) is shown. 

Figure 3.6. Mean 

monthly mercury 

(Hg) concentration 

(ng L-1) at Beltsville 

Agricultural Research 

Center23 (see Figure 

3.2) in Beltsville, MD. 

Acceptable range (Hg 

 2 ng L-1) is shown.

Figure 3.7. Total 

wet sulfate (SO4

-2) 

deposition (kg ha-1) 

for the continental 

United States in 2006. 

STRESSORS

22 National Atmospheric Deposition Program; http://nadp.sws.uiuc.edu/ 23 Mercury Deposition Network; http://nadp.sws.uiuc.edu/mdn

CHAPTER 3: CURRENT & POTENTIAL STRESSORS
28

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

28

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

The park is impacted heavily by the 

surrounding urban environment. It is 

positioned in the lower-most part of 

the watershed, making it vulnerable 

to upstream impacts. Air monitoring 

data (Figure 3.2) for visibility show 

a moderate amount of airborne 

particulate matter (soot; Figure 3.9). 

Surrounding land development has 

removed forest cover and isolated 

park habitats (Figure 2.7). Upstream 

development and increased 

imperviousness within the watershed 

appear also to be increasing the 

rise rate (i.e., “fl ashiness”) of Rock 

Creek (Figure 3.10). A more detailed 

analysis of extra-park infl uences 

on natural resources is provided in 

Chapter 5.

Downtown 

Washington, D.C. 

area in: (TOP) 

October 2005 where 

the visual range 

was 55 miles, and, 

(BOTTOM) July 2006 

where the visual 

range was 25 miles. 

Source: http://www.

nature.nps.gov/air/

WebCams/parks/

nacccam/washcam.

cfm.

Figure 3.8. Total 

wet mercury (Hg) 

deposition (μg m-2) 

for the continental 

United States in 2006.

NPS

NPS
29

threshold

15 mg m-3

Site 41

Site 42

Site 43

5

1999 2000 2001 2002 2003 2004

0

20

15

10

year

PM2.5 (mg m-3)

Figure 3.9. Mean 

monthly particulate 

matter (soot; PM2.5) 

concentration with 

standard deviation 

for sites 41, 42, and 

4324 from 1999-2004 

(listed as 1100100xx 

Figure 3.2). Sampling 

intensity increased 

after 2003. 

24 Interagency Monitoring of Protected Visual Environments http://vista.cira.colostate.edu/improve/ 25 NCRN I&M

Lake Needwood is a 

75-acre reservoir that 

is located on Rock 

Creek in Rock Creek 

Regional Park in 

Montgomery County 

near Rockville, 

Maryland. The 

man-made lake was 

created to provide 

fl ood control. It also 

protects the water 

quality of the creek 

by functioning as a 

retention basin to 

trap sediment from 

stormwater runoff.

Wikimedia Commons

5

1930 1939 1934

0

20

25

15

10

40

35

30

55

50

45

60

year

rate (cfs/day)

1944 1949 1954 1959 1964 1969 1974 1979 1984 1989 1994 1999 2004

pre-impact flows (1930-1967)

post-impact flows (1968-2007)

75th percentile

median

25th percentile

1930-1967 and 1968-2007 Rise Rate Figure 3.10. 

Comparisons in rise 

rate (cfs day-1)

between time period 

prior to (1930-

1967) and after 

(1968-2007) Lake 

Needwood reservoir 

construction. Data 

from USGS level 

logger at Sherrill 

Drive25 in Rock Creek 

Park, Washington 

D.C. 

STRESSORS

CHAPTER 3: CURRENT & POTENTIAL STRESSORS
30

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

30

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Water quality

External stressors

Urban development has resulted in 

a dense grid of sewer lines, some of 

which run through the park (Figure 

3.11). As a result, the park has over 

217 combined sewer outfalls or 

stormwater drains that empty into 

Rock Creek (Figure 3.12). Hazardous 

materials also surround the park. 

Approximately 222 sites containing 

hazardous materials (e.g., fuel tanks) 

are located within 2 km of a park 

unit (Figure 3.13).

Figure 3.11. GIS data 

layer26 of a portion of 

the Washington, D.C. 

sewer system.

26, 27 NCRN I&M

sewers

streams

Rock Creek Park

DC boundary

Sewer System

N

2.0 km

Figure 3.12. GIS 

data layer27 of 

point source 

inputs (combined 

sewer outfalls and 

stormwater drains) 

to Rock Creek 

Park, Washington, 

D.C. Two hundred 

seventeen sources 

are shown in this 

geographic extent. 

A total of 342 

are located in or 

adjoining the entire 

park unit. 

N

2.0 km

discharge locations

streams

Rock Creek Park

DC boundary

Point Source Threats
31

TOP: This combined 

sewer outfall is slated 

to be modifi ed to 

divert sewage to a 

treatment plant.

LEFT: Combined 

sewer outfalls can 

cause high bacteria 

levels in Rock Creek.

Tom Paradis

CHAPTER 3: CURRENT & POTENTIAL STRESSORS

STRESSORS

28 NCRN I&M

Figure 3.13. GIS 

data layer28 showing 

222 sites in and 

around Rock Creek 

Park, Washington, 

D.C. that contain 

hazardous materials.

Hazardous Materials

Locations

hazmat sites

streams

Rock Creek Park

DC boundary

N

2.0 km

Tom Paradis
32

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

32

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Within park evidence

Data from ten stream monitoring 

sites in Rock Creek Park (Figure 

2.8) characterize the type of 

stressors facing riparian fauna 

and fl ora. Stream salinity (Figure 

3.14) was high when compared to 

acceptable concentrations. Nitrate 

concentrations fl uctuate considerably 

according to park location (Figure 

3.15). Total phosphorus was found at 

very high concentrations, orders of 

magnitude above acceptable levels 

(Figure 3.16).

0.0

2.5

2.0

0.5

1.5

1.0

date

salinity

threshold

< 0.25

Feb 05 May 05 Sep 05 Dec 05 Mar 06 Jul 06 Oct 06 Jan 07 Apr 07 Aug 07 Nov 07 Feb 08

6

0

12

14

8

2

4

10

date

NO3 (mg L-1)

threshold

< 2 mgL-1

Feb 05 May 05 Sep 05 Dec 05 Mar 06 Jul 06 Oct 06 Jan 07 Apr 07 Aug 07 Nov 07 Feb 08

0

9000

2000

1000

3000

5000

4000

6000

8000

7000

date

total phosphorus (μg L-1)

Feb 05 May 05 Sep 05 Dec 05 Mar 06 Jul 06 Oct 06 Jan 07 Apr 07 Aug 07 Nov 07 Feb 08

threshold

< 36.56 μgL-1

Figure 3.14. Median, 

maximum, and 

minimum monthly 

salinity concentration 

for 10 stream 

sampling locations29

(see Figure 2.8) 

from 2005-2007 for 

Rock Creek Park, 

Washington, D.C. 

Acceptable range 

(salinity < 0.25) is 

shown. 

Figure 3.15. Median, 

maximum, and 

minimum monthly 

nitrate (NO3

-

) 

concentration (mg 

L-1) for 10 stream 

sampling locations30

(see Figure 2.8) 

from 2005-2007 for 

Rock Creek Park, 

Washington, D.C. 

Acceptable range 

(NO3

-  2.0 mg L-1) is 

shown.

Figure 3.16. Median, 

maximum, and 

minimum monthly 

organic total 

phosphorus (TP) 

concentration (μg 

L-1) for 10 stream 

sampling locations31

(see Figure 2.8) 

from 2005-2007 for 

Rock Creek Park, 

Washington, D.C. 

Acceptable range (P 

37 μg L-1) is shown.

29, 30, 31 Norris et al. 2007
33

CHAPTER 3: CURRENT & POTENTIAL STRESSORS

STRESSORS

Surrounding landscape

Scoping for GIS data was 

accomplished via a series of meetings 

with staff from Rock Creek Park, 

the Center for Urban Ecology (CUE), 

National Capital Region Network 

(NCRN), and the Maryland Biological 

Stream Survey. In addition, GIS data 

were obtained from federal, state, 

and local web portals, such as EPA 

STORET, USGS NWIS, USGS Seamless 

Server, and the USDA Geospatial 

Data Gateway. Three additional 

synthetic GIS layers (population, 

roads, and impervious surface) were 

generated.

N

2.0 km

trails

Rock Creek Park

DC boundary

Park Trails Figure 3.17. GIS 

data layer32 showing 

the trail system of 

Rock Creek Park, 

Washington, D.C.

32 NCRN I&M

Visitors enjoy the 

many trails of Rock 

Creek Park. 

Lisa Florkowski

Watershed

Although Rock Creek Park is 

81% forested (accessible through 

multiple trails; Figure 3.17), the 

entire watershed contains just 24% 

forest and is one of the most rapidly 

growing urban areas within the 

United States. 

Lisa Florkowski
34

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

34

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Population

The population layer was derived 

using the Year 2000 Census block 

information. In ArcGIS 9.2, the base 

watershed layer was used to clip 

census blocks to the watershed 

boundaries. Using the ArcGIS fi eld 

calculator, area was calculated for 

each of the census blocks and then 

for each of the clipped blocks. A ratio 

was calculated by taking the area of 

the clipped block compared to the 

area of the original block. The ratio 

and the population for the block were 

then multiplied to give a population 

for each clipped block. These clipped 

block populations were then summed 

within each sub-watershed to give a 

total population. 

For this technique, the population 

was assumed to be evenly distributed 

throughout each census block. Census 

blocks are the smallest unit for 

which the Census Bureau maintains 

information. By using these units, the 

error associated with assuming evenly 

distributed population was minimized. 

There was a large range of 

population values for each 

watershed. To facilitate comparison 

between watersheds, population was 

normalized to watershed area. Using 

the ArcGIS fi eld calculator, the area 

was calculated for each watershed. 

The area of the park was removed 

from each watershed area to give 

an accurate population density. 

Since there are no people living in 

the park, population density was 

calculated using the area of each 

watershed outside the park rather 

than the total area of the watershed. 

These normalized population values 

are shown in the map (Figure 3.18). 

There is no population threshold and 

therefore the color breaks are based 

on quantities.

Roads

Roads have a signifi cant effect on 

wildlife and habitat quality, and 

this effect contributes to ecosystem 

disruption and degradation 

(Bechtold et al. 1996). Roads 

affect wildlife directly through 

vehicle-animal collisions and noise 

pollution, and indirectly through 

increased runoff, erosion, sediment 

loading causing fi sh kills, decreased 

dissolved oxygen concentrations, 

increased temperature, and impaired 

habitat. Roads also lead to forest 

fragmentation, increased edge 

habitat and increased invasive exotic 

plants (Bechtold et al. 1996). Haynes 

et al. (1996) suggest road density 

classifi cations based on the spawning 

habitat of salmon. A road density of 

0.02-0.1 miles per square mile (mi mi-2) 

are considered very low; 0.1-0.7 mi 

mi-2 is considered low; 0.7-1.7 mi mi-2

is considered moderate; 1.7-4.7 mi mi-2

is considered high; and greater than 

4.7 mi mi-2 is considered extremely 

high. Bechtold et al. (1996) similarly 

categorized road density into fi ve 

classifi cations for an analysis of grizzly 

Figure 3.18. 

Population map 

derived from U.S. 

Census Bureau33 block 

population estimates. 

Blocks were clipped 

to the subwatershed 

boundary and the 

total population was 

estimated for each 

subwatershed.

2 km

N

0 - 375

376 - 625

626 - 1000

1001 - 3500

>3500

People per sq km

Population

33 NCRN I&M
35 34 NCRN I&M

CHAPTER 3: CURRENT & POTENTIAL STRESSORS

STRESSORS

2 km

N

0 - 1.5

1.6 - 3.1

3.2 - 6.2

6.3 - 12.5

> 12.5

Roads (km km-2)

Road Density

by Watershed

Figure 3.19. Road 

density34 was 

calculated by 

measuring the length 

of the roads within 

the subwatershed 

boundary. The length 

was then divided by 

the subwatershed 

area to produce 

density.

bear habitat. Their classifi cations 

were 0-0.5 mi mi-2, 0.5-1.0 mi mi-2, 

1.0-2.0 mi mi-2, 2.0-5.0 mi mi-2, and 

> 5.0 mi mi-2. Both classifi cations 

were similar, suggesting that these 

road densities are appropriate for a 

variety of species. 

Multiple derived road layers were 

calculated from the same base map. 

The fi rst was road density (Figure 

3.19). This layer was calculated using 

the p. 32/104—TIGER/Line® Files 

(Census Bureau 2000). These line 

fi les were clipped to the watershed 

boundary layer and the park 

boundary layer. The length of the 

roads was then calculated using the 

ArcGIS spatial calculator. Using the 

watershed area previously calculated, 

road length was normalized to 

watershed area. The road densities 

found in Rock Creek watershed were 

much higher than the road densities 

found in Bechtold et al. (1996) and 

Haynes et al. (1996). There are only 

three watersheds that have a road 

density less than 5 mi mi-2. In order to 

show some variation in the map, the 

classifi cation scheme condenses the 

Wildlife are often 

casualties on the 

many busy roads 

that cross Rock Creek 

Park.

Tom Paradis

literature values into two colors and 

splits the remaining colors based on 

the range of road densities found in 

the watershed.
36

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

36

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

The second road density map 

(Figure 3.20) is a comparison of road 

density and stream density. Stream 

density was calculated using the 

same method used for road density. 

35 NCRN I&M

2 km

N

>1.00

0.61 - 1.00

0.41 - 0.60

0.21 - 0.40

0.00 - 0.20

Stream to Road

Density Ratio

by Watershed

Figure 3.20. Stream 

density35 was 

calculated using the 

same method used 

for road density. 

The ratio of road to 

stream density was 

then calculated.

Milkhouse Ford, 

where a municipal 

road merges with 

Rock Creek.

Lisa Florkowski

The stream density was calculated 

from the high resolution National 

Hydrography Dataset stream layer. 

This stream layer was chosen over 

the layer created from the Digital 

Elevation Model (Figure 2.10) 

because the National Hydrography 

Dataset stream layer more accurately 

depicts the streams. It has been 

suggested that when road density 

approaches the same density as the 

stream network, the roads begin 

to become preferential fl ow paths 

for the runoff (Jones and Grant 

1996). The map (Figure 3.20) shows 

the ratio of stream density to road 

density. If the ratio is 1, then the 

road density and the stream density 

are equal. When the ratio is less than 

1 (yellow or red), the road density 

is greater than the stream density. 

There are no sub-watersheds that 

have a road density less than the 

stream density.
37

Impervious surface

The impervious surface area (ISA) 

information is derived from a 

raster dataset (RESAC Impervious 

Surface Area Time Series, version 

1.3) obtained from the Mid-Atlantic 

Regional Earth Science Applications 

Center (RESAC) and the Woods Hole 

Research Center. There are four 

georeferenced rasters containing 

the percent of impervious surface 

for each of the years 1986, 1990, 

1996, and 2000. Dataset values 

indicate the fractional amount of 

impervious material present in a 

single 30 m x 30 m pixel and range 

from 0-100%. These datasets can be 

CHAPTER 3: CURRENT & POTENTIAL STRESSORS

STRESSORS

used to calculate the average percent 

ISA inside any GIS polygon, such as 

a watershed delineation or park 

boundary using the ArcMap Spatial 

Analyst/Zonal Statistics tool.

The calculated impervious surface 

values for each subwatershed were 

categorized and mapped (Figure 

3.21). The 10% impervious surface 

threshold (Arnold and Gibbons 

1996) was used to defi ne the break 

between good and fair watershed 

condition. Impervious surface greater 

than 30% was defi ned as having 

severe stream degradation (Arnold 

and Gibbons 1996). 

36 NCRN I&M

Figure 3.21. GIS 

data layer36 showing 

percent impervious 

surface in and 

around Rock Creek 

Park, Washington, 

D.C., in 2000.

1.6 km

N

Rock Creek Park boundary

100%

0%

Impervious surface:

Impervious Surface
38

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

38

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

The velocity of 

stormwater fl ows 

erode streambanks 

and scour 

streambeds.

LEFT and RIGHT: 

As impervious 

surfaces increase, 

so can stormwater 

runoff volumes and 

pollutant levels in 

park streams.

IAN IAN

IAN
39

Literature cited (Chapter 3)

Arnold Jr, C.L. and C.J. Gibbons. 1996. 

Impervious surface coverage. Journal 

of the American Planning Association 

62(2): 243-269.

Bechtold, T., D. Havlick, and K. 

Stockmann. 1996. Analysis of Road 

Densities in Selected Grizzly Bear 

Management Units in the Northern 

Rockies. ESRI Proceedings of User 

Conference. http://proceedings.esri.

com/library/userconf/proc96/to450/

pap413/p413.htm.

Haynes, R.W., R.T. Graham, and T.M. 

Quigley (Eds.). 1996. A Framework 

for Ecosystem Management In the 

Interior Columbia Basin And Portions 

of the Klamath and Great Basins. U.S. 

Forest Service and U.S. Bureau of Land 

Management with assistance from the 

Pacifi c Northwest Forest Experiment 

Station. PNW-GTR-374. 75 p.

Jones, J.A. and G.E. Grant. 1996. Peak 

fl ow responses to clear-cutting and 

roads in small and large basins, western 

Cascades, Oregon. Water Resources 

Research 32(4): 959-974.

Norris, M., J.P. Schmit and J. Pieper. 2007. 

National Capital Region Network 

2005-2006 Water Resources Monitoring 

Report. Natural Resource Program 

Center, Fort Collins, CO. NPS/NCRN/

NRTR - 2007/066.

U.S. Census Bureau. 2000. http://www.

census.gov/geo/www/tiger/index.html.

CHAPTER 3: CURRENT & POTENTIAL STRESSORS

STRESSORS
40

Tom Paradis

Cardinal Flower (Lobelia cardinalis), a native wildfl ower found in Rock Creek Park.
41

Chapter 4: Metrics & Thresholds

Introduction

Utility of thresholds

A natural resource condition 

assessment requires the 

establishment of criteria for defi ning 

ecological condition and the current 

assessment was based upon explicitly 

defi ned threshold values. Even 

though increasing scientifi c research 

has been focused upon defi ning 

ecological thresholds, uncertainty 

in defi nition as well as spatial and 

temporal variability has often led 

to disagreement on specifi c values 

(Groffman et al. 2006, Huggett 

2005). Even with the defi nition 

of agreed-upon thresholds, there 

is still the question of how best 

to use these threshold values in a 

management context (Groffman 

et al. 2006). Recognizing these 

challenges, thresholds can still be 

effectively used to track ecosystem 

change and defi ne achievable 

management goals (Biggs 2004). 

As long as threshold values are 

clearly defi ned and justifi ed, they 

can be updated in the light of new 

research or management goals 

and can therefore provide an 

important focus for the discussion 

and implementation of ecosystem 

management (Jensen et al. 2000, 

Pantus and Dennison 2005). 

Defi nition and types of 

thresholds

A threshold indicates a tipping point 

or zone where current knowledge 

predicts an abrupt change in an 

aspect or some aspects of ecosystem 

condition. More generally, however, 

thresholds represent an agreedupon value or range indicating 

that an ecosystem is moving away 

from a desired state and towards 

an undesirable ecosystem endpoint 

(Biggs 2004, Bennetts et al. 2007). 

Recognizing that many managed 

systems have multiple and broadscale stressors, another perspective 

is to defi ne a threshold as the level 

of impairment that an environment 

can sustain before resulting in 

signifi cant (or perhaps irreversible) 

damage (Hendricks and Little 

2003). Three types of thresholds 

are used for different aspects of 

natural resource management and 

all can provide useful information 

for the assessment of natural 

resource condition. These thresholds 

are management, ecological, or 

regulatory, and while in some cases 

they overlap (or are the same), 

these thresholds often provide 

different information as a result of 

being established for very different 

purposes (Figure 4.1; Bennetts et al. 

2007).

high

low

threshold 

type

explanation

Metric value

(monitoring result)

degraded

low Ecosystem condition

REGULATORY

THRESHOLD

ALTHOUGH ECOSYSTEM MAY

HAVE CHANGED, IT IS NOW

ALSO UNSAFE FOR HUMANS

FEATURES OF THE

ECOSYSTEM PREDICTED TO

CHANGE

INSTIGATES ACTION TO

MAINTAIN ECOSYSTEM IN

DESIRED STATE

ECOLOGICAL

THRESHOLD

MANAGEMENT

THRESHOLD

Figure 4.1. 

Conceptual 

relationship 

between ecosystem 

condition and the 

different types of 

thresholds. In all 

cases, it is presumed 

that the metric is 

well-studied with a 

reliable measurement 

protocol and wellunderstood responses 

(e.g., available large 

spatio-temporal data 

sets). 

metrics & thresholds

A referenced justifi cation to the use of thresholds in assessment as well as establishing 

thresholds for the 29 metrics used in this natural resource condition assessment.
42

ROCK CREEK PARK: NATURAL RESOURCE CONDITION ASSESSMENT

Management thresholds are 

intended to instigate changes 

in management activity so as to 

maintain the natural resources of 

an ecosystem in a desired state. 

Therefore, these are likely to be the 

most conservative thresholds as it is 

necessary for management responses 

to occur before an ecological 

threshold is passed (Figure 4.1).

Ecological thresholds are based on 

best current scientifi c understanding 

and indicate a value where large 

changes in an ecosystem (and 

therefore natural resource values) 

are predicted (Figure 4.1). This 

defi nition includes the concept of 

‘critical loads,’ as both ecological 

thresholds and critical loads 

estimate a metric value expected 

to be associated with change in the 

ecosystem. The difference is that an 

ecological threshold is based upon 

a response metric while a critical 

load relates to a known amount 

of some input to the system. Both 

ecological thresholds and critical 

loads are often determined by large 

modeling studies across multiple sites 

in varying ecosystem condition, e.g., 

the ecological threshold for benthic 

index of biologic integrity (Stribling 

et al. 1998) and critical loads for 

atmospheric nitrogen oxide and 

sulfur dioxide deposition (Dupont et 

al. 2005). If changes in an ecosystem 

begin without early warning to 

initiate a management response 

(e.g., no management threshold 

exists), and the change continues 

past the ecological threshold (so that 

the ecosystem changes and natural 

resource values become impacted) 

then regulatory thresholds become 

relevant.

Regulatory thresholds are likely to 

be the least conservative threshold 

as they are frequently based on 

an aspect of the ecosystem posing 

a threat to human health (e.g., 

mercury concentration in fi sh; 

Meili et al. 2003), in which case the 

ecosystem may well have already 

entered a degraded condition 

(Figure 4.1). 

Process of threshold 

determination

Within this report, a range of 

management, ecological, and 

regulatory thresholds were 

ultimately used, although ecological 

thresholds were used preferentially. 

One very helpful resource was 

the report by Hendricks and Little 

(2003) to the U.S. Environmental 

Protection Agency (U.S. EPA) 

specifi cally working towards the 

establishment of environmental 

thresholds for multiple metrics. U.S. 

EPA documentation also provided 

a basis for Air Quality (National 

Ambient Air Quality Standards) 

and Water Quality (Freshwater 

Recreational Standards) thresholds, 

which were supplemented by 

scientifi c literature to clarify whether 

thresholds could be considered as 

ecologically relevant, rather than 

simply regulatory (Tables 4.1, 4.2). 

Thresholds for Biodiversity metrics 

were largely based on National 

Park Service (NPS) management 

thresholds, and so the scientifi c 

literature was further investigated 

for experimental or correlative 

justifi cation of these thresholds 

(Table 4.3). Finally, the thresholds 

established for Ecosystem Pattern 

and Processes metrics were based on 

research studies, some of which are 

ongoing within the National Capital 

Region Network (Townsend et al. in 

prep.; Table 4.4). 
43

Metric Threshold Justifi cation Threshold source

Ozone 0.075 ppm for 

the 3-yr mean of 

4th-highest daily 

maximum 8-hr 

average

The ozone threshold was based on 

human health, but is also appropriate 

for plant health. Ozone was sampled 

on an hourly basis. An hourly value 

was calculated (mean of 4 hours 

before and after), recording the 

maximum 8-hr average value per day. 

For each year the 4th-highest daily 

value was recorded and then a 3-yr 

mean was calculated.

U.S. EPA 2004 

NAAQS 2008 

http://cfpub.epa.gov/ncea/cfm/

recordisplay.cfm?deid=149923

Total nitrate 

deposition

Forest: 15 kg ha-1 yr -1

Other: 10 kg ha-1 yr -1

(annual total per 

site)

The nitrate threshold was based on 

maintaining ecosystem structure and 

function. Annual total deposition 

was used—total NO3

-

 deposition was 

calculated as 1.036 x wet deposition.

Greenfelt and Thornelof 1992 

Dupont et al. 2005

Wet sulfate 

deposition

10 kg ha-1 yr -1

(annual total per 

site)

The sulfate threshold was based on 

limiting acidifi cation of sensitive fresh 

waters.

Schindler 1988

Dupont et al. 2005

Particulate

matter (soot;

PM2.5)

15 μg m-3

(annual arithmetic 

mean)

35 μg m-3

(24-hr total)

The soot threshold was based upon 

human health and visibility. 24-hr 

threshold is 3-yr mean of annual 

98th percentile (daily measurement). 

Annual threshold is 3-yr mean 

of annual means (based on daily 

measurement). 

NAAQS 2008

U.S. EPA 2004a

Mercury 

deposition

2 ng L-1

(annual mean)

This modeled value corresponds to an 

inland fi sh tissue concentration of 0.5 

mg methylmercury kg-1 wet weight.

Meili et al. 2003 

Hammerschmidt and Fitzgerald 

2006

Table 4.1. Thresholds for Air Quality metrics.

CHAPTER 4: METRICS & THRESHOLDS

Vehicle exhaust 

contributes to 

increased nitrate 

deposition and 

atmospheric soot 

concentrations.

Sierra Club

metrics & thresholds
44

ROCK CREEK PARK: NATURAL RESOURCE CONDITION ASSESSMENT

Metric Threshold Justifi cation Threshold source

pH 6.0  pH  8.5

(monthly instantaneous 

measurements)

Extreme pH values limit suitability of 

habitat for biota, e.g., salamander 

larvae abundance are reduced at 

extreme pH, directly, and indirectly by 

reducing available food. 

DCMR 2005 

U.S. EPA freshwater 

recreation standards 

2005

Barr and Babbitt 2002 

Dissolved oxygen Instantaneous measures

Jun 1- Jan 31  3.2 mg L-1

Feb 1-May 31  5.0 mg L-1

(monthly instantaneous 

measurements)

Low concentrations of dissolved 

oxygen cause limitation and 

ultimately death of fi sh, benthic 

invertebrates and aquatic plants. 

DCMR 2005

U.S. EPA freshwater 

recreation standards 

2005

Temperature < 32.2°C

(monthly instantaneous 

measurements)

Increased stream water temperature 

is unsuitable for many biota such as 

brook trout. 

DCMR 2005

U.S. EPA freshwater 

recreation standards 

2005

Wehrly et al. 2007

Acid neutralizing 

capacity (ANC)

> 200 μeq L-1

(monthly instantaneous 

measurements)

Threshold based on U.S. EPA “sensitive 

to acidifi cation” standard of 200 μeq 

L-1 . Also justifi ed by relationship to 

stream fi sh and benthic IBI. 

Hendricks and Little 

2003

Roth et al. 1999 

Salinity < 0.25

(monthly instantaneous 

measurements)

Threshold based on U.S. EPA human 

drinking water standards of maximum 

250 mg L-1 chloride ions (equivalent to 

a salinity of 0.25).

U.S. EPA National 

Secondary Drinking 

Water Regulations 2009 

Nitrate < 2 mg L-1

(monthly instantaneous 

measurements)

Threshold based on relationship to 

benthic invertebrate index. 

Roth et al. 1999

Total phosphorus < 36.56 μg L-1

(monthly instantaneous 

measurements)

Threshold based on U.S. EPA 

nutrient ecoregional criteria, to 

maintain baseline conditions with 

minimal impact from anthropogenic 

eutrophication. 

U.S. EPA 2000

Benthic index of 

biotic integrity 

(IBI)

Benthic IBI > 3

(once off sample per site)

Threshold based on statewide 

assessment of benthic communities; 

resulting in the scale: 1.0-1.9 (very 

poor), 2.0-2.9 (poor), 3.0-3.9 (fair), 

4.0-5.0 (good).

Stribling et al. 1998 

Hilderbrand et al. 2007

Physical habitat 

index (PHI)

PHI > 42

(once off sample per site)

Threshold based on 1994-1997 

Maryland Biological Stream Survey 

data on the condition of MD streams: 

1-11.9 (very poor), 12-41.9 (poor), 42-

71.9 (fair), 72-100 (good). 

Roth et al. 1999

Table 4.2. Thresholds for Water Quality metrics.
45

Table 4.3. Thresholds for Biodiversity metrics.

Metric Threshold Justifi cation Threshold source

Percent cover of 

herbaceous 

species, woody 

vines, and target 

exotic trees and 

shrubs

< 5% cover. Measured as 

area of ground covered 

by herbs and vines, and 

percent of total basal area 

for shrubs and trees.

(once off sample per site)

This threshold is more than a simple 

presence of these species, but 

an indication that they have the 

potential to increase in abundance, 

displacing native species.

This threshold is a 

guideline to commence 

active management of 

an area by removal of 

these species. 

CHAPTER 4: METRICS & THRESHOLDS

metrics & thresholds

Presence of pest 

species

emerald ash borer: 0%

gypsy moth: 600 egg

masses ha-1

(once off sample per site)

The emerald ash borer threshold is 

based upon any observed presence of 

this pest species being unacceptable. 

The gypsy moth threshold is based on 

documented forest response.

Montgomery 1990

Liebhold et al. 1994

Native seedling 

regeneration

35,000 seedlings ha-1

(once off sample per site)

Based on natural densities of 

seedlings in a healthy and self 

sustaining forest. This threshold may 

vary depending on deer population. 

McWilliams et al. 1995

Carter and Fredericksen 

2007

Marquis et al. 1992

Fish index of 

biotic integrity 

(IBI)

Fish IBI > 3

(once off sample per site)

Based on 1994-1997 data from a total 

of 1,098 sites, sites were classifi ed 

based on physical and chemical data 

and compared to a range of stream 

fi sh related metrics: 1.0-1.9 (very 

poor), 2.0-2.9 (poor), 3.0-3.9 (fair), 

4.0-5.0 (good).

Roth et al. 1998 

Roth et al. 2000

Proportion of 

area occupied 

(PAO) by adult 

amphibians

20% < PAO < 80%

(once off annual sample)

The threshold is based on preserving 

a diverse and abundant population 

of amphibians. Calculated on a 

species-by-species basis; at < 20% 

PAO, a species risks becoming locally 

extinct and > 80% PAO indicates local 

disturbance favoring one species at 

the expense of others. 

Although the technique 

is well established 

(Mackenzie et al. 2005), 

the threshold is a 

guideline currently used 

for management of 

these areas. 

Presence of 

forest interior 

dwelling species 

(FIDS) of birds

> 1 highly sensitive and/or

> 4 sensitive FIDS 

assessment

(one assessment per year)

Threshold is based on bird 

sensitivity to forest fragmentation 

and disturbance both within 

and surrounding a forest patch, 

particularly during the breeding 

season. One highly sensitive species 

indicates high-quality FIDS habitat, 

> 6 highly sensitive species indicates 

exceptional quality habitat, and

< 4 sensitive species indicates severe 

forest fragmentation and poor FIDS 

habitat. 

Jones et al. 2000

White-tailed deer 

density

Forest: < 8 deer km-2

Grassland: < 20 deer km-2

(one assessment per year)

The forest threshold for deer 

abundance is based on a 10 year 

manipulative experiment. The 

grassland threshold is a guideline 

currently used for management of 

these areas. 

Horsley et al. 2003
46

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

46

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table 4.4. Thresholds for Ecosystem Pattern and Processes metrics.

Metric Threshold Justifi cation Threshold source

Percent forest 

(within the park)

59%

(once off assessment)

USGS digital land use data were used 

for forest cover in areas of North 

Carolina, West Virginia, and Alabama 

to determine the critical value of 

59.28%. Forest was chosen as it is a 

dominant vegetation type within the 

region, providing major structure to 

faunal and fl oral communities. 

Gardner et al. 1987

Gardner and O’Neill 

1991

Hargis et al. 1998

Percent forest 

(within the park 

+ 5 times buffer 

area) Figure 2.16.

59%

(once off assessment)

as above as above

Critical dispersal 

threshold index 

(within the park)

Dcrit < 360 m

(once off assessment)

Based on the distance that many small 

mammals and tree seeds can disperse, 

Dcrit is a measure of the distance 

where 75% of forest patches are 

connected (allowing dispersal). 

Townsend et al. in prep 

Bowman et al. 2002

He and Mladenoff 1999

Critical dispersal 

threshold index 

(within the park 

+ 5 times buffer 

area) Figure 2.16.

Dcrit < 360 m

(once off assessment)

as above as above

Impervious 

surface (within 

the park)

10%

(once off assessment)

Studies on many ecosystem 

components such as wetlands, 

fl oral and faunal communities, and 

streambank structure all show signs 

of impact above this impervious 

surface threshold. Recent studies on 

stream macro-invertebrates continue 

to show shifts to tolerant species and 

reductions in biodiversity near this 

threshold. Overall, < 10% is protected, 

10-30% is impacted and > 30% is 

degraded. 

Arnold and Gibbons 

1996

Lussier et al. 2008

Impervious 

surface (within 

the park + 5 

times buffer 

area) Figure 2.16.

10%

(once off assessment)

as above as above
47

Air Quality

Ozone—

regulatory

Ground-level ozone is regulated 

under the Clean Air Act, and the 

U.S. EPA is required to set standard 

concentrations for ozone (U.S. EPA 

2004). In 1997, the ozone threshold 

was set by the National Ambient 

Air Quality Standards (NAAQS) as 

0.08 ppm (U.S. EPA 2006), but has 

recently been revised and lowered to 

0.075 ppm (NAAQS 2008), where the 

threshold concentration is the threeyear average of the fourth-highest 

daily maximum eight-hour average 

ozone concentration measured 

at each monitoring station. In 

humans, ozone can cause a number 

of health-related issues, such as 

lung infl ammation and reduced 

lung function, which can result in 

hospitalization. Concentrations of 

0.12 ppm can be harmful with only 

short exposure during heavy exertion 

such as jogging, while similar 

symptoms can occur from prolonged 

exposure to concentrations of 0.08 

ppm ozone (McKee et al. 1996). One 

study on 28 plant species, where 

plants were exposed for between 

three and six weeks, showed foliar 

impacts including premature 

defoliation in all species at ozone 

concentrations between 0.06 and 

0.09 ppm (Kline et al. 2008). This 

suggests that a specifi cally plantbased ecological threshold would 

likely be lower than the regulatory 

0.075 ppm (Kline et al. 2008). 

Wet nitrate deposition—

ecological

NPS Air Resources Division has 

estimated that natural background 

deposition of nitrogen in the eastern 

United States is 0.5 kg ha-1 y-1 (NPS 

2005). For deciduous forest habitats, 

greater than 15-20 kg ha-1 y-1 nitrate 

can result in nutrient imbalances 

and changes to plant morphology 

such as increased shoot-root ratios 

(SAR 1995). Dupont et al. (2005) 

suggest a wet deposition target load 

for freshwater Canadian lakes of 

CHAPTER 4: METRICS & THRESHOLDS

Atmospheric 

ozone and soot 

concentrations can 

negatively affect the 

health of joggers on 

park trails.

Bryon Powell

metrics & thresholds
48

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

48

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

10 kg ha-1 y-1 for nitrate deposition. 

This target load is intended to be 

the highest concentration of these 

chemicals that will not lead to longterm harmful effects on ecosystem 

structure and function (Dupont et al. 

2005).

Wet sulfate deposition—

ecological

NPS Air Resources Division has 

estimated that natural background 

deposition of sulfur in the eastern 

United States is 0.5 kg ha-1 y-1 (NPS 

2005). Threshold amounts as low 

as 2.7-6.7 kg S ha-1 y-1 have been 

recommended for oligotrophic lakes 

and streams in Canada (Hendricks 

and Little 2003), and 10 kg S ha-1

y-1 for Canadian freshwater lakes in 

general has been suggested (Dupont 

et al. 2005). Studies within the U.S., 

assessing the correlation of lake pH 

values and sulfur deposition rates, 

have also concluded that loading 

above 10 kg S ha-1 y-1 can be expected 

to cause some degradation (due 

to acidifi cation) of sensitive fresh 

waters (Schindler 1988). 

Particulate matter (soot)—

regulatory

Ground-level particulate matter 

(soot) is regulated under the Clean 

Air Act, and the U.S. EPA is required 

to set standard concentrations for 

airborne particulates (U.S. EPA 2004). 

The particulate matter threshold set 

by the National Ambient Air Quality 

Standard in 1997 was 65 μg m-3

(U.S. EPA 2004a), however this has 

recently been revised and lowered to 

35 μg m-3 (NAAQS 2008), where the 

threshold concentration is the threeyear average of the annual 98th 

percentile concentration, measured 

daily at each monitoring station. 

The equivalent concentration of this 

threshold as an annual arithmetic 

mean is 15 μg m-3. Fine particles 

(PM2.5, particles < 2.5 μm diameter) 

are emitted as smoke from power 

The red-backed 

salamander 

(Plethodon cinereus), 

found in Rock Creek 

Park, can be effected 

by extreme soil 

acidity.

Brian Gratwicke, DCNATURE.com
49

plants, gasoline and diesel engines, 

wood combustion, smelters, steel 

mills, and forest fi res or are the result 

of chemical reactions such as the 

release of sulfur dioxide or nitrogen 

dioxide. A large review conducted by 

the U.S. EPA as part of the revision 

of the regulatory threshold found 

that airborne soot can aggravate 

lung disease, and cause; non-fatal 

heart attacks, asthma attacks, acute 

bronchitis, increased respiratory 

infection, coughing, wheezing, 

shortness of breath, and changes in 

lung function (U.S. EPA, 2006a). 

Mercury deposition—

regulatory

The threshold value of 2 ng L-1 in rain 

is an indirect modeled estimate of 

rainfall mercury concentrations that 

result in a mercury concentration of 

0.5 mg kg-1 wet weight within inland 

fi sh species (Meili et al. 2003). The 

authors do concede that this value is 

for low organic soils, as highly humic 

soils are known to potentially store 

large amounts of mercury which can 

slowly leach into inland waters, in 

some cases contributing much more 

to mercury concentrations than 

current atmospheric deposition (Meili 

et al. 2003). Currently, the U.S. EPA 

also has a lower recommended fi sh 

tissue regulatory maximum of 0.3 mg 

kg-1 wet weight, which would result 

in reducing the modeled atmospheric 

deposition threshold (U.S. EPA 2001). 

Human and mammalian regulatory 

thresholds are based on the effects 

of exposure. In utero exposure can 

cause mental retardation, cerebral 

palsy, deafness, blindness and 

dysarthria (speech disorder) and 

adult exposure can cause motor 

dysfunction and other neurological 

and mental impacts (U.S. EPA 

2001). Avian species are particularly 

susceptible as mercury reduces 

reproductive potential. Measured 

atmospheric wet and dry mercury 

deposition trends from west to east 

across North America can also be 

measured in the common loon (Gavia 

immer), and throughout North 

America in mosquitoes (Evers et al. 

1998, Hammerschmidt and Fitzgerald 

2002). Mercury is also recognized to 

have a toxic effect on soil microfl ora, 

although no ecological depositional 

threshold is currently available (Meili 

et al. 2003). 

CHAPTER 4: METRICS & THRESHOLDS

Older coal-fi red 

power plants, in 

particular, can be 

a major source of 

particulate and 

atmospheric mercury 

pollution.

Sierra Club

metrics & thresholds
50

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

50

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Water Quality

pH, dissolved oxygen, 

temperature—

regulatory

The District of Columbia Municipal 

Regulations (DCMR 2005) have 

classifi ed streams on the basis of 

their current and future uses. These 

categories determine the water 

quality standards that are applied 

to Rock Creek and its tributaries. 

Rock Creek and its tributaries 

are designated for benefi cial 

use as primary and secondary 

contact recreation (A, B), aesthetic 

enjoyment (B), protection and 

propagation of fi sh, shellfi sh, and 

wildlife (C), protection of human 

health related to consumption of 

fi sh and shellfi sh (D), and navigation 

(E) (DCMR 2005). In addition, Rock 

Creek and its tributaries have been 

designated as “Special Waters of 

the District of Columbia” which 

indicates that the “surface waters are 

of water quality better than needed 

for the current use or have scenic 

or aesthetic importance” (DCMR 

2005). The thresholds for dissolved 

oxygen concentration, pH, and water 

temperature are determined from 

these designated benefi cial uses. 

The regulated range for pH is 6.0-

8.5 (DCMR 2005). Salamanders are 

susceptible to extreme pH values and 

can be limited by food availability 

even at less extreme acidifi cation 

(Barr and Babbitt 2002). The dissolved 

oxygen concentration is required to 

be greater than 5 mg L-1 from Feb 

1-May 31 and above 3.2 mg L-1 from 

Jun 1-Jan 31 (DCMR 2005). In all 

cases, water temperature is regulated 

to be less than 32.2°C (DCMR 2005), 

which is greater than the critical 

thermal maximum for Brook Trout, 

28.3-29°C (Wehrly et al. 2007).

Acid neutralizing capacity—

ecological

The acid neutralizing capacity (ANC) 

threshold was developed by the 

Maryland Biological Stream Survey 

Tom Paradis

Spotfi n shiners 

(Cyprinella 

spiloptera), found in 

Rock Creek, require 

good water quality 

and intact streams.

Brian Gratwicke, DCNATURE.com
51

(MBSS) program after their fi rst 

round of sampling (1995-1997). 

The MBSS data were used to detect 

stream degradation so as to identify 

streams in need of restoration and to 

identify ‘impaired waters’ candidates 

(Roth et al 1999). A total of 539 

streams that received a fi sh or benthic 

index of biotic integrity (FIBI or BIBI) 

rating of poor (2) or very poor (1) 

were pooled and fi eld observations 

and site-specifi c water chemistry data 

were used to determine stressors 

likely causing degradation. The 

MBSS then used threshold values to 

indicate stress. The ANC threshold 

for determining degraded streams 

is less than 200 μeq L-1 (Roth et al. 

1999, Hilderbrand et al. 2007). A less 

conservative threshold of 50 μeq L-1

has also been suggested (Hendricks 

and Little 2003, Schindler 1988).

Salinity—

regulatory

Salinity in drinking water is 

regulated by U.S. EPA under the 

National Secondary Drinking Water 

Standards (NSDWS) regulations. These 

regulations control contaminants 

in drinking water and are nonenforceable. The Secondary Maximum 

Contaminant Level (advisory only) for 

salinity is 250 mg L-1 (NSDWS 1997), 

which is equivalent to a salinity of 

0.25. Therefore, the salinity threshold 

for this assessment is < 0.25.

Nitrate—

ecological

The nitrate concentration threshold 

was developed by the MBSS program 

after their fi rst round of sampling 

as described for the ANC threshold. 

The MBSS determined that a nitrate 

concentration of 2 mg L-1 indicated 

stream degradation (Roth et al. 1999, 

Hilderbrand et al. 2007).

Total phosphorus—

ecological

The total phosphorus threshold is 

based on the U.S. EPA Ecoregional 

Nutrient Criteria. These criteria were 

developed to prevent eutrophication 

nationwide and are not regulatory 

(U.S. EPA 2000). The criteria were 

developed as baselines for specifi c 

geographic regions. Rock Creek Park 

is located in Ecoregion IX or the 

Southeastern Temperate Forested 

Plains and Hills region (U.S. EPA 2000). 

The ecoregional reference condition 

value, which is used as the threshold 

for phosphorus, is 36.56 μg L-1 (U.S. 

EPA 2000).

Benthic index of biotic 

integrity—ecological

The aquatic macroinvertebrates 

threshold is based on the MBSS 

interpretation of the benthic index 

of biotic integrity (IBI). The IBI scores 

range from 1 to 5 and are calculated 

by comparing the site’s benthic 

assemblage to the assemblage 

found at minimally impacted sites 

(Hilderbrand et al. 2007). An IBI score 

of 3 means that a site is considered 

to be comparable (not signifi cantly 

different) to reference sites. A score 

greater than 3 indicates that a 

site is in better condition than the 

reference sites. Any sites with IBIs 

less than 3 are in worse condition 

than reference sites (Roth et al. 

1999, Hilderbrand et al. 2007), and 

the entire scale is 1.0-1.9 (very 

poor), 2.0-2.9 (poor), 3.0-3.9 (fair), 

4.0-5.0 (good; Stribling et al. 1998). 

Therefore, the threshold for aquatic 

macroinvertebrates is an IBI greater 

than 3, indicating that a site is in, at 

least, reference condition (Roth et al. 

1999).

CHAPTER 4: METRICS & THRESHOLDS

metrics & thresholds
52

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

52

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Physical habitat index —

ecological

For the physical habitat index (PHI), 

in-stream and near-stream habitat 

measures of fi rst through thirdorder streams are recorded between 

June and September at the same 

time as the fi sh are being sampled 

(Hilderbrand et al. 2007). This 

sampling period was chosen because 

the low fl ow conditions are typically 

limiting to the abundance of lotic 

(living in moving water) fi sh. The PHI 

consists of measures of bank stability, 

epibenthic substrate, shading, 

remoteness, riparian width, riffl e 

quality, instream wood, instream 

habitat quality, and embeddedness. 

Sites are given scores for each of the 

applicable categories and then those 

scores are adjusted to a percentile 

scale (Hilderbrand et al. 2007). The 

PHI threshold was developed by the 

MBSS program after their fi rst round 

of sampling as described for the ANC 

threshold. The MBSS determined 

the scale for PHI values to be 1-11.9 

(very poor), 12-41.9 (poor), 42-71.9 

(fair), 72-100 (good; Roth et al. 1999, 

Hilderbrand et al. 2007).

Biodiversity

Percent cover of 

herbaceous species, 

woody vines, and 

target exotic trees and shrubs—

management

Invasive exotic plants may compete 

with native plants and therefore lead 

to a reduction in biodiversity of the 

native fl ora (Mack et al. 2000). The 

current threshold is that abundance 

of these plants should not exceed 5% 

cover, measured as area of ground 

covered by herbs and vines, and 

percent of total basal area for shrubs 

and trees. The threshold is intended 

to indicate both the simple presence 

of these exotic species, and also 

that abundance of these species is 

suffi cient to potentially establish and 

spread. 

Presence of pest species—

management, ecological

Emerald ash borer (Agrilus 

planipennis) was fi rst observed in 

the U.S. in 2002, and since then 

has been responsible for the death 

of an estimated 15-20 million ash 

LEFT: A Rock Creek 

Park stream bed 

is scoured by fl ash 

fl ooding.

RIGHT: Lesser 

celandine 

(Ranunculus fi caria) 

is an invasive exotic 

plant that spreads 

rapidly across the 

forest fl oor to 

form a blanket of 

leaves which native 

species are unable to 

penetrate. 

IAN Leslie J. Mehrhoff, U of Conn, bugwood.org
53

trees in southern Michigan alone 

(McCullough and Siegert 2007). 

A total of 16 ash species in North 

America are potentially affected by 

this invasive exotic species, which 

has now been observed in dozens 

of locations outside of southern 

Michigan (McCullough and Siegert 

2007). The drastic effects and 

potential for forest damage result in 

the threshold being any observations 

of adults or larvae. The gypsy moth 

(Lymantria dispar) was accidentally 

introduced to North America in the 

late 1860s and has spread widely, 

resulting in an estimated 40 million 

acres of forest defoliation during the 

1980s alone (Liebhold et al. 1994). 

A standard threshold of 600 egg 

masses per hectare (250 per acre) has 

been established as a management 

threshold (Montgomery 1990, 

Liebhold et al. 1994); however, forest 

response is known to be very variable 

between 240 and 2400 egg masses 

per hectare. As a result, ecological 

thresholds may be higher than 

600 egg masses ha-1. Observations 

suggest 1,240-1,850 egg masses per 

hectare are likely to lead to > 30% 

defoliation, 1,730-2,220 egg masses 

per hectare are likely to result in 

growth loss (i.e., > 40% defoliation), 

and 2,470-3,460 egg masses per 

hectare are likely to result in tree 

mortality (Liebhold et al. 1994). 

Native seedling regeneration—

ecological

The ecological seedling regeneration 

threshold of 35,000 seedlings ha-1

is based upon seedling numbers in 

a mature, non-industrial private 

forestland in south-central Virginia 

(Carter and Fredericksen 2007). 

However, some estimates of native 

regeneration for silviculture under 

different deer grazing scenarios are 

much higher—15 million seedlings 

per hectare (all desirable species), 

under very low, and as many as 21 

million seedlings per hectare (all 

desirable species), under very high, 

deer grazing pressure (Marquis et al. 

1992). 

Fish index of biotic integrity—

ecological

A threshold value of 3 was used as 

an ecological threshold indicating 

attainment of overall reference 

ecosystem condition. The fi sh 

index of biotic integrity (FIBI) was 

proposed as a way to provide 

a more informative measure 

of anthropogenic infl uence on 

fi sh communities and ecological 

integrity than measurements of 

physiochemical metrics alone 

(Karr 1981). The metric was then 

adapted and validated for streams of 

CHAPTER 4: METRICS & THRESHOLDS

www.hgic.umd.edu

A gypsy moth shown 

here in three life 

stages: pupa, egg 

mass, and moth.

The Denil fi sh ladder 

at Peirce Mill Dam 

was installed in 

2006 to enable the 

upstream migration 

of migratory fi sh such 

as the alewife (Alosa 

pseudoharengus) and 

the blueback herring 

(Alosa aestivalis).

metrics & thresholds

Tom Paradis
54

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

54

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Maryland using a reference condition 

approach, fi nding that 29% of 

stream sites sampled in Maryland 

were in poor or very poor condition 

(Roth et al. 1998, Roth et al. 2000). 

The IBI scores range from 1-5 with a 

score greater than 3 indicating that 

a site is considered to be comparable 

to or better than reference sites 

(Roth et al. 2000). 

Proportion of area occupied by 

adult amphibians—

management

The threshold of between 20 and 

80% area occupied (PAO) is currently 

used as a management threshold, 

intended to maintain abundant and 

diverse amphibian communities. The 

percent area occupied is calculated 

according to whether amphibians 

are: 1) present and detected, 2) 

present and not detected, or 3) not 

present, with a probabilistic function 

to determine differences between 

not present versus present but not 

detected (Bailey et al. 2007). The 

probabilistic function has been 

developed for diverse faunal species 

(Mackenzie et al. 2003).

Presence of forest interior 

dwelling species of birds—

ecological

Presence of bird species can 

effectively provide a bio-indicator 

of subtle or unexpected changes in 

environmental condition (Koskimies 

1989). Throughout Maryland, there 

was a documented 63% decline 

in individual birds of neotropical 

origin (including forest interior 

dwelling species [FIDS]) between 

1980 and 1989 (Jones et al. 2000). 

This represented a continuation of 

documented declines at some sites 

between 1940 and 1980 (Terborgh 

1992). The presence of sensitive FIDS 

is used as an indicator of high-quality 

forest interior habitat. The Guide to 

Conservation of FIDS lists 25 species 

that can potentially breed in critical 

areas in Maryland. Thirteen of the 25 

species are considered ‘highly areasensitive’ and presence of one highly 

area-sensitive species indicates highquality forest interior habitat (Jones 

et al. 2000; Appendix Table A.14). 

Presence of six or more highly areasensitive species indicates exceptional 

forest interior habitat. The other 

LEFT: The shaded 

wetlands, seeps, 

streams, and wooded 

habitats of Rock 

Creek Park are home 

for several amphibian 

species, such as this 

northern two-lined 

salamander, Eurycea 

bislineata.

RIGHT: Bird watching 

in Rock Creek Park, 

Washington, D.C.

Brain Gratwicke, DCNATURE.com NPS
55

12 FIDS are less area-sensitive; but 

they still require large forest tracts 

for stable populations (Jones et al. 

2000). Using this information, the 

ecological threshold was based on 

the presence of appropriate habitat 

for forest interior dwelling species of 

birds and defi ned as observation of 

at least four FIDS or one highly areasensitive species. In both cases, these 

birds must be observed in probable 

or confi rmed breeding status (Jones 

et al. 2000). 

White-tailed deer density—

forest: management, ecological; 

grassland: management

The forest threshold for white-tailed 

deer density (8.0 deer km-2) is a wellestablished ecological threshold, 

and this threshold is also used as 

the management threshold. Species 

richness and abundance of herbs and 

shrubs, although showing change 

in some studies at densities as low 

as 3.7 deer km-2, are consistently 

reduced as deer densities approach 

8.0 km-2 (Decalesta 1997). One 

large manipulation study in central 

Ryan Valdez, DCNATURE.com

Massachusetts found that deer 

densities of 10-17 km-2 inhibited 

the regeneration of understory 

species, while densities of 3-6 km-2

supported a diverse and abundant 

forest understory (Healy 1997). 

There are multiple sensitive species 

of songbirds that cannot be found 

in areas where deer grazing has 

removed understory vegetation 

needed for nesting, foraging, and 

protection. Even though songbird 

species vary in how sensitive they 

are to increases in deer populations, 

these changes generally occur at 

deer densities greater than 7.9 

km-2 (Decalesta 1997). In contrast, 

the grassland (or agricultural land) 

management threshold for deer 

abundance is less well-studied or 

justifi ed but is currently 20 deer km-2. 

Studies of national parks within the 

National Capital Region (Antietam, 

Monocacy, and Chesapeake and Ohio 

Canal) have shown that the current 

abundances of 45-54 deer km-2 cause 

signifi cant damage to agricultural 

crops maintained as grassland 

habitat (Stewart et al. 2007). 

Overgrazing by 

large numbers of 

white-tailed deer 

in Rock Creek Park 

can degrade forest 

conditions.

CHAPTER 4: METRICS & THRESHOLDS

metrics & thresholds
56

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

56

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Ecosystem Pattern 

and Processes

Percent forest—

ecological

Modeling studies have found that in 

ecological systems, there is a tipping 

point of forest cover below which 

a system becomes so fragmented 

that it no longer functions as a 

single system (Hargis et al. 1998). 

This ‘percolation’ theory was initially 

developed in metallurgy to assess 

coherence of material aggregates 

(Gardner et al. 1987). USGS digital 

land use data were used for forest 

cover in areas of North Carolina, 

West Virginia, and Alabama to 

determine the critical value of 

59.28% (Gardner et al. 1987). Forest 

was chosen as it is a dominant 

vegetation type within the region, 

providing major structure to faunal 

and fl oral communities.

Critical dispersal threshold 

index—

ecological

The critical dispersal threshold index 

(Dcrit; distance < 360 m) is based 

on the distance that many small 

mammals and tree seeds can disperse 

(He and Mladenoff 1999, Bowman 

et al. 2002). Dcrit is a measure of the 

distance where 75% of forest patches 

are connected, therefore allowing 

dispersal (Townsend et al. in prep.). 

From 13 tree species, an effective 

dispersal distance of 65 ± 15 m (mean 

± standard error) has been calculated, 

indicating on average a 95% 

probability of effective dispersal over 

this distance. The maximum dispersal 

distance for these same species was 

997 ± 442 m, indicating rare (< 1% 

probability) success of dispersal at this 

distance (He and Mladenoff 1999). 

Impervious surface—

ecological

A study carried out in coastal New 

Jersey demonstrated measurable 

effects of impervious surface on 

pH and specifi c conductance at 

impervious surface cover as low as 

2%, and recommended a threshold 

for those systems between 2.4% 

and 5.1% (Conway 2007). Percent 

urban land is highly correlated to 

impervious surface and can provide 

a good approximation of watershed 

Inside Rock Creek 

Park, the grounds 

are threaded with 

roads, bridges, and 

parking lots, all 

adding impervious 

surface and forest 

fragmentation.

Tom Paradis
57

degradation due to increases of 

impervious surface. This correlation 

occurs because residential land use 

ranges from 12-65% impervious 

surface (Conway 2007). 

The three Ecosystem Pattern and 

Processes metrics were calculated 

at two scales: 1) within the park 

boundary, and 2) within the park 

boundary plus an area fi ve times 

the total area of the park, evenly 

distributed as a ‘buffer’ around the 

entire park boundary (Figure 2.7). 

The purpose of this analysis was to 

assess the infl uence on ecosystem 

processes of land use immediately 

surrounding the park.

Literature cited (Chapter 4)

Arnold Jr, C.L. and C.J. Gibbons. 1996. 

Impervious surface coverage. Journal 

of the American Planning Association 

62(2): 243-269.

Bailey, L.L., E.H. Campbell-Grant, 

and P. Mattfeldt. 2007. National 

Capital Region Network Amphibian 

Monitoring Protocol. http://science.

nature.nps.gov/im/monitor/VitalSigns/

BrowseProtocol.aspx.

Barr, G.E. and K.J. Babbitt. 2002. Effects 

of biotic and abiotic factors on the 

distribution and abundance of larval 

two-lined salamanders (Eurycea 

bislineata) across spatial scales. 

Oecologia 133:176-185.

Bennetts, R.E., J.E. Gross, K. Cahill, C. 

McIntyre, B.B. Bingham, A. Hubbard, 

L. Cameron, and S.L. Carter. 2007. 

Linking monitoring to management 

and planning: assessment points as 

Surburban 

neighborhoods that 

border Rock Creek 

Park, such as this 

one, add to the 

high percentage 

of surrounding 

impervious surface.

Tom Paradis

CHAPTER 4: METRICS & THRESHOLDS

metrics & thresholds
58

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

58

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

a generalized approach. The George 

Wright Forum 24(2): 59-79.

Biggs, H.C. 2004. Promoting ecological 

research in national parks – a South 

African perspective. Ecological 

Applications 14(1): 21-24.

Bowman, J., A. Jochen, G. Jaeger, and 

L. Fahrig. 2002. Dispersal distance of 

mammals in proportion to home range 

size. Ecology 83(7): 2049-2055.

Carter, W.K. and T.S. Fredericksen. 2007. 

Tree seedling and sapling density and 

deer browsing incidence on recently 

logged and mature non-industrial 

private forestlands in Virginia, USA. 

Forest Ecology and Management 242: 

671-677.

Conway, T.M. 2007. Impervious surface 

as an indicator of pH and specifi c 

conductance in the urbanizing coastal 

zone of New Jersey, USA. Journal 

of Environmental Management 85: 

308-316.

DCMR. 2005. District of Columbia 

Municipal Regulations. Amendment 

to chapter 11 of Title 21, sections 

1100 to 1106. http://www.epa.gov/

waterscience/standards/wqslibrary/dc/

dc_3_register.pdf.

Decalesta, D.S. 1997. Deer Ecosystem 

Management. In: McShea, W.J., H.B. 

Underwood, and J.H. Rappole (eds). 

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metrics & thresholds

CHAPTER 4: METRICS & THRESHOLDS
62

Ryan Valdez, DCNATURE.com

White-tailed deer (Odocoileus virginianus) of Rock Creek Park.
63

Chapter 5: Resource Condition Assessment

Introduction

It is increasingly recognized that 

monitoring data collected for specifi c 

purposes, such as assessing the 

implementation of environmental 

regulations, does not necessarily 

allow for regional assessments of 

ecosystem condition (U.S. EPA 2000, 

2002). As a result, one of the key 

challenges of large-scale monitoring 

programs is to develop integrated 

and synthetic data products that can 

translate a multitude of diverse data 

into a format that can be readily 

communicated to decision-makers, 

policy developers, and the public 

(Fancy et al. 2008). These timely 

syntheses of ecosystem condition 

can provide feedback to managers 

and stakeholders, so that the 

effectiveness of management actions 

as well as future management goals 

can be determined at multiple scales 

(Dennison et al. 2007; Figure 5.1). 

One approach to synthesizing data is 

the development of multiple-metric 

indices to summarize the status of 

many aspects of a community, such as 

fi sh, and then draw inferences on the 

status of the supporting ecosystem 

(Karr 1981). The development of 

combined metrics improved upon a 

traditional approach of acute toxicity 

testing on organisms as toxicity 

limits can show large regional 

differences depending on the local 

environment. Multi-metric indices 

also improved on the use of just 

one measure, such as fi sh biomass 

or abundance, which often show 

complex and variable responses to 

changes in environmental condition 

(Karr 1981). Metrics such as the fi sh 

index of biotic integrity (IBI) and the 

benthic IBI have been widely applied, 

both internationally and locally (in 

Maryland streams), and are seen 

as providing greater insight into 

ecosystem condition than physical 

measurements (e.g., water quality) 

alone, as biological communities 

provide an integrated summary 

of ecosystem condition over time 

(Roth et al. 1998, 2000, Harrison and 

Whitfi eld 2004). Although these 

synthetic indices and bioindicators 

can provide important information 

about overall status of an ecosystem, 

no data, of itself, can improve our 

practice of ecosystem management 

decision making (Carter et al. 2007). 

Therefore, to clearly identify major 

environmental issues and assist in 

directing effective management 

actions, some format of score card 

or report card of multiple metrics is 

necessary (U.S. EPA 2000, 2002). 

ASSESSMENT

Using the data from Chapters 2 and 3 and the thresholds from Chapter 4, the vital signs and 

habitat framework to assess Rock Creek Park’s natural resource condition are presented.

Figure 5.1 Multiple 

spatial scales relevant 

to assessing natural 

resource conditions.

7

3

8

6

4

5

2

10

1

9

a GLOBAL b REGIONAL c WATERSHED d SUB-WATERSHED e PARK

N

2600 km 32 km

N

2 km

N

1 km

N

500 km

N
64

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

64

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

For broad application, a reporting 

framework needs to be fl exible 

because, depending on the spatial 

and temporal scales being assessed 

(Figure 5.1), different metrics 

are most appropriate. While 

development of a ‘regional index 

of biological integrity,’ combining 

multiple synthetic indices (e.g., 

invertebrate, avian, and amphibian 

indices) has been used for midAtlantic forest riparian ecosystems 

(Brooks et al. 1998) and an 

assessment of the 422 km2

 Maryland 

Coastal Bays used an index of water 

quality metrics (Wazniak et al. 2007), 

remote sensing data of impervious 

surface, road density, and vegetation 

cover were used to compare subwatersheds of the 86,752 km2

 Ordos 

Plateau in Inner Mongolia (Ding et 

al. 2008). Spatially explicit regional 

report cards, using biological 

and water quality metrics and 

targeted specifi cally at identifying 

and communicating key issues to 

managers and decision-makers as 

well as at tracking effectiveness of 

management actions over time, 

have been developed for estuaries 

in Moreton Bay, Australia (Pantus 

and Dennison 2005) and Chesapeake 

Bay in the U.S. (Williams et al. in 

press). Integrated assessments of 

multiple metrics using a threshold 

approach have also been applied 

to the comparison of estuaries 

at broad spatial scales (Ferreira 

2000, Kiddon et al. 2003, Bricker 

et al. 2008). Elements of many 

of these assessment approaches 

are appropriate to include in the 

assessment of natural resource 

condition of Rock Creek Park, 

however, some unique challenges 

with respect to available data and 

also the diversity of habitats required 

the use of modifi ed frameworks. 

Rock Creek assessment 

approach

For the assessment of natural 

resource condition within Rock Creek 

Park, two synthetic frameworks were 

applied, both based on categories 

that addressed key structural and 

functional aspects of the ecosystem 

(U.S. EPA 2002). Recognizing the 

large amount of data included 

in this assessment from the NPS 

Inventory & Monitoring Program 

(I&M), the fi rst framework utilized 

was the ecological monitoring 

framework or ‘vital signs’ 

categorization developed by NPS 

I&M (Fancy et al. 2008). Fancy et al. 

(2008) identifi ed a key challenge 

of such large-scale monitoring 

programs to be the development 

of information products which 

integrate and translate large 

amounts of complex scientifi c data 

into highly aggregated metrics for 

communication to policy-makers and 

non-scientists. Aggregated indices 

were developed and presented 

within the current natural resource 

condition assessment for Rock 

Creek Park. More specifi c indices 

and even raw data (Appendix A) 

were also presented to facilitate 

communication of key conclusions to 

scientists and fi eld practitioners and 

to ensure that all approaches and 

calculations were explicit. The second 

framework, using the same data set, 

calculated aggregated condition 

indices based upon the three main 

ecological habitats present within 

Rock Creek Park—Forest, Wetland 

(Inland), and Artifi cial-terrestrial 

Habitats (predominantly managed 

meadows, community gardens, and 

mown lawns with trees and shrubs). 
65

Methods

Ecological monitoring framework

CHAPTER 5: RESOURCE CONDITION ASSESSMENT

ASSESSMENT

An ecological monitoring framework 

has been established by NPS I&M 

(Fancy et al. 2008), based on 

multiple efforts, such as the U.S. EPA 

scientifi c advisory board assessment 

on reporting ecological condition 

(U.S. EPA 2002). The NPS ecological 

monitoring framework has six highlevel data categories; air and climate, 

geology and soils, water, biological 

integrity, human use, and landscapes 

(Fancy et al. 2008). In the assessment 

of natural resource condition of Rock 

Creek Park, data were available for 

four of these six data categories; 

air and climate (Air Quality), water 

(Water Quality), biological integrity 

(Biodiversity), and landscapes 

(Ecosystem Pattern and Processes). 

Air Quality Water Quality Biodiversity Ecosystem Pattern 

and Processes

Entrance to Rock 

Creek Park borders a 

busy roadway.

Lisa Florkowski
66

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

66

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table 5.1. Summary of IUCN major habitat classifi cations (for full listing, see Appendix Table B.1).

IUCN general habitat description # sub-habitats

1 Forest 9

2 Savanna 2

3 Shrubland 8

4 Grassland 7

5 Wetland (Inland) 18

6 Rocky areas (inland cliffs and mountain peaks) 0

7 Caves and non aquatic subterranean 2

8 Desert 3

9 Marine neritic (submerged nearshore, oceanic islands) 10

10 Marine oceanic 4

11 Marine deep benthic 6

12 Marine intertidal 7

13 Marine coastal/supratidal 5

14 Artifi cial-terrestrial 6

15 Artifi cial aquatic 13

16 Other

Habitat framework

2.9), seeps, and springs (Figure 

2.11) were classifi ed as Wetland 

(Inland) Habitat; and canopy gap, 

managed meadows, community 

gardens, and mown lawns with 

trees and shrubs were classifi ed as 

Artifi cial-terrestrial Habitat (Figure 

2.4). To provide a basis for condition 

assessment for each habitat, the 

desired versus degraded extremes 

were conceptually described (Figure 

5.2) based on a series of seven 

metrics which can be used to track 

the relative condition of the habitat 

between these two states. These 

metrics were chosen as being of a 

relevant spatial scale, responsive to 

change, and, where possible, with 

an established ecological threshold 

(Chapter 4, Metrics & Thresholds). 

The habitat list defi ned by the 

International Union for the 

Conservation of Nature (IUCN) was 

chosen as the standard (IUCN 2007). 

The IUCN habitat classifi cation 

includes 16 habitat types at the 

highest level, which are further 

divided into sub-habitats (Table 5.1, 

Appendix Table B.1). A total of three 

general habitat types were defi ned 

for Rock Creek Park (Figure 5.2). To 

determine the habitat types present 

within Rock Creek Park, a classifi ed 

vegetation base map (Figure 2.6) 

was aggregated into general habitat 

types: beech/mixed oak, beech/tulip 

poplar, beech/white oak, chestnut 

oak, loblolly pine/mixed oak, tulip 

poplar, Virginia pine/oak, and 

sycamore/green ash were classifi ed 

as Forest Habitat; streams (Figure 

Forest Wetland (Inland) Artifi cial-terrestrial
67

Figure 5.2. 

Conceptual 

framework for 

desired and degraded 

condition of habitats 

present within Rock 

Creek Park, indicating 

metrics to track 

status of condition. 

CHAPTER 5: RESOURCE CONDITION ASSESSMENT

ASSESSMENT

Desired artificial terrestrial habitat has low 

particulate matter (good visibility) , 

low % impervious surface , and small 

deer populations . Low ozone levels 

result in healthy plants , low sulfate 

deposition results in neutral rain , 

low nitrate deposition is used by 

plants locally , and low mercury 

deposition permits healthy fish.

ROCK CREEK PARK

1 km

Forest (81%)

Wetland (Inland) (2%)

Artificial-terrestrial (17%)

Habitat type

N

Degraded artificial terrestrial habitat has 

high particulate matter (low visibility) , 

high % impervious surface , and large 

deer populations . High levels of 

ozone result in unhealthy plants , 

high sulfate deposition results in acid 

rain , high nitrate deposition 

reaches the water table , and fish may 

die due to high mercury deposition . 

Mercury

Deposition

3 3

3

DEGRADED

DEGRADED

Degraded wetland habitat has eroded 

streambanks and no shade , 

high nutrients and salinity , 

resulting in turbid water , low 

oxygen levels , and low populations 

of fish , amphibians , and 

benthic invertebrates .

Degraded forest habitat has high 

numbers of exotic shrubs and trees , 

high % of impervious surface , 

and large deer populations . 

Native seedling regeneration and 

diversity of forest-dwelling bird

species are low in patch forest 

with high occurance of insect pests .

DEGRADED

DESIRED

DESIRED

Indicators

Desired wetlands habitat has intact 

streambanks with shade 

and sheltering roots and debris , 

low nutrients , and salinity 

resulting in high oxygen , clear

water , and high populations of 

fish , amphibians , and 

Total

Phosphorus

low

Nitrate low

Salinity low

Physical Habitat

Index

high

Area Occupied by

Adult Amphibians

stable

Dissolved

Oxygen

high

 

Benthic

Invertebrates

high

high

high

high

low

unstable

low

low

FOREST HABITAT

WETLAND (INLAND) HABITAT

ARTIFICIAL-TERRESTRIAL HABITAT

Desired forest habitat has low numbers 

of exotic shrubs and trees , low % 

of impervious surface , and small 

deer populations . Native seedling 

regeneration and diversity of 

forest-dwelling bird species are 

high in continuous forest with 

low occurance of insect pests .

low

high

high

low

high

low

low

high

low

low

low

high

high

high

DESIRED

Indicators

Sulfate Wet

Deposition

Particulate

Matter

(soot)

Deer

Population

Nitrate Wet

Deposition

Ozone

Percentage of

Impervious Surface

Percentage of

Impervious Surface

Native Seedling

Regeneration

Presence of Forest

Interior-dwelling

Bird Species

Density of Exotic

Shrubs and Trees

Forest

Connectivity

Deer

Population

Presence of

Insect Pests

Indicators

low

low

low

low

low

low

low

high

high

high

high

high

high

high

3

3

3
68

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

68

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Data and thresholds 

Ecological monitoring framework

A total of 29 metrics across the four 

ecological monitoring framework 

categories were included, each with 

an established threshold and based 

on a categorical scoring of threshold 

attainment (Table 5.2, 5.3; Chapter 

4, Metrics & Thresholds). While some 

metrics were measured at the park 

scale and therefore only have one 

sampling site (e.g., deer density and 

Ecosystem Pattern and Processes

metrics), there are 13 sampling 

sites for Water Quality within Rock 

Creek Park. Temporal intensity of 

measurement also varied between 

metrics, with only single assessments 

of Ecosystem Pattern and Processes

metrics, while Water Quality metrics 

were measured monthly during the 

available data range (Table 5.2). 

All data used in the assessment 

were collected between 2000 and 

2007 (Table 5.2). Data used in the 

assessment were obtained from 

multiple sources, with the Air Quality

data largely coming from national 

air monitoring programs, Water 

Quality and Biodiversity data from 

the NPS I&M monitoring program, 

and Ecosystem Pattern and Processes

data from a collaborative project 

between NPS and the University of 

Maryland Center for Environmental 

Science (Table 5.3). 

IAN

Water sampling in 

the streams of the 

Rock Creek Park 

watershed.
69

CHAPTER 5: RESOURCE CONDITION ASSESSMENT

ASSESSMENT

Table 5.2. Summary of data used in Rock Creek Park natural resource condition assessment.

Metric (by vital sign category) Threshold Sites Samples Period

Air Quality 

Ozone < 0.075 ppm 2 8 2000-2003

Total NO3

-

 deposition (forest habitat) < 15 kg ha-1 yr-1 3 10 2000-2007

Total NO3

-

 deposition (other) < 10 kg ha-1 yr-1 3 10 2000-2007

Wet SO4

 deposition < 10 kg ha-11 yr-1 3 10 2000-2007

Particulate matter (soot; PM2.5) concentration < 15 mg m-3 3 15 2000-2004

Hg deposition < 2 ng L-1 1 86 2004-2006

Water Quality 

pH 6.0  pH  8.5 13 234 2005-2007

Dissolved oxygen June 1-Jan 31:  3.2 mg L-1

 Feb 1-May 31:  5.0 mg L-1 13 241 2005-2007

Water temperature  32.2oC 13 242 2005-2007

Acid neutralizing capacity (ANC)  200 μeq L-1 13 241 2005-2007

Salinity < 0.25 13 219 2005-2007

Aqueous nitrate < 2 mg L-1 13 234 2005-2007

Total phosphorus < 36.56 μg L-1 13 230 2005-2007

Benthic index biological integrity (BIBI) > 3 6 6 2000-2004

Physical habitat index (PHI) > 42 3 8 2000-2004

Biodiversity 

% cover of exotic herbaceous species < 5% (of area) 5 5 2006-2007

Exotic tree/shrub density < 5% (of total basal area) 3 4 2006-2007

Presence of forest pest species < 1% of trees infested 3 3 2006-2007

Native seedling regeneration > 31,875 seedlings ha-1 5 5 2006-2007

Fish index biological integrity (FIBI) > 3 3 6 2000-2004

Prop. of area occupied (PAO) by amphibians 20% < PAO < 80% each spp. Park 9 2005-2007

Presence of forest interior dwelling species > 1 ‘highly sensitive’ FIDS

(FIDS) of birds > 4 ‘sensitive’ FIDS Park 3 2003-2008

Deer density Forest: < 8 deer km-2

 Grassland: < 20 deer km-2 Park 8 2000-2007

Ecosystem Pattern and Processes 

Proportion forest cover (within park) 0.59 Park 1 2001-2002

Prop. impervious surface (within park) 0.1 Park 1 2000

Critical connectivity (Dcrit; within park) < 360 m Park 1 2001-2002

Prop. forest cover (within park) + 5X buffer 0.6 Park 1 2001-2002

Prop. imperv. surface (within park) + 5X buffer 0.1 Park 1 2000

Critical connectivity (within park) + 5X buffer < 360 m Park 1 2001-2002
70

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

70

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table 5.3. Sources of data used in Rock Creek Park natural resource condition assessment.

Metric (by vital sign category) Agency Reference/source

Air Quality 

Ozone NPS ARD (U.S. EPA) NPS CUE 

Total NO3

-

 deposition (forest habitat) NADP http://nadp.sws.uiuc.edu/ 

Total NO3

-

 deposition (cultivated) NADP http://nadp.sws.uiuc.edu/ 

Wet SO4

 deposition NADP http://nadp.sws.uiuc.edu/ 

Particulate matter (soot; PM2.5) concentration IMPROVE http://vista.cira.colostate.edu/improve/ 

Hg deposition MDN-NADP http://nadp.sws.uiuc.edu/mdn/

Water Quality 

pH NPS I&M Norris et al. 2007

Dissolved oxygen NPS I&M Norris et al. 2007

Water temperature NPS I&M Norris et al. 2007

Acid neutralizing capacity (ANC) NPS I&M Norris et al. 2007

Salinity NPS I&M Norris et al. 2007

Aqueous nitrate NPS I&M Norris et al. 2007

Total phosphorus NPS I&M Norris et al. 2007

Benthic index biological integrity (BIBI) NPS I&M, Hilderbrand et al. 2007, 

 Montgomery County Montgomery County DEP

Physical habitat index (PHI) NPS I&M, Hilderbrand et al. 2007, 

 Montgomery County Montgomery County DEP

Biodiversity 

% cover of exotic herbaceous species NPS I&M Schmit and Campbell 2007, 2008

Exotic tree/shrub density NPS I&M Schmit and Campbell 2007, 2008

Presence of forest pest species NPS I&M Schmit and Campbell 2007, 2008

Native seedling regeneration NPS I&M Schmit and Campbell 2007, 2008

Fish index biological integrity (FIBI) NPS I&M Hilderbrand et al. 2007,

 Montgomery County Montgomery County DEP

Prop. of area occupied (PAO) by amphibians NPS I&M Mattfeldt et al. 2008

Presence of forest interior dwelling species D.C. Birdscape II, Hadidian et al. 1997, 

 (FIDS) of birds NPS I&M Dawson and Efford 2006

Deer density NPS I&M Bates 2007

Ecosystem Pattern and Processes 

Proportion forest cover (within park) UMCES; NPS Townsend et al. 2006

Prop. impervious surface (within park) UMCES; NPS Townsend et al. 2006

Critical connectivity (Dcrit; within park) UMCES; NPS Townsend et al. 2006

Prop. forest cover (within park) + 5X buffer UMCES; NPS Townsend et al. 2006

Prop. imperv. surface (within park) + 5X buffer UMCES; NPS Townsend et al. 2006

Critical connectivity (within park) + 5X buffer UMCES; NPS Townsend et al. 2006
71

CHAPTER 5: RESOURCE CONDITION ASSESSMENT

ASSESSMENT

Habitat framework

To ensure assessments were broadbased, metrics from at least two 

categories from the ecological 

monitoring framework (Air Quality, 

Water Quality, Biodiversity, and 

Ecosystem Pattern and Processes) 

were included in the assessment of 

each habitat (Table 5.4). The data 

used range from 2000 to 2008, with 

data density ranging from one park 

assessment at one time (impervious 

surface, critical connectivity) through 

to 241 measurements monthly from 

13 sites (dissolved oxygen) (Table 5.4). 

The data set was a subset of that 

used for the ecological monitoring 

framework, so the sources of all data 

are presented in Table 5.3 and the 

threshold justifi cations are presented 

in Chapter 4, Metrics & Thresholds. 

Justifi cation for the inclusion of 

metrics as relevant to a particular 

habitat assessment is provided below. 

Forest Habitat

The majority of indicators 

used to assess ecosystem 

condition of forest 

habitats were measures 

of Biodiversity (fi ve), with two 

indicators of Ecosystem Pattern 

and Processes (Table 5.4). Of the 

seven indicators, three are relevant 

to the measurement of the quality 

of a resource within forest habitats 

(presence of forest interior dwelling 

birds, native seedling regeneration, 

critical connectivity), while the 

remaining four (exotic tree/shrub 

density, presence of pest species, 

deer density, impervious surface) 

measure the scale of stressors that 

are likely to directly impact forest 

habitats (Table 5.4). 

Wetland (Inland) Habitat

Six of the seven indicators 

used to assess condition 

of wetland habitats 

were Water Quality indicators: 

three indicators of stressors (total 

phosphorus, salinity, aqueous nitrate) 

and three indicators of habitat 

quality for aquatic fauna (dissolved 

oxygen, benthic IBI, physical habitat 

index; Table 5.4). The remaining 

indicator (proportion of area 

occupied by adult amphibians) is a 

measure of Biodiversity and provides 

information regarding the ecosystem 

resource value of the habitat (Table 

5.4).

Artifi cial-terrestrial Habitat

Assessment of artifi cialterrestrial habitats 

condition was based 

on indicators in three 

categories: Biodiversity (deer 

density), Ecosystem Pattern and 

Processes (impervious surface), and 

Air Quality (soot, ozone, sulfate 

deposition, nitrate deposition, 

mercury deposition) (Table 5.4). 

Recognizing that Air Quality

indicators could be used for any 

habitat, particularly any terrestrial 

habitat, they were considered 

especially appropriate for use in 

the predominantly mown grass 

characterizing artifi cial-terrestrial 

habitat within Rock Creek Park. 

These open vistas rely most heavily 

on the resource of high visibility. 

The impacts to plant health by 

high ozone are not well studied for 

artifi cial habitats, though exposure 

to atmospheric deposition is likely 

greater due to decreased foliar 

interception. Wet deposition of 

sulfate, nitrate, and mercury is more 

likely to have a negative impact in 

open areas where transport rate 

to groundwater and creeks will be 

greater than areas such as forest 

where more rainfall is intercepted 

by plant canopies and where there 

is greater plant biomass above and 

below ground to re-absorb nutrients 

from soils.
72

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

72

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Calculation of natural 

resource condition

Ecological monitoring categories

All data were collected between 

2000 and 2008. However, due to 

the number of sampling sites (or 

spatial scale of measurement) and 

sampling frequency (monthly to 

annual), the amount of information 

used to characterize park resources 

(data density) varied from 1 (e.g., 

Table 5.4. Summary of data used in Rock Creek Park habitat-based natural resource condition assessment.

Metric (by habitat) Threshold Sites Samples Period

Forest 

Exotic tree/shrub density < 5% (of total basal area) 3 4 2006-2007

Presence of forest pest species < 1% of trees infested 3 3 2005-2007

Presence of forest interior dwelling species > 1 ‘highly sensitive’ FIDS

(FIDS) of birds > 4 ‘sensitive’ FIDS park 3 2003-2008

Deer density Forest: < 8 deer km-2 park 8 2000-2007

Native seedling regeneration > 31,875 seedlings ha-1 5 5 2006-2007

Critical connectivity (Dcrit; within park) < 360 m park 1 2001-2002

Prop. impervious surface (within park) < 0.1 park 1 2000

Wetland (Inland) 

Total phosphorus < 36.56 μg L-1 13 230 2005-2007

Salinity < 0.25 13 219 2005-2007

Aqueous nitrate < 2 mg L-1 13 234 2005-2007

Dissolved oxygen June 1-Jan 31:  3.2 mg L-1

 Feb 1-May 31:  5.0 mg L-1 13 241 2005-2007

Benthic Index Biological Integrity (BIBI) > 3 6 6 2000-2004

Prop. of area occupied (PAO) by amphibians 20% < PAO < 80% each spp. park 9 2005-2007

Physical habitat index (PHI) > 42 3 8 2000-2004

Artifi cial-terrestrial 

Deer density Grassland: < 20 deer km-2 park 8 2000-2007

Prop. impervious surface (within park) < 0.1 park 1 2000

Particulate matter (soot; PM2.5) concentration < 15 mg m3

 3 15 2000-2004

Ozone < 0.075 ppm 2 8 2000-2003

Wet SO4

 deposition < 10 kg ha-1 yr-1 3 10 2000-2007

Total NO3

-

 deposition (other) < 10 kg ha-1 yr-1 3 10 2000-2007

Hg deposition < 2 ng L-1 1 86 2004-2006

assessment of impervious surface 

within the park) to 242 (water 

temperature) during the eightyear period (Table 5.2). These data 

were compared to threshold values 

(Chapter 4, Metrics & Thresholds), 

as a percentage of measurements 

attaining the threshold value for 

each metric, where a value of 1.0 

indicated that all sites and times 

met the threshold to maintain 

natural resources, and a value 

of 0.0 indicated that no sites 
73

CHAPTER 5: RESOURCE CONDITION ASSESSMENT

NPS

ASSESSMENT

at any sampling time met the 

threshold value. As there were two 

thresholds determined for total 

NO3

-

 deposition—one for forest and 

one for cultivated lands—an areaweighted mean was used to calculate 

just one score for total NO3

-

. For 

determination of status of metrics 

and metric categories, percentage 

attainment scores were categorized 

on a scale from very good to very 

degraded (Table 5.5). 

Habitats

For each individual metric, the 

percent attainment of the threshold 

value was calculated as described for 

ecological monitoring categories. For 

determination of status of metrics 

and habitats, percentage attainment 

scores were categorized on a scale 

from very good to very degraded 

(Table 5.6).

Use of habitat framework for 

calculating sub-park assessments

In consultation with NPS staff, 

Rock Creek Park was divided into 

sub-regions of potential interest 

to management. The 10 regions 

were based largely on physical 

divisions within the park caused by 

Rock Creek itself as well as major 

roads (Figure 5.3). Monitoring data 

were not available to provide a 

direct natural resource condition 

assessment between these park 

sub-regions; however, the habitat 

assessment framework was used to 

provide an indication of sub-region 

condition assessments within the 

park, based upon habitat occurrence 

within each sub-region (Table 5.8). 

The underlying assumption was 

that condition of each habitat was 

uniform across the park. After 

calculating the area of the three 

habitats within each sub-region, 

overall habitat attainment values 

Table 5.5. Categorical ranking of threshold attainment categories.

Measured attainment of thresholds Natural resource condition

81-100% Very good

61-80% Good

41-60% Fair

21-40% Degraded

0-20% Very degraded

Figure 5.3. Defi ned 

management based 

sub-regions within 

Rock Creek Park. 

(Table 5.7) were used to calculate a 

habitat area-weighted mean for each 

of the 10 sub-regions within the park 

(Table 5.8). 

Base-fl ow sampling 

off the bridge at 

Rock Creek and Joyce 

Road.

USGS

1

2

3

4

5 6

7

8

10

9
74

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

74

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Results

Ecological monitoring framework

Within the ecological monitoring 

framework, the metric scores ranged 

from 0 (very degraded) to 100% (very 

good) attainment of threshold values 

(Table 5.5). The overall condition of 

Rock Creek Park, based on attainment 

of ecological threshold for 29 metrics, 

was assessed as fair. 

Air Quality

Air Quality for Rock Creek 

Park was generally in 

degraded condition (Table 

5.6). Total NO3

-

 deposition 

was in very good condition (89% 

attainment), particulate matter (soot; 

PM2.5) was in degraded condition 

(27% attainment), and ozone, wet SO4

deposition, and mercury deposition 

were all in very degraded condition 

(all 0% attainment). While most 

metrics had a mean value similar to 

the threshold value, mean mercury 

deposition (13.5 ng L-1) was an order of 

magnitude higher than the threshold 

value (2 ng L-1) (Tables 5.2, 5.6). 

Water Quality

Water Quality for Rock 

Creek Park was very 

variable between metrics 

(Table 5.6). Of the nine 

metrics, fi ve were in very good 

condition (pH 93%, dissolved oxygen 

87%, water temperature 100%, acid 

neutralizing capacity 100%, physical 

habitat index 100%), aqueous nitrate 

was in fair condition (46%), salinity 

in degraded condition (30%), and 

two metrics were in very degraded 

condition (total phosphorus 0%; 

benthic IBI 0%; Table 5.6). Total 

phosphorus was notable, with a mean 

concentration (929 μg L-1) that was an 

order of magnitude higher than the 

threshold value (36.56 μg L-1; Tables 

5.2, 5.6). 

Biodiversity

Biodiversity for Rock Creek 

Park was assessed to be 

in a fair condition (Table 

5.6). High numbers of 

observed forest interior dwelling bird 

species and lack of forest pest species 

resulted in very good conditions for 

these metrics (100% attainment). 

Proportion of area occupied by adult 

amphibians was assessed as good/very 

good condition (78% attainment) 

and the limited presence of exotic 

trees and shrubs resulted in a good 

assessment (70%). Higher abundance 

of exotic herbaceous species indicates 

degraded/fair condition (40%) and 

low fi sh IBI, high deer density, and 

low native seedling regeneration 

(17%, 2%, 0% attainment 

respectively) indicated very degraded 

condition for these metrics (Table 

5.6). High mean percent cover of 

invasive exotic species but moderate 

to high attainment of the threshold 

suggests that when invasive exotic 

species are present, abundance is 

high (Table 5.6). The well-established 

forest threshold for deer density 

(8 deer km-2) is well below the 

measured mean density for Rock 

Creek Park of 26 deer km-2 and the 

mean native seedling regeneration of 

6,000 seedlings ha-1 was well below 

the threshold density for forest 

maintenance (35,000 seedlings ha-1) 

(Tables 5.2, 5.6). 

Ecosystem Pattern and 

Processes

Ecosystem Pattern and 

Processes within Rock 

Creek Park were overall in 

a good condition (Table 5.6). Two of 

the park plus fi ve times buffer metrics 

had 0% attainment (forest cover, 

impervious surface) and one received 

100% (critical connectivity). The three 

interior park metrics achieved 100% 

attainment (forest cover, critical 

connectivity, impervious surface). 
75

CHAPTER 5: RESOURCE CONDITION ASSESSMENT

ASSESSMENT

Table 5.6. Summary natural resource condition assessment for Rock Creek Park by metric categories. 

Categories and Metrics Mean

(refer to Chapter 4)

Condition

% attainment Assessment 

Air Quality

Ozone 0.09 ppm 0 Very degraded

Total NO3

-

 deposition (forest habitat) 10.8 kg ha-1 yr-1

90 

Very good

Total NO3

-

 deposition (cultivated) 10.8 kg ha-1 yr-1

Wet SO4 deposition 18.2 kg ha-1 yr-1 0 Very degraded

Particulate matter (soot; PM2.5) concentration 14.4 mg m-3 27 Degraded

Hg deposition 13.5 ng L-1 0 Very degraded

Water Quality

pH 7.8 93 Very good

Dissolved oxygen 7.5 mg L-1 87 Very good

Water temperature 13.5 oC 100 Very good

Acid neutralizing capacity (ANC) 1597 μeq L-1 100 Very good

Salinity 0.4 30 Degraded

Aqueous nitrate 2.6 mg L-1 46 Fair

Total phosphorus 929 μg L-1 0 Very degraded

Benthic index biological integrity (BIBI) 1.5 0 Very degraded

Physical habitat index (PHI) 56.2 100 Very good

Biodiversity

% cover of exotic herbaceous species 20.5% 40 Degraded/Fair

Exotic tree/shrub density 16.7% 70 Good

Presence of forest pest species 0% 100 Very good

Native seedling regeneration 6,000 seedlings ha-1 0 Very degraded

Fish index biological integrity (FIBI) 2.5 17 Very degraded

Prop. of area occupied (PAO) by amphibians 53.4% 78 Good

Presence of forest interior dwelling species

(FIDS) of birds

2.3 ‘highly sensitive’ 

7 ‘sensitive’ 100 Very good

Deer density (forest 1421 acres)

Deer density (grassland 298 acres) 26.4 deer km-2 2 Very degraded

Ecosystem Pattern and Processes

Proportion forest cover (within park) 0.71 100 Very good

Prop. impervious surface (within park) 0.05 100 Very good

Critical connectivity (Dcrit; within park) 340 m 100 Very good

Prop. forest cover (within park) + 5X buffer 0.24 0 Very degraded

Prop. imperv. surface (within park) + 5X buffer 0.45 0 Very degraded

Critical connectivity (within park) + 5X buffer 270 m 100 Very good

NB: Total NO3

-

 deposition forest attainment 100%, cultivated attainment 40%, area-weighted park total 89.6% attainment; Deer density forest

attainment 0%, grassland attainment 12.5%, area-weighted park attainment 2.2%.

}

}
76

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

76

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table 5.7. Summary of Rock Creek Park habitat-based natural resource condition assessment.

Metric (by habitat) Mean

(refer to Chapter 4)

Condition

% attainment Assessment

Forest: 1421 acres (81%)

Exotic tree/shrub density 16.7% 70 Good

Presence of forest pest species 0% 100 Very good

Presence of forest interior dwelling species 

(FIDS) of birds

2.4 ‘highly sensitive’ 

7.8 ‘sensitive’ 100 Very good

Deer density 26.4 deer km-2 0 Very degraded

Native seedling regeneration 6,000 seedlings ha-1 0 Very degraded

Critical connectivity (Dcrit; within park) 340 m 100 Very good

Prop. impervious surface (within park) 0.05 100 Very good

Wetland (Inland): 35 acres (2%)

Total phosphorus 929 μg L-1 0 Very degraded

Salinity 0.4 30 Degraded

Aqueous nitrate 2.6 mg L-1 46 Fair

Dissolved oxygen 7.5 mg L-1 87 Very good

Benthic index biological integrity (IBI) 1.5 0 Very degraded

Prop. of area occupied (PAO) by amphibians 53.4% 78 Good

Physical habitat index (PHI) 56.8 100 Very good

Artifi cial-terrestrial: 298 acres (17%)

Deer density 26.4 deer km-2 12 Very degraded

Prop. impervious surface (within park) 0.05 100 Very good

Particulate matter (soot; PM2.5) concentration 14.4 mg m-3 27 Degraded

Ozone 0.09 ppm 0 Very degraded

Wet SO4

 deposition 18.2 kg ha-1 yr-1 0 Very degraded

Total NO3

-

 deposition (cultivated) 10.8 kg ha-1 yr-1 40 Degraded/Fair

Hg deposition 13.5 ng L-1 0 Very degraded

Habitat Framework

Within the habitat assessment 

framework, the metric scores ranged 

from 0 (very degraded) to 100% (very 

good) attainment of threshold values 

(Table 5.7). The overall condition of 

Rock Creek Park was assessed as fair 

(Table 5.7, Figure 5.4). 

Forest Habitat

Forest Habitat within Rock 

Creek Park was assessed 

to be in good condition 

(Table 5.7, Figure 5.4). These habitats 

have high deer populations (0% 

attainment) and low native seedling 

regeneration (0% attainment). 

However, low percentage of 

impervious surface and high forest 

patch connectivity (100% attainment 

within the park), together with low 

forest pest species, low presence 

of exotic trees and shrubs (70% 

attainment), as well as diverse forest 

interior dwelling bird species (100% 

attainment) result in the good 

assessment (Table 5.7). 
77

CHAPTER 5: RESOURCE CONDITION ASSESSMENT

ASSESSMENT

Figure 5.4. Summary 

results of habitatbased Rock Creek 

Park natural resource 

condition assessment.

Wetland (Inland) Habitat

Wetland Habitat within 

Rock Creek Park was 

assessed to be in fair 

condition (Table 5.7, Figure 

5.4). These habitats have high total 

phosphorus concentrations (0% 

attainment), low benthic index of 

biotic integrity (0% attainment), 

high salinity (30% attainment) and 

high nitrate concentration (46% 

attainment), but they also have high 

dissolved oxygen (87% attainment), 

physical habitat index (100% 

attainment), and attainment of the 

proportion of area occupied by adult 

amphibians (78%; Table 5.7, Figure 

5.4). 

Artifi cial-terrestrial Habitat

Artifi cial-terrestrial Habitat

within Rock Creek Park was 

assessed to be in degraded 

condition (Table 5.7, Figure 

5.4). Though these habitats have low 

percentage of impervious surface 

within the park (100% attainment), 

they are in degraded conditions 

for NO3

-

 (40% attainment) and soot 

deposition (PM2.5; 27% attainment), 

and in highly degraded conditions 

for deer density (12.5% attainment), 

ozone concentration, wet SO4 

deposition, and mercury deposition 

(all 0% attainment; Table 5.7, Figure 

5.4).

FOREST WETLAND (INLAND) ARTIFICIAL-TERRESTRIAL

Rock Creek Park artificial-terrestrial 

habitats have high particulate matter 

or soot (low visibility) and low 

impervious surface , but high 

deer populations , high ozone 

levels , fair sulfate deposition 

and high nitrate and mercury 

deposition .

Rock Creek Park wetland habitats have 

intact, shady stream banks , 

high nutrients , salinity , 

and oxygen levels with stable 

populations of amphibians , but 

degraded populations of benthic 

invertebrates .

Rock Creek Park forest habitats have 

moderate numbers of exotic shrubs 

and trees , low percentage of 

impervious surface , and large 

deer populations . Native 

seedling regeneration is low, but 

bird species diversity is high in 

continuous forest with low 

occurence of insect pests .

 

Habitat-based natural resource condition assessment of Rock Creek Park

GOOD FAIR DEGRADED

FAIR / GOOD

PERCENT ATTAINMENT:

HABITAT CONDITION: DEGRADED

20-40%

VERY

DEGRADED

0-20%

FAIR

40-60%

GOOD

60-80% 80-100%

VERY

GOOD

Legend
78

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

78

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Assessment of park sub-regions

Using habitats within each park subregion (Figure 5.3) to assess resource 

condition resulted in a range from 

46.6% attainment in region six (east 

central) up to 60.0% attainment in 

region one (northern-most subregion), which resulted in all subregions assessed as being in fair 

condition (Table 5.8). Forest habitat 

dominates all sub-regions, with 

the exception of region six, which 

also contains signifi cant artifi cialterrestrial habitat (39% of total area; 

Table 5.8). 

Table 5.8. Habitat-based natural resource condition assessment within sub-regions of Rock Creek Park.

Habitat Threshold

attainment

Area of each park sub-region (Figure 5.3), divided by habitat type (acres)

1 2 3 4 5 6 7 8 9 10

Forest 67% 44.2 127.1 258.2 147.4 135.8 119.3 348.8 174.3 57.3 132.7

Wetland 

(Inland) 49% 0.3 4.6 0.7 5.4 0.5 7.6 2.6 12.0 2.4 3.9

Artifi cialterrestrial 26% 0.8 4.5 18.2 12.6 13.9 80.7 31.5 16.6 9.2 14.7

Habitat area-weighted 

sub-region attainment (%) 66 65 64 63 63 50 64 63 61 63

Sub-region condition Good Good Good Good Good Fair Good Good Good Good

Discussion

Using two different frameworks 

based upon ecological monitoring 

categories and dominant habitat 

types, natural resource condition 

within Rock Creek Park was assessed 

as being in fair to good condition 

(Figure 5.4, Tables 5.6 and 5.7). Air 

Quality and Artifi cial-terrestrial 

Habitat were assessed to be in 

degraded condition, however, Water 

Quality, Ecosystem Pattern and 

Processes, and Forest Habitat were 

assessed to be in good condition. 

Ecological monitoring framework

Air Quality within Rock Creek 

Park was overall in a degraded 

condition refl ecting regional and 

local trends. Water Quality was in 

good condition, however, it was 

compromised by high nutrient and 

salinity concentrations and very 

degraded benthic communities 

(Table 5.6). Species abundance in 

macroinvertebrate communities has 

been found to be negatively correlated 

with concentrations of both nitrogen 

and phosphorus (Wiegel and Robertson 

2007). The same study found a distinct 

break point or threshold in benthic 

species between 64 μg L-1 and 150 μg L-1

total phosphorus, which is similar to 

the threshold used in this assessment 

This green luna 

moth (Actias luna), 

resting in the hand 

of Smithsonian’s 

National Museum 

of Natural History 

entomologist Gary 

Hevel, was one of 

the more than 665 

species identifi ed 

during a 24-hour 

BioBlitz held in Rock 

Creek Park in the 

spring of 2007.

Mark Thiessen, National Geographic Society
79

(36.56 μg L-1) and is well below the 

mean of all samples reported for 

Rock Creek Park, 929 μg L-1 (Table

5.6). Biodiversity was in fair 

condition, partially resulting from 

the degraded condition of fi sh 

communities which have been found 

to be highly negatively correlated 

with nutrient concentration (Wiegel 

and Robertson 2007), and degraded 

stream condition in general (Roth et 

al. 2000). Many studies have shown 

that high deer densities can inhibit 

the development and regeneration 

of understory species (Healy 1997, 

Decalesta and Stout 1997, Horsley et 

al. 2003). Mean deer densities over 

25 deer km-2 are therefore likely to 

be one of the causes of the degraded 

native seedling regeneration (Table 

5.6). While forest dwelling bird 

species met the threshold condition, 

long term data sets collected within 

the park show that the park is 

consistent with a regional pattern 

of large reductions in total number 

as well as number of species of 

long distance migratory songbirds 

(Terborgh 1992). Ecosystem Pattern 

and Processes were in overall 

good condition, with a clear trend 

between very good conditions (high 

forest cover, good patch connectivity, 

and low impervious surface) within 

the park boundaries, however, 

rapid reduction of forest cover and 

an increase in impervious surface 

directly surrounds the park (Table 

5.6). 

Habitat framework

Forest Habitat was assessed as being 

in good condition with relatively 

diverse forest interior dwelling bird 

species, forest connectivity, low 

presence of pest species, and low 

percentage impervious surface within 

the park. High deer abundance, 

low native seedling regeneration, 

and presence of exotic tree and 

shrub species are compromising 

the resource condition of forest 

habitats. Wetland (Inland) Habitat is 

in fair condition, refl ecting the high 

stream water nutrients and salinity, 

and degraded benthic invertebrate 

communities. Artifi cial-terrestrial 

Habitat is most impacted by poor air 

quality, but also by high deer density. 

Comparison of approaches

Both frameworks resulted in very 

similar overall assessments of 

resource condition within Rock Creek 

Park. The benefi t of the habitat 

framework is the strong linkage 

between habitat types, metrics, and 

the desired and degraded condition 

of each represented habitat, with a 

data-based assessment approach to 

track condition. 

Data gaps

While it was possible to assess all 

habitat types within Rock Creek Park, 

it is recognized that limited data 

is available for seeps and springs 

within the park, and this is seen as a 

signifi cant data gap. These important 

and regionally vulnerable resources 

could not be included in the current 

assessment, but would ideally be 

included within assessment of 

Wetland (Inland) Habitat. 

Literature cited (Chapter 5)

Bates, S. 2007. National Capital Region 

Network 2006 Deer Monitoring Report. 

National Park Service, Fort Collins, CO. 

NPS/NCRN/ NRTR—2007/033.

Bricker, S.B., B. Longstaff, W. Dennison, 

A. Jones, K. Boicourt, C. Wicks, and 

J. Woerner. 2008. Effects of nutrient 

enrichment in the nation’s estuaries: 

A decade of change. Harmful Algae 8: 

21-32.

CHAPTER 5: RESOURCE CONDITION ASSESSMENT

ASSESSMENT
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Brooks, R.P., T.J. O’Connell, D.H. Wardrop, 

and L.E. Jackson. 1998. Towards a 

regional index of biological integrity: 

The example of forested riparian 

ecosystems. Environmental Monitoring 

and Assessment 51: 131-143.

Carter, S.L., G. Mora-Bourgeois, T.R. 

Lookingbill, T.J.B. Carruthers, and 

W.C. Dennison. 2007. The challenge 

of communicating monitoring results 

to effect change. The George Wright 

Forum 24(2): 48-58.

Dawson, D.K. and M.G. Efford. 2006. 

National Capital Region Network – 

Protocol for Monitoring Forest-Nesting 

Birds in National Park Service Parks.

DeCalesta, D.S. and S.L. Stout. 1997. 

Relative deer density and sustainability: 

Conceptual framework for integrating 

deer management with ecosystem 

management. Wildlife Society Bulletin 

25(2): 252-258.

Dennison, W.C., T.R. Lookingbill, T.J.B 

Carruthers, J.M. Hawkey, and S.L. 

Carter. 2007. An eye-opening approach 

to developing and communicating 

integrated environmental assessments. 

Frontiers in Ecology and the 

Environment 5(6): 307-314.

Ding, Y., W. Wang, X. Cheng, and 

S. Zhao. 2008. Ecosystem health 

assessment in inner Mongolia region 

based on remote sensing and GIS. 

The International Archives of the 

Photogrammetry, Remote Sensing and 

Spatial Information Sciences XXXVII 

(B1): 1029-1034.

Fancy, S.G., J.E. Gross, and S.L. Carter. 

2008. Monitoring the condition of 

natural resources in US national 

parks. Environmental Monitoring and 

Assessment: Electronically published 

May 29, 2008. 

Ferreira, J.G. 2000. Development of an 

estuarine quality index based on key 

physical and biogeochemical features. 

Ocean and Coastal Management 43: 

99-122.

Hadidian, J., J. Saver, C. Swarth, P. Handly, 

S. Droege, C. Williams, J. Huff, and G. 

Didden. 1997. A citywide breeding bird 

survey for Washington, D.C. Urban 

Ecosystems 1: 87-102.

Harrison, T.D. and A.K. Whitfi eld. 2004. 

A multi-metric fi sh index to assess the 

environmental condition of estuaries. 

Journal of Fish Biology 65: 683-710.

Healy, B. 1997. Long-term changes 

in a brackish lagoon, Lady’s Island 

Lake, Southeast Ireland. Biology and 

Environment: Proceedings of the Royal 

Institute Academy 97B(1): 33-51.

Hilderbrand, R.H., R. Raesly, and D. 

Boward. 2007. National Capital Region 

Network Biological Stream Survey 

Protocols.

Horsley, S.B., S.L. Stout, and D.S. 

DeCalesta. 2003. White-tailed deer 

impact on the vegetation dynamics of 

a northern hardwood forest. Ecological 

Applications 13(1): 98-118.

IUCN. 2007. Habitats classifi cation 

scheme (version 3.0). International 

Union for the Conservation of Nature. 

http://www.iucnredlist.org/static/

major_habitats.

Karr, J.R. 1981. Assessment of biotic 

integrity using fi sh communities. 

Fisheries 6(6): 21-27.

Kiddon, J.A., J.F. Paul, H.W. Buffum, C.S. 

Strobel, S.S. Hale, D. Cobb, and B.S. 

Brown. 2003. Ecological condition 

of US Mid-Atlantic estuaries, 1997-

1998. Marine Pollution Bulletin 46: 

1224-1244.
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Mattfeldt, S. D., E. H. Grant, and L. L. 

Bailey. 2008. Amphibian Monitoring in 

the National Capital Region: A focus 

on lentic and lotic habitats. NPS, NCRN. 

NPS/NRTR/NCRN—2008/088.

Norris, M., J.P. Schmit, and J. Pieper. 2007. 

National Capital Region Network 

2005–2006 Water Resources Monitoring 

Report. Natural Resource Program 

Center, Fort Collins, CO. NPS/NCRN/

NRTR—2007/066.

Pantus, F.J. and W.C. Dennison. 2005. 

Quantifying and evaluating ecosystem 

health: A case study from Moreton Bay, 

Australia. Environmental Management 

36: 757-771.

Roth, N., M. Southerland, J. Chaillou, 

R. Klauda, P. Kazyak, S. Stranko, S. 

Weisberg, L. Hall Jr, and R. Morgan. 

1998. Maryland biological stream 

survey: Development of a fi sh index 

of biotic integrity. Environmental 

Monitoring and Assessment 51: 89-106.

Roth, N.E., M.T. Southerland, J.C. 

Chaillou, P.F. Kazyak, and S.A Stanko. 

2000. Refi nement and validation 

of a fi sh index of biotic integrity 

for Maryland streams. Chesapeake 

Bay and Watershed Programs: 

Monitoring and non-tidal assessment 

CBWP-MANTA-EA-00.

Schmit, J.P. and J.P. Campbell. 2007. 

National Capital Region Network 2006 

Forest Vegetation Monitoring Report. 

NPS. NPS/NCRN/NRTR-2007/046.

Schmit, J.P. and J.P. Campbell. 2008. 

National Capital Region Network 2007 

Forest Vegetation Monitoring Report. 

NPS, Fort Collins, CO. NPS/NCRN/

NRTR—2008/125.

Terborgh, J. 1992. Why American 

songbirds are vanishing. Scientifi c 

American 266: 98-104.

Townsend, P.A., R.H. Gardner, T.R. 

Lookingbill, and C.C. Kingdom. 2006. 

National Capital Region Network—

Remote Sensing and Landscape Patter 

Protocol for Long-Term Monitoring of 

Parks.

U.S. EPA. 2000. Mid-Atlantic 

Highland Streams Assessment. 

U.S. Environmental Protection 

Agency Region 3. Philadelphia, PA. 

EPA/903/R-00/015. 

U.S. EPA. 2002. A Framework for 

Assessing and Reporting on 

Ecological Condition: an SAB Report. 

Environmental Protection Agency. 

Science Advisory Board. Washington, 

D.C. EPA-SAB-EPEC-02-009. 

Wazniak, C.E., M.R. Hall, T.J.B. Carruthers, 

B. Sturgis, W.C. Dennison, and R.J. Orth. 

2007. Linking water quality to living 

resources in a mid-Atlantic lagoon 

system, USA. Ecological Applications 

17(5):S64-S78.

Weigel, B.M. and D.M. Robertson. 2007. 

Identifying biotic integrity and water 

chemistry relations in nonwadable 

rivers of Wisconsin: Toward the 

development of nutrient criteria. 

Environmental Management 40: 

691-708.

Williams, M., B. Longstaff, C. Buchanan, 

R. Llanso, and W. Dennison. In press. 

Development and evaluation of a 

spatially-explicit index of Chesapeake 

Bay health. Marine Pollution Bulletin.

CHAPTER 5: RESOURCE CONDITION ASSESSMENT

ASSESSMENT
82

Simon Tan

American redstart (Setophaga ruticilla), a highly sensitive bird species sometimes found in Rock Creek Park.

ROCK CREEK PARK: NATIONAL RESOURCE CONDITION ASSESSMENT
83

Community

Community

Implementation

Evaluation

Planning

Conceptualization

Communication

Environment

Friends of Rock Creek’s

Rock Creek 

Park

Chapter 6: Implications

Use of natural resource 

condition assessment in an 

adaptive management cycle

The approach taken in this natural 

resource condition assessment was 

to survey and compile available data 

for resources and stressors within 

Rock Creek Park (ROCR) (Chapters 

2 and 3), use available literature 

to develop thresholds for these 

metrics (Chapter 4) and then use an 

ecological monitoring framework 

(Inventory and Monitoring ‘Vital 

Signs’) as well as a newly developed 

habitat framework to assess the 

status of resources within Rock Creek 

Park (Chapter 5). The syntheses and 

assessment frameworks presented 

in this report have the potential to 

directly include monitoring data 

into a park adaptive management 

cycle of conceptualization, 

implementation, evaluation, and 

communication (Figure 6.1). The two 

assessment frameworks provide a 

conceptualization (Figure 5.4, Table 

5.2) that can potentially assist in 

the planning and prioritization of 

management action implementation. 

The synthetic condition reporting 

(Figure 5.4, Table 5.7) provides 

an evaluation of current status 

assessment, based upon available 

data, and is presented as a snapshot 

for the park resource condition 

during the current 2000 decade (see 

Tables 5.2 and 5.4 for data used in 

assessment). Within Rock Creek Park, 

the developed conceptual framework 

can also be used to assess the 

effectiveness of the implementation 

of management strategies over the 

decadal time scale (Figure 6.1). Rock 

Creek Park is at the downstream end 

of a large urban watershed, such 

that engagement of community 

organizations (such as the Friends of 

Figure 6.1. Example 

of how the natural 

resource condition 

assessment 

framework can 

be applied to 

the adaptive 

management 

cycle within Rock 

Creek Park and in 

association with 

community partners.

IMPLICATIONS

In light of the assessment in Chapter 5, the data gaps, management recommendations, and 

guidelines on applying the assessment to an adaptive management cycle are identifi ed.
84

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

84

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Rock Creek’s Environment - FORCE) 

and communication of key ecological 

issues within the park to the public 

could be an important component 

of managing watershed stressors. 

The presented habitat frameworks 

(Figures 5.2 and 5.4, Table 5.7) 

summarize a diversity of complex 

data into a format conducive for 

communication to an audience of 

not only park resource managers, but 

also to the much broader audience 

of interested public. 

Use of the assessment 

framework to direct 

monitoring and decision 

making

One of the challenges or data 

gaps that became apparent in the 

process of synthesizing available 

data was the disparity between 

the scales of available data and the 

scales of required management 

questions or needs. During this 

assessment process, discussions with 

park resource managers identifi ed 

relevant sub-park geographic regions 

based upon physical structures 

(rivers and roads; Figure 5.3) and 

the habitat framework was used 

to provide initial overall ecosystem 

condition between these regions 

(Table 5.8). It is recognized, however, 

that this assessment could only be 

based upon the relative proportions 

of different habitat types within 

these regions and cannot be used 

to address the question of the 

resource condition of forest habitat 

between these ten park subregions. However, by identifi cation 

of relevant ecosystem metrics that 

are sensitive and measurable and 

by the development of relevant 

threshold values, the presented 

habitat assessment framework can 

be directly used to collect monitoring 

data to answer such a question. A 

once-off assessment of the seven 

metrics for a habitat (Figure 5.2) 

could be carried out between two 

relevant park sub-regions to quickly 

assess relative condition to directly 

inform management decisions. 

Implementation strategy for Rock Creek resource 

condition assessment

The habitat framework for 

assessment of resource condition 

within Rock Creek Park was used to 

summarize key fi ndings (stressors 

as well as features), ecological 

implications of these fi ndings and 

the recommended next steps to 

improve degraded features or 

maintain features currently in a 

desired condition (Table 6.1, Figure 

5.2). 

Forest Habitat

Within forest habitats, one 

of the largest challenges 

is overpopulation of deer, 

resulting in overgrazing of 

vegetation and limited regeneration 

of native seedlings as well as 

negative impacts upon diversity 

and abundance of forest interior 

FORCE

In April 2008, the 

Friends of Rock 

Creek’s Environment 

(FORCE) cleanup 

crew at Kensington 

Parkway in Chevy 

Chase piled up 

about 40 bags 

of trash. (Several 

more volunteers 

participated than this 

photo represents.)

FORCE
85

Table 6.1. Key fi ndings, implications, and recommendations resulting from Rock Creek natural resource condition assessment.

Key fi ndings by habitat Management implications Recommended next steps

FOREST

Deer overpopulation reducing

forest regeneration capacity 

•Increased herbivory reducing desired 

plant and bird species

•Implement deer population control 

measures

Presence of exotic plants •Displacement of native species, 

reducing biodiversity 

•Early detection

•Exotic control measures (spraying 

and mechanical)

•Prioritize control strategies

Intact forest within Rock Creek 

Park 

•Acts as a refuge for forest interior 

dwelling species of birds, amphibians 

•Minimize stressors (fi res, dumping)

•Minimize fragmentation (roads, 

structures and trails) 

WETLAND (INLAND)

Rock Creek and tributary 

streams have degraded water 

quality (phosphorus, nitrogen, 

salinity)

•Affects stream fl ora and fauna 

•Reduces quality of visitor experience

•Reduce point source nutrients within 

the park and watershed (partnerships 

with agencies)

•Road salt management

Stream benthic biota (IBI) 

regionally very poor, amphibian 

communities fair

•Reduced biodiversity

•Reduces support of higher trophic 

levels

•Improve water quality

Stream physical habitats vary 

from good to poor (monitoring 

sites currently limited)

•Maintains riparian habitat and in 

stream fauna (fi sh)

•protects park infrastructure (by 

limiting erosion)

•Identify priority tributaries and 

artifi cial drainage gullies for effective 

stormwater management

ARTIFICIAL-TERRESTRIAL

This habitat is poorly 

characterized

•These habitats are highly visible and 

heavily used by visitors

•Identify priority monitoring needs 

(soil compaction, invasive exotic 

species)

•Inventories (e.g. pollinator species)

Air quality severely 

compromised–least buffered in 

this habitat

•Human and ecosystem health 

impacted

•Regional partnerships and education 

to improve air quality

CHAPTER 6: IMPLICATIONS

dwelling bird species (Table 6.1). 

Large deer populations have also 

led to an increase in road collisions 

and for all these reasons it is 

recommended to implement deer 

population control measures to 

reduce the current population of 

over 26 deer km-2 (Table 5.7) to the 

threshold value for maintenance of 

healthy forest habitat, 8 deer km-2

(Table 4.3). Another challenge to 

forest habitats is the presence of 

exotic plants (including shrubs and 

trees) currently over 16% by area 

(Table 5.7) in monitored plots, well 

above the threshold of 5% cover 

(Table 4.3). Exotic plants can displace 

native species as well as reduce 

IMPLICATIONS
86

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

86

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

biodiversity, so it is recommended to 

emphasize early detection of these 

species, continue controlling these 

species when detected and clearly 

prioritize control strategies based 

on characteristics such as relative 

invasion and expansion rates of 

different species. Even considering 

these challenges, the forest within 

Rock Creek Park provides an 

important regional resource and 

supports regionally high (though 

potentially threatened) communities 

of forest interior dwelling bird 

species and amphibians due to the 

relatively large patches of connected 

and intact forest (Table 5.7). To 

maintain the ecosystem value of 

this forest, stressors such as fi res 

and dumping should be minimized 

where possible and maintenance 

of forest patches by minimizing 

further fragmentation due to roads, 

structures and trails should be 

encouraged. 

Wetland (Inland) Habitat

This assessment was 

based on data collected 

from Rock Creek and its 

tributaries (Figure 2.8) and 

indicates that the largest challenges 

are elevated nutrient concentrations 

and salinity (Table 5.7), resulting in 

negative impacts on stream fl ora 

and fauna and potential reduction 

of visitor experience (Table 6.1). It 

is recommended that road salting 

should be managed to further 

reduce impacts to streams and that 

nutrient reduction strategies should 

be implemented. In recognition 

of the location of Rock Creek Park 

downstream of a large urban 

watershed, it is recommended that 

nutrient reduction will require 

partnerships with local and regional 

agencies and organizations as well 

as a strong communication and 

education effort. The overall poor 

water quality is implicated in the 

regionally poor stream benthic biota 

(mean IBI value within the park of 

1.5, compared to an ideal value of 3 

(Tables 4.2 and 5.7), which indicates a 

reduction in biodiversity within these 

communities and a reduced ability to 

support higher trophic levels such as 

fi sh communities. It is recommended 

that reducing nutrients and salt 

inputs would assist in improving 

benthic communities (Table 4.2). 

Although the number of sampling 

sites was limited, stream physical 

habitat condition was reported to 

be generally good (Tables 4.2 and 

5.7), maintaining riparian habitat 

and providing potential habitat for 

fi sh species as well as assisting in 

protecting park infrastructure by 

limiting erosion. To maintain this 

important ecosystem feature, it is 

recommended to identify priority 

sites that may be susceptible to 

erosion and to implement stream 

bank stabilization where necessary. 

Finally, working with District of 

Columbia government agencies 

(DDOE–District Department Of 

Environment, DCWASA–D.C. Water 

And Sewer Authority, DDOT–District 

Department Of Transportation) 

is advised to address issues of 

stormwater quality and quantity, 

specifi cally stabilizing headwaters 

and addressing erosion and gully 

formation issues.

Artifi cial-terrestrial Habitat

The greatest challenge 

for this habitat is that 

the ecosystem status of 

this highly visible and 

highly utilized habitat is poorly 

characterized (Table 6.1). To improve 

future assessments as well as better 

identify management needs within 

this habitat, it is recommended 

to identify needs, implement 

monitoring such as soil compaction 

and invasive exotic species presence 

in these areas and develop 
87

inventories of some key insect 

species. Due to the limited covering 

vegetation, this habitat is the most 

susceptible to poor air quality effects 

on the ecosystem (fl ora and fauna) 

as well as human health. To address 

issues of degraded air quality, it 

is recommended that regional 

partnerships are further developed. 

It is suggested that Rock Creek 

Park could play an important role 

in public education about regional 

issues of poor air quality and about 

solutions to these challenges. 

Prioritizing identifi ed 

research needs based upon 

management data gaps

The ecological monitoring 

framework (Inventory and 

Monitoring ‘vital signs’ framework) 

was used to characterize data gaps, 

provide an ecological justifi cation 

and then suggest research needs to 

address the data gaps (Tables 5.2 and 

6.2). 

Air Quality (Tables 5.2 and 

5.3)

Although the direct effects 

of atmospheric pollutants 

upon fl ora and fauna are 

well established, one of the notable 

data gaps is a lack of data on the 

downstream impacts of sulfate and 

nitrate deposition upon artifi cialterrestrial habitats within the park. 

Research on these deposition effects 

is recommended (Table 6.2). Metrics 

measuring air quality show broad 

scale (1000s of miles) patterns, but 

they also show daily variability at 

small spatial scales. This variability 

leads to challenges scaling down 

from regional measurements to the 

assessment of specifi c air quality and 

air quality impacts within Rock Creek 

Park. Collaborations using park data 

to calibrate and validate air transport 

and deposition models could help 

to alleviate this data gap, as would 

gathering data along park roads to 

assess the impact of park traffi c on 

the air quality within Rock Creek 

Park. 

CHAPTER 6: IMPLICATIONS

A Rock Creek Park 

ranger demonstrates 

radio-tracking 

eastern box turtles 

for a group of young 

visitors.

NPS

IMPLICATIONS
88

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

88

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Data gaps

AIR QUALITY

Justifi cation Research needs

Ecological thresholds 

(atmosphere to water and 

meadow particularly) deposition 

(sulfate and nitrate)

•Deposition and ecosystem 

impacts as well as human 

(acid rain and fertilization)

•Habitat specifi c effects

•Deposition impacts, particularly meadow

Translating regional air data to 

park level

•Data regional but not 

downscaled to management 

unit

•Using transport and deposition models

•Calibrating with roadside data within the 

park

WATER QUALITY

Nutrient and salt sources are 

poorly defi ned both within and 

outside the park

•Need to know where to 

prioritize management 

actions

•Tracers, models and budgets needed (inside 

and outside the park)

•Identify all inputs (breaks, sanitary sewers)

Importance of riparian buffer 

and in-stream processing in 

controlling water quality; effects 

of increased storm fl ow on 

stream bank erosion

•How in-park management 

practices can protect and 

benefi t water resources

•In-stream processing capacity for nutrients

•Impacts of park operations on water 

quality, quantity and erosion rates

•Quantify bank erosion: Rock Creek and tribs

Groundwater inputs not well 

understood or quantifi ed

•Buried stream network •Seeps and spring characterization, 

groundwater monitoring and drainage 

delineation

What contaminants are in 

water and sediments and their 

ecological impacts

•Potential for 

bioaccumulation and legacy 

(long residence time)

•Contaminant inventory (personal care 

products etc.)

BIODIVERSITY

Relative importance of forest 

pests and exotic pests

•Early detection important 

for effective control

•Increase monitoring (particularly spatial)

Understanding forest 

regeneration dynamics (with 

signifi cant deer grazing)

•Intense herbivory prevents 

forest regeneration

•Intensive studies to examine rates of 

seedling regeneration (with and without 

grazing)

Biodiversity data lacking 

(invertebrate, amphibians in 

some habitats, mammals, fi sh, 

reptiles, FIDS, non-vascular and 

non-see vascular plants)

•Better understanding of 

what species are present 

and where

•Inventory and distribution maps

•Inventory and distribution of arthropods

ECOSYSTEM PATTERN AND 

PROCESSES

Local determination of 

ecological effects of forest 

connectivity

•Impacts population 

dynamics of plants and 

animals

•Ecologically relevant scales of dispersal (e.g. 

how large are faunal ranges, how far do 

seeds disperse)

Barriers to movement of invasion •Impacts population 

dynamics of plants and 

animals

•Documentation of existing barriers (e.g. 

roads, fi elds, playgrounds, trails), and 

investigation of how ‘hard’ they are.

Accounting of inner-basin 

(watershed) transfers

•Maintenance of water 

quality and quantity (i.e. 

reducing fl ows)

•Coordination amongst stakeholders and 

regional agencies.

Table 6.2. Data gaps and associated research needs resulting from Rock Creek natural resource condition assessment.

NB: FIDS – forest interior dwelling species of birds, and forest interior breeding species of birds
89

Water Quality (Tables 5.2 

and 5.3)

High nutrient and 

salt concentrations 

measured within the 

park have poorly defi ned sources, 

which is important for prioritizing 

management implementation (Table 

6.2). Better characterization of point 

source inputs, tracers to identify 

both point and diffuse sources 

of nutrients within the park and 

throughout the watershed, and the 

development of nutrient budgets 

and models would help identify 

and manage these inputs as well as 

communicate the needs for these 

actions. The streamside vegetation 

currently provides a reasonably intact 

buffer, but full characterization 

of streamside vegetation—and 

therefore the potential for within 

park nutrient processing—would 

be benefi cial, especially as the 

watershed becomes increasingly 

impervious, resulting in more rapid 

and greater volumes of runoff 

from surrounding urban areas. This 

challenge is exacerbated by the many 

buried streams surrounding the park 

and throughout the watershed. One 

major data gap is the quantifi cation 

of groundwater inputs and better 

characterization of the water quality 

and biotic integrity of the many 

seeps and springs within the park. 

Monitoring of nutrients and bacteria 

within these wetlands as well as 

in the tributaries of Rock Creek 

is recommended. Many potential 

pollutants and contaminants, such 

as personal care products, are not 

currently being assessed although 

some of these have potential for 

bioaccumulation and a long residence 

time within the environment. An 

inventory of these pollutants within 

the watershed, developed through 

collaborations with regional agencies 

and organizations, would address this 

data gap. 

Biodiversity (Tables 5.2 and 

5.3)

Forest pest species as 

well as invasive exotic 

species are known 

to be a challenge in the region 

and early detection is the best 

approach to effective control, so 

it is recommended to increase 

the spatial density of monitoring 

sites for pest species (Table 6.2). 

Deer overabundance is a key 

challenge for Rock Creek Park. 

To assist in maintaining the parks 

valuable forest habitat in the best 

possible ecological condition, a 

better understanding of forest 

regeneration under the currently 

high deer populations would be of 

great benefi t. Investigation of the 

potential benefi ts of deer exclusion 

areas may guide future management 

decisions as well as an understanding 

of the interaction of deer 

abundance, invasive exotic plants, 

and native seedling regeneration. 

For some key faunal communities 

such as invertebrates, amphibians 

in some habitats, and fi sh, there is a 

lack of biodiversity data (especially 

in forest areas and tributaries). Not 

only inventories, but distribution 

maps would assist in alleviating 

this data gap to better characterize 

and protect these communities. A 

more extensive characterization of 

forest interior dwelling species (FIDS) 

of birds would provide a clearer 

assessment of the sustainability of 

these populations. 

CHAPTER 6: IMPLICATIONS

IMPLICATIONS
90

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

90

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Ecosystem Pattern and 

Processes (Tables 5.2, 5.3)

Forest connectivity is 

important to maintain 

populations of both fauna 

and fl ora. There is currently limited 

local data available on the impacts 

of reduced forest connectivity, 

especially within an urban setting 

such as the forests of Rock Creek 

Park. Determination of dispersal 

distances for local species of plants 

and animals would greatly assist in 

putting a value on small patches 

of publicly-owned forest adjacent 

to Rock Creek Park (Table 6.2). 

Another signifi cant aspect to the 

maintenance of these faunal and 

fl oral populations is the presence 

of barriers to movement as these 

can reduce dispersal distance. 

Documentation of current and 

proposed barriers such as roads, 

fi elds, playgrounds and trails, as 

well as how much of a barrier 

these provide to different plant 

and animal species (how ‘hard’ 

they are), could therefore inform 

management decisions as to the 

ecological acceptability of different 

structures and developments. Rock 

Creek Park has reasonably intact 

stream banks and the largest area of 

forest within the watershed, which 

is likely to have a positive infl uence 

on water quality exiting the park 

and ultimately reaching the Potomac 

River and Chesapeake Bay. These 

effects are currently not quantifi ed, 

and synthetic assessments of water 

quality throughout the upper 

watershed are also not currently 

available. Coordination with 

stakeholders to provide watershed 

syntheses of water quality and some 

targeted data collection to assess 

water quality variation throughout 

the park would address this need.
91

Tom Paradis

Rock Creek Park wetland and forest habitats share space with urban roadways.

IMPLICATIONS
92

Ryan Valdez, DCNATURE.com

Boulder Bridge, Rock Creek Park.
93

Appendix A: Raw Data Used in Rock Creek Park

Natural Resource Condition Assessment

Site ID Year Total NO3

- Forest Habitat Cultivated habitat

MD99 2004 9.76 pass pass

MD99 2005 12.98 pass fail

MD99 2006 10.06 pass fail

MD99 2007 10.06 pass fail

MD03 2000 13.75 pass fail

MD03 2001 12.79 pass fail

VA10 2004 9.81 pass pass

VA10 2005 10.24 pass fail

VA10 2006 9.08 pass pass

VA10 2007 9.66 pass pass

Mean 10.82

SE 0.53

Table A.2. Total annual nitrate deposition (kg ha-1 yr-1). Thresholds are 15 for forest and 10 

for other habitats. 

Site ID Year Days

4th highest

daily max. 3-yr mean

MD25 1999 364 0.097

MD25 2000 364 0.094 0.093

MD25 2001 352 0.089 0.094

MD25 2002 362 0.098 0.089

MD25 2003 361 0.080 0.086

MD25 2004 365 0.081 -

MD43 1999 365 0.10

MD43 2000 366 0.08 0.094

MD43 2001 365 0.10 0.096

MD43 2002 365 0.11 0.095

MD43 2003 365 0.08 0.090

MD43 2004 366 0.08 .

Mean 0.090

SE 0.002

Table A.1. Ozone (ppm). Values that fail the threshold (0.075) are in bold.

appendix a
94

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

94

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Site ID Year Wet SO4

MD99 2004 15.10

MD99 2005 17.42

MD99 2006 18.92

MD99 2007 15.49

MD03 2000 18.90

MD03 2001 18.95

VA10 2004 17.38

VA10 2005 14.90

VA10 2006 15.52

VA10 2007 14.98

Mean 16.76

SE 0.55

Table A.3. Annual wet sulfate deposition (kg ha-1 yr-1). 

Values that fail the threshold (10) are in bold.

Site ID Year Mean

41 2000 17.02

41 2001 16.86

41 2002 15.79

41 2003 14.89

41 2004 15.01

42 2000 15.33

42 2001 15.05

42 2002 15.66

42 2003 13.51

42 2004 15.12

43 2000 15.39

43 2001 16.20

43 2002 16.05

43 2003 7.32

43 2004 7.37

Mean 14.44

SE 0.65

Table A.4. Particulate matter (soot; PM2.5 mg m-3). 

Values that fail the threshold (15) are in bold.

Year Count Mean

2004 25 14.07

2005 40 13.52

2006 21 12.91

Mean 13.50

SE 0.34

Table A.5. Annual Mean Hg Deposition (ng L-1). Values 

that fail threshold (2.0) are in bold.
95

Station DATE pH DO

(mg L-1)

Temp

(oC)

ANC

(μeq L-1)

Sal NO3

-

(mg L-1)

TP

(μg L-1)

BRBR 6/27/2005 7.9 7.2 21.3 1752 - 1.60 1.85

BRBR 10/4/2005 7.8 8.3 18.2 1280 - 1.80 1.33

BRBR 11/3/2005 7.8 7.6 10.6 1560 - 2.70 5.16

BRBR 12/8/2005 7.9 8.6 1.9 708 0.9 1.10 0.75

BRBR 1/3/2006 7.7 5.3 7.9 940 0.2 2.60 1.14

BRBR 2/14/2006 8.0 13.5 4.4 1712 1.2 1.30 0.14

BRBR 3/8/2006 8.9 9.0 5.7 1856 0.3 1.50 0.85

BRBR 4/4/2006 8.6 6.6 13.1 1448 0.3 1.10 -

BRBR 5/4/2006 8.5 2.6 16.9 1176 0.3 2.70 2.01

BRBR 6/1/2006 7.8 3.0 21.7 2256 0.3 3.00 2.08

BRBR 7/20/2006 8.0 7.5 24.1 1216 0.3 4.00 1.09

BRBR 8/3/2006 8.0 6.0 25.9 2144 0.4 4.30 1.93

BRBR 9/12/2006 7.6 8.8 18.0 2240 0.3 2.10 1.18

BRBR 10/11/2006 7.9 7.7 16.4 1896 0.3 3.80 1.14

BRBR 11/21/2006 8.1 10.1 7.3 3200 0.4 3.60 0.53

BRBR 12/21/2006 8.5 10.0 6.4 2048 0.4 - 1.41

BRBR 1/30/2007 0.0 14.0 1.4 2064 0.4 1.05 0.53

BRBR 3/19/2007 8.3 12.2 4.4 1984 0.4 1.61 0.17

BRBR 4/18/2007 8.6 12.9 9.8 1864 0.3 2.10 0.30

BRBR 5/22/2007 7.9 7.2 16.0 1328 0.4 1.93 0.45

BRBR 6/25/2007 7.9 7.3 20.8 2192 0.4 1.60 0.81

BRBR 7/30/2007 7.7 5.6 24.2 1544 0.2 0.60 0.63

BRBR 9/4/2007 8.6 9.5 22.0 2344 0.4 1.70 0.86

BRBR 10/11/2007 7.7 4.8 17.4 2248 0.3 2.00 0.81

BRBR 11/5/2007 8.1 9.1 9.5 2472 0.3 3.50 0.79

BRBR 12/3/2007 7.7 8.3 8.1 1360 0.1 1.80 1.57

DUOA 10/3/2007 7.8 7.8 18.3 1872 0.3 5.40 0.35

DUOA 11/1/2007 7.8 8.3 13.0 1904 0.3 4.40 0.47

DUOA 11/26/2007 7.8 8.8 9.9 1856 0.3 5.00 0.31

EGWA 6/27/2005 8.2 8.6 24.0 1264 - 1.00 1.25

EGWA 10/4/2005 8.0 6.0 19.2 1120 - 0.90 1.16

EGWA 11/3/2005 7.9 8.2 10.8 980 - 1.80 2.08

EGWA 12/8/2005 7.5 11.5 2.0 1220 1.0 0.60 -

EGWA 1/3/2006 7.6 5.1 5.8 1020 0.2 3.10 -

EGWA 2/14/2006 7.6 12.2 3.2 928 1.3 0.90 -

EGWA 3/8/2006 8.9 6.9 6.1 1072 0.2 1.20 -

EGWA 4/4/2006 7.7 3.9 15.1 952 0.2 1.10 1.23

EGWA 5/4/2006 8.6 2.9 19.2 592 0.2 2.60 0.11

EGWA 6/1/2006 8.1 2.5 24.8 1360 0.2 1.80 1.17

EGWA 7/20/2006 8.2 7.3 27.0 1472 0.2 1.80 0.78

Table A.6. Water quality data. Values that exceed threshold are in bold.

APPENDIX A

appendix a
96

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

96

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Station DATE pH DO

(mg L-1)

Temp

(oC)

ANC

(μeq L-1)

Sal NO3

-

(mg L-1)

TP

(μg L-1)

EGWA 8/3/2006 8.2 6.4 28.4 1616 0.2 2.50 1.22

EGWA 9/12/2006 7.9 9.1 19.3 1496 0.2 1.20 1.22

EGWA 10/11/2006 8.0 8.6 16.3 1176 0.1 2.50 0.94

EGWA 11/21/2006 7.9 10.8 8.6 880 0.1 1.90 0.36

EGWA 12/21/2006 8.6 9.9 5.9 1208 0.2 - 0.86

EGWA 3/19/2007 7.8 10.5 6.0 864 0.3 4.06 0.29

EGWA 4/18/2007 7.9 11.0 9.6 840 0.1 5.23 0.26

EGWA 5/22/2007 7.8 6.1 18.8 1432 0.2 1.79 0.21

EGWA 6/25/2007 8.3 7.5 22.6 992 0.2 0.70 0.20

EGWA 7/30/2007 7.9 6.0 25.2 1600 0.2 0.60 0.32

EGWA 9/4/2007 8.3 5.9 22.7 1960 0.3 0.90 0.49

FEBR 6/27/2005 7.6 6.9 21.2 1584 - 1.90 0.99

FEBR 10/4/2005 7.3 3.0 17.3 1144 - 0.50 0.38

FEBR 11/3/2005 7.7 8.5 12.1 1360 - 2.90 1.60

FEBR 12/8/2005 7.4 9.4 2.2 1380 1.5 1.60 0.23

FEBR 1/3/2006 7.1 5.4 7.4 940 0.2 2.00 1.90

FEBR 2/14/2006 7.6 12.8 3.0 1240 2.2 1.70 0.36

FEBR 3/8/2006 7.8 9.3 4.7 1384 0.4 2.40 0.48

FEBR 4/4/2006 7.3 3.3 11.6 1312 0.3 1.30 0.69

FEBR 5/4/2006 7.5 1.7 14.8 1856 0.4 3.50 0.51

FEBR 6/1/2006 7.3 1.3 20.1 2168 0.4 3.10 2.07

FEBR 7/20/2006 7.6 5.5 23.3 2256 0.4 4.20 1.25

FEBR 8/3/2006 7.6 3.6 25.0 2432 0.4 3.70 2.35

FEBR 9/11/2006 7.3 - 19.7 2040 0.4 2.00 1.26

FEBR 10/10/2006 7.5 4.6 15.1 1728 0.3 3.60 1.18

FEBR 11/21/2006 7.8 9.8 7.6 1800 0.4 4.60 0.21

FEBR 12/21/2006 7.7 7.7 7.8 1504 0.4 - 0.93

FEBR 1/30/2007 0.0 11.8 0.9 1440 - 1.37 0.57

FEBR 3/7/2007 7.6 10.0 2.3 1584 0.6 3.15 0.15

FEBR 4/19/2007 7.5 10.4 9.9 1704 0.4 2.42 0.13

FEBR 5/22/2007 7.3 4.8 15.1 3224 0.4 1.12 1.24

FEBR 6/25/2007 7.3 5.4 19.7 2112 0.4 1.40 0.38

FEBR 7/30/2007 7.4 4.6 22.7 1456 0.2 0.60 0.59

FEBR 9/4/2007 7.3 4.5 20.4 1440 0.4 1.20 0.31

FEBR 10/11/2007 6.9 3.1 18.2 1960 0.3 1.80 0.26

FEBR 11/5/2007 7.6 6.3 9.3 2168 0.5 2.50 0.30

FEBR 12/3/2007 7.1 7.6 7.6 1240 0.1 2.00 0.32

HACR 10/4/2005 7.7 8.0 17.9 1296 - 1.40 2.39

HACR 11/3/2005 7.9 8.9 10.4 1580 - 2.70 2.84

HACR 12/8/2005 7.8 12.2 2.4 1910 0.9 1.40 0.79

Table A.6. Water quality data. Values that exceed threshold are in bold (continued).
97

APPENDIX A

Station DATE pH DO

(mg L-1)

Temp

(oC)

ANC

(μeq L-1)

Sal NO3

-

(mg L-1)

TP

(μg L-1)

HACR 1/3/2006 7.7 4.8 7.5 1440 0.3 3.30 1.37

HACR 2/14/2006 7.5 11.3 4.9 1568 0.9 1.80 0.36

HACR 3/8/2006 8.5 8.3 5.8 1664 0.3 1.70 0.33

HACR 4/4/2006 7.9 4.0 13.1 1664 0.4 1.80 0.06

HACR 5/4/2006 7.6 2.1 16.1 1288 0.4 4.20 0.71

HACR 6/1/2006 7.7 2.3 21.4 2440 0.4 3.90 2.70

HACR 7/20/2006 7.8 7.1 23.3 2064 0.4 3.80 1.46

HACR 8/3/2006 7.9 5.8 24.9 2176 0.4 3.60 1.90

HACR 9/12/2006 7.5 8.8 17.4 2096 0.4 2.30 1.60

HACR 10/11/2006 7.8 8.0 15.9 1848 0.4 13.50 1.56

HACR 11/21/2006 8.0 10.7 7.5 2000 0.4 3.50 0.39

HACR 12/21/2006 8.2 8.7 7.5 2016 0.4 - 1.67

HACR 1/30/2007 - 12.9 2.5 1560 0.4 1.17 1.22

HACR 3/19/2007 8.1 11.3 5.6 1304 0.3 2.66 0.51

HACR 4/18/2007 7.9 10.2 10.6 1576 0.3 2.59 0.53

HACR 5/22/2007 7.8 7.3 16.2 1896 0.3 2.54 0.62

HACR 6/25/2007 7.9 6.7 20.3 1960 0.3 1.40 0.78

HACR 7/30/2007 7.9 6.6 22.5 2232 0.3 1.00 0.92

HACR 9/4/2007 7.7 5.8 20.5 1728 0.4 2.00 1.03

HACR 10/11/2007 - ------

HACR 11/5/2007 7.8 7.6 9.3 2232 0.5 4.40 0.69

HACR 12/3/2007 7.8 9.5 7.9 1896 0.3 2.00 0.69

LUBR 10/4/2005 7.5 7.2 20.0 1184 - 2.70 1.37

LUBR 11/3/2005 7.4 6.2 14.1 1160 - 3.90 3.22

LUBR 12/8/2005 7.6 7.6 7.7 1420 0.5 2.90 0.68

LUBR 1/3/2006 7.6 4.9 10.9 1300 0.3 5.80 1.09

LUBR 2/14/2006 7.5 13.8 2.4 1296 1.7 0.90 1.41

LUBR 3/8/2006 8.4 9.7 4.1 1520 0.2 1.00 0.53

LUBR 4/4/2006 7.7 4.2 13.6 1288 0.3 2.90 0.23

LUBR 5/4/2006 7.7 3.1 17.3 1456 0.3 5.80 1.47

LUBR 6/1/2006 7.5 3.0 20.7 1528 0.3 5.60 2.89

LUBR 7/20/2006 7.7 7.2 22.5 1656 0.4 6.50 1.28

LUBR 8/3/2006 7.7 6.7 23.9 1664 0.3 5.10 1.59

LUBR 9/12/2006 7.5 7.3 18.9 1800 0.4 3.60 4.96

LUBR 10/10/2006 7.6 6.6 17.8 1528 0.3 5.50 1.70

LUBR 11/21/2006 7.9 10.2 11.4 1540 0.4 - 0.46

LUBR 12/21/2006 7.9 7.5 10.1 1464 0.3 6.40 1.00

LUBR 1/30/2007 - 11.3 5.4 1344 0.4 1.72 0.80

LUBR 3/19/2007 7.8 8.2 7.5 1440 0.5 3.06 0.30

LUBR 4/19/2007 7.9 10.2 12.5 1624 0.4 3.77 0.36

Table A.6. Water quality data. Values that exceed threshold are in bold (continued).

appendix a
98

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

98

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Station DATE pH DO

(mg L-1)

Temp

(oC)

ANC

(μeq L-1)

Sal NO3

-

(mg L-1)

TP

(μg L-1)

LUBR 5/22/2007 7.5 6.9 16.0 1712 0.4 5.35 0.68

LUBR 6/25/2007 7.5 6.2 20.4 1872 0.4 3.10 0.26

LUBR 7/30/2007 7.5 5.8 22.9 1712 0.3 2.10 0.71

LUBR 9/4/2007 7.7 6.3 21.3 1904 0.3 3.00 1.19

LUBR 10/11/2007 7.3 4.4 18.1 - 0.3 2.10 1.26

LUBR 11/5/2007 7.7 7.6 12.2 2016 0.4 4.20 1.28

LUBR 12/3/2007 7.5 7.2 10.3 1624 0.2 2.80 0.86

NOST 10/3/2007 7.5 3.8 19.5 1680 0.3 5.80 0.79

NOST 11/1/2007 7.6 7.0 13.3 1304 0.3 4.60 0.58

NOST 11/26/2007 7.5 7.7 9.6 1216 0.3 5.80 0.26

PACR 11/8/2005 7.3 7.0 13.0 1080 - 3.60 0.99

PACR 1/26/2006 6.8 12.3 6.7 960 0.3 6.30 0.61

PACR 2/28/2006 7.8 10.0 5.5 920 0.3 3.90 -

PACR 4/12/2006 8.1 3.1 13.4 1024 0.3 2.90 1.50

PACR 5/18/2006 7.4 2.5 14.2 1168 0.3 4.30 8.82

PACR 1/12/2007 7.6 10.8 6.2 1048 0.3 5.50 1.11

PACR 2/23/2007 7.8 10.6 6.5 1088 0.5 3.93 0.74

PACR 3/27/2007 8.6 9.9 14.6 1024 0.3 4.10 0.41

PACR 5/14/2007 7.4 7.2 14.3 1288 0.3 4.05 0.17

PACR 10/3/2007 7.0 6.3 18.7 1472 0.3 5.70 0.46

PACR 11/1/2007 7.5 5.4 13.4 1448 0.3 4.60 0.42

PACR 11/26/2007 7.3 7.3 9.4 1568 0.3 4.60 0.33

PHBR 10/4/2005 7.4 7.8 17.3 1384 - 0.40 0.69

PHBR 11/3/2005 7.6 6.6 9.8 1420 - 1.70 1.79

PHBR 12/8/2005 7.5 9.0 1.7 1340 1.1 0.30 0.41

PHBR 1/3/2006 7.7 5.6 6.7 1280 0.2 2.50 0.44

PHBR 2/14/2006 7.7 11.9 9.0 1312 0.7 3.00 0.48

PHBR 3/8/2006 8.3 7.6 9.8 1272 0.3 3.10 0.15

PHBR 4/4/2006 8.0 6.0 11.4 1280 0.2 0.70 -

PHBR 5/4/2006 7.8 3.9 14.5 1664 0.2 2.80 0.61

PHBR 6/1/2006 7.5 2.6 20.2 2160 0.2 1.50 3.33

PHBR 7/20/2006 8.9 12.0 27.7 1792 0.3 4.10 0.68

PHBR 8/3/2006 7.5 3.7 24.9 1744 0.2 2.30 1.58

PHBR 9/12/2006 7.2 6.4 18.0 1768 0.2 1.00 1.03

PHBR 10/10/2006 7.4 7.9 15.1 1448 0.2 2.00 1.35

PHBR 11/21/2006 7.8 9.4 7.5 1780 0.2 2.70 0.25

PHBR 12/21/2006 8.0 8.8 5.3 1640 0.2 - 1.20

PHBR 1/30/2007 - 12.6 0.6 1560 0.5 1.07 1.10

PHBR 3/7/2007 8.1 11.3 1.6 1768 0.3 1.68 0.16

PHBR 4/19/2007 8.0 11.3 9.5 1784 0.2 1.52 0.11

Table A.6. Water quality data. Values that exceed threshold are in bold (continued).
99

APPENDIX A

Station DATE pH DO

(mg L-1)

Temp

(oC)

ANC

(μeq L-1)

Sal NO3

-

(mg L-1)

TP

(μg L-1)

PHBR 5/22/2007 7.3 5.5 14.4 1912 0.2 1.42 0.35

PHBR 6/25/2007 7.2 4.8 19.4 1656 0.2 0.60 0.31

PHBR 7/30/2007 7.1 4.1 22.3 1432 0.1 0.30 0.35

PHBR 9/4/2007 7.2 3.2 20.0 1272 0.2 0.40 0.46

PHBR 10/11/2007 - ------

PHBR 11/5/2007 - ------

PHBR 12/3/2007 7.4 7.1 6.9 1608 0.2 2.10 1.08

PYBR 10/4/2005 7.5 7.2 19.0 1232 - 1.80 0.64

PYBR 11/3/2005 7.9 9.2 10.4 1340 - 2.70 1.59

PYBR 12/8/2005 7.4 8.8 2.0 1400 0.4 2.40 0.20

PYBR 1/3/2006 7.6 4.5 7.3 970 0.2 3.90 0.64

PYBR 2/14/2006 7.5 11.6 4.5 1328 0.6 2.20 0.06

PYBR 3/8/2006 8.1 8.7 6.7 1464 0.3 2.30 -

PYBR 4/4/2006 7.6 3.8 15.0 1256 0.2 1.70 0.25

PYBR 5/4/2006 8.4 3.4 21.4 1488 0.3 5.30 0.49

PYBR 6/1/2006 8.2 3.0 25.6 1512 0.3 4.40 1.45

PYBR 7/20/2006 7.7 6.0 23.1 1776 0.2 2.30 1.23

PYBR 8/3/2006 8.4 8.7 29.4 1872 0.3 3.70 0.89

PYBR 9/12/2006 7.5 8.0 18.7 1776 0.3 3.30 1.57

PYBR 10/11/2006 8.0 7.0 16.6 1768 0.3 3.90 1.85

PYBR 11/21/2006 8.0 11.5 7.3 1600 0.3 5.40 0.16

PYBR 12/21/2006 8.5 11.5 6.5 1528 0.3 - 0.74

PYBR 1/30/2007 - 15.1 0.9 1312 0.3 1.70 0.57

PYBR 3/19/2007 8.1 12.9 6.2 1216 0.3 2.89 0.08

PYBR 4/18/2007 8.6 14.0 11.1 1208 0.3 2.30 0.19

PYBR 5/22/2007 7.7 8.0 19.4 1480 0.3 4.09 0.37

PYBR 6/25/2007 8.2 8.6 22.5 1768 0.3 1.50 0.32

PYBR 7/30/2007 8.3 7.5 24.6 1856 0.3 1.50 0.40

PYBR 9/4/2007 8.8 9.5 23.3 3048 0.3 2.00 0.32

PYBR 10/11/2007 7.6 6.7 17.5 2304 0.3 3.10 0.50

PYBR 11/5/2007 7.8 8.8 9.0 1928 0.3 4.00 0.33

PYBR 12/3/2007 7.4 6.4 7.2 1264 0.2 2.00 0.46

ROC3 10/3/2007 7.6 6.5 19.8 1864 0.2 2.10 0.36

ROC3 11/1/2007 7.7 8.3 11.7 1472 0.2 1.90 0.40

ROC3 11/26/2007 7.8 9.3 7.8 1872 0.2 2.30 0.30

ROCR 6/27/2005 7.5 5.6 23.2 1264 - 1.00 0.85

ROCR 10/4/2005 7.3 5.3 17.6 1320 - 1.80 0.84

ROCR 11/3/2005 7.3 6.7 9.9 900 - 1.70 1.01

ROCR 12/8/2005 7.2 9.4 1.5 960 0.8 0.70 -

ROCR 1/3/2006 7.2 3.1 5.8 940 0.2 3.90 -

Table A.6. Water quality data. Values that exceed threshold are in bold (continued).

appendix a
100

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

100

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Station DATE pH DO

(mg L-1)

Temp

(oC)

ANC

(μeq L-1)

Sal NO3

-

(mg L-1)

TP

(μg L-1)

ROCR 2/14/2006 6.8 10.3 2.7 952 1.1 0.80 -

ROCR 3/8/2006 7.2 7.6 4.6 968 0.2 1.50 0.16

ROCR 4/4/2006 6.9 2.5 13.9 864 0.2 0.90 -

ROCR 5/4/2006 7.3 1.8 16.2 792 0.2 2.50 0.08

ROCR 6/1/2006 7.4 0.9 22.8 1640 0.2 1.60 1.15

ROCR 7/20/2006 7.3 3.3 25.1 1456 0.2 2.10 0.62

ROCR 8/3/2006 7.5 2.9 27.0 1664 0.2 2.20 1.10

ROCR 9/11/2006 7.1 5.9 20.9 552 0.2 1.10 0.43

ROCR 10/10/2006 7.0 5.4 15.1 1032 0.1 1.80 0.88

ROCR 11/21/2006 7.6 9.4 8.6 760 0.1 0.80 0.29

ROCR 12/22/2006 7.5 8.0 6.1 1024 0.2 0.90 0.77

ROCR 1/30/2007 - 11.7 0.1 912 0.3 2.70 0.71

ROCR 3/7/2007 7.4 10.4 2.7 904 0.2 1.06 0.17

ROCR 4/19/2007 7.4 8.1 9.6 832 0.1 2.60 0.25

ROCR 5/22/2007 7.3 4.8 16.7 1288 0.2 1.69 0.43

ROCR 6/25/2007 7.0 6.1 21.4 1664 0.2 0.90 0.47

ROCR 7/30/2007 7.3 3.8 24.1 1248 0.1 0.80 0.53

ROCR 9/4/2007 7.3 4.8 21.5 2208 0.3 0.70 0.47

ROCR 10/11/2007 7.3 3.7 19.5 2400 0.3 1.30 0.48

ROCR 11/5/2007 7.6 6.8 9.0 1680 0.2 2.00 0.23

ROCR 12/3/2007 7.3 8.2 6.4 1304 0.1 2.30 0.48

SVPS 11/3/2005 7.4 7.6 11.2 1340 - 3.10 1.42

SVPS 12/8/2005 8.1 13.7 2.1 2150 0.8 1.70 0.55

SVPS 1/3/2006 7.8 5.0 8.1 1240 0.2 3.60 1.31

SVPS 2/14/2006 8.1 13.4 4.9 1744 1.1 1.70 0.62

SVPS 3/8/2006 8.9 10.7 5.5 2080 0.4 1.70 0.38

SVPS 4/4/2006 8.9 5.6 13.7 1584 0.3 2.00 0.31

SVPS 5/4/2006 8.2 2.6 16.7 2288 0.3 4.60 1.52

SVPS 6/1/2006 7.8 3.3 21.7 2552 0.4 3.40 2.66

SVPS 7/20/2006 8.0 7.2 23.5 2336 0.4 4.70 1.78

SVPS 8/3/2006 8.0 6.1 24.9 2544 0.4 4.10 1.62

SVPS 9/12/2006 7.6 8.4 18.0 2320 0.3 2.40 1.80

SVPS 10/11/2006 7.9 8.7 16.5 2376 0.3 4.20 1.84

SVPS 11/21/2006 8.2 11.1 7.5 1960 0.4 4.30 0.52

SVPS 12/21/2006 8.4 9.7 6.5 1544 0.4 - 1.35

SVPS 1/30/2007 - 13.6 0.9 2320 0.5 1.31 1.21

SVPS 3/19/2007 8.2 12.0 4.3 1952 0.4 1.96 0.11

SVPS 4/18/2007 8.5 13.9 9.6 1968 0.4 1.75 0.23

SVPS 5/22/2007 7.9 7.1 15.2 2408 0.1 2.34 0.99

SVPS 6/25/2007 7.9 7.4 20.3 1808 0.4 1.70 1.09

Table A.6. Water quality data. Values that exceed threshold are in bold (continued).
101

APPENDIX A

Station DATE pH DO

(mg L-1)

Temp

(oC)

ANC

(μeq L-1)

Sal NO3

-

(mg L-1)

TP

(μg L-1)

SVPS 7/30/2007 7.9 6.8 23.1 2168 0.3 1.10 0.63

SVPS 9/4/2007 8.1 6.7 20.7 2352 0.4 2.40 1.02

SVPS 10/11/2007 8.1 6.6 17.5 3128 0.4 3.00 0.99

SVPS 11/5/2007 8.1 9.1 9.7 2736 0.4 3.70 0.90

SVPS 12/3/2007 7.8 9.2 8.2 1560 0.2 1.90 0.88

Mean 7.8 7.5 13.5 1597 0.4 2.61 0.93

SE 0.01 0.2 0.5 31 0.0 0.10 0.06

Table A.6. Water quality data. Values that exceed threshold are in bold (continued).

Site ID BIBI

LRLR 425 1.50

LRLR 425 1.00

LRLR 426 1.00

LRLR 429 2.25

LRLR 434 1.00

NCRW 304-N-2004 2.11

Mean 1.48

SE 0.24

Table A.7. Benthic index of biotic integrity (BIBI). 

Values that exceed threshold are in bold.

Site ID PHI

NCRW-304-N-2004 61.3

LRLR 425 55.5

LRLR 425 56.5

LRLR 425 49.5

LRLR 425 44.5

LRLR 425 63.5

LRLR 426 65.0

LRLR 426 58.5

Mean 56.79

SE 2.47

Table A.8. Physical habitat index (PHI). Values 

that exceed threshold (> 42) are in bold.

appendix a
102

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

102

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Site ID Year Species

Invasive

basal area

Total shrub 

basal area

% invasive

by basal area

SHRUBS

ROCR-0094 2006 Euonymus alatus 45.36 78 58.15

ROCR-0010 2006 0 0.00

ROCR-0092 2006 0 0.00

ROCR-0172 2007 Viburnum plicatum 185.5 2217 8.37

ROCR-0186 2007 Viburnum sieboldii 405.18 406 99.80

TREES

ROCR-0094 2006 0 0.00

ROCR-0010 2006 0 0.00

ROCR-0092 2006 0 0.00

ROCR-0172 2007 0 0.00

ROCR-0186 2007 Acer platanoides 289.53

ROCR-0186 2007 Malus sieboldii 81.71 24917 0.33

Site ID Year Species

Mean

% cover

Error

(std. dev.)

Total

% cover

HERBACEOUS

ROCR-0092 2006 Alliaria petioloata 33 10

 Ampelopsis brevipedunculata 2 1

 Duchesnea indica 0.1 0.1 35.1

ROCR-0010 2006 0 0

ROCR-0094 2006 0 0

ROCR-0172 2007 Alliaria petiolata 0.1 0.1

Duchesnea indica 3 2

Hedera helix 16 3

Celastrus orbiculatus 6 2

Rosa multifl ora 0.1 0.1

Euonymus fortunei 0.1 0.1

Lonicera japonica 0.1 0.1 25.4

ROCR-0186 2007 Hedera helix 40 13

Alliaria petioloata 2 1 42

Mean 20.5

SE 8.77

Table A.9. Proportion (%) of cover of invasive exotic shrubs, trees, and herbaceous plants. Values that exceed threshold 

(> 5%) are in bold.
103

APPENDIX A

Site ID Year Pest species 

observed

ROCR-0092 2006 0.00

ROCR-0010 2006 0.00

ROCR-0094 2006 0.00

ROCR-0172 2007 0.00

ROCR-0186 2007 0.00

Mean 0.00

Table A.10.Presence of forest pest species. Values that 

exceed threshold (> 1%) are in bold.

Site ID Year

Tree

seedlings

Shrub

seedlings Total

ROCR-0010 2006 0 0

ROCR-0092 2006 0 0

ROCR-0094 2006 12500 12500

ROCR-0172 2007 2500 12500 15000

ROCR-0186 2007 0 2500 2500

Mean 6000

SE 3221.02

Table A.11. Native seedling regeneration (seedlings ha-1). Values that do not meet the 

threshold (31,875 ha-1) are in bold.

Stream ID Year FIBI

LRLR425 2000 1.9

LRLR425 2000 3

LRLR425 2003 2.3

LRLR426 2003 2.1

LRLR426 2000 2.8

NCRW 304-N 2004 2.78

Mean 2.48

SE 0.18

Table A.12. Fish index of biotic integrity (FIBI). Values 

that exceed threshold (> 3) are in bold.

2005 2006 2007

Species % area occ SE % area occ SE % area occ SE

Desmognathu fuscus 20.71 13.09 42.42 12.28 56.82 13.67

Eurycea bislineata 92.3 9.84 83.77 9.72 76.02 11.33

Pseudotriton ruber 30.43 14.7 36.2 14.52 41.49 15.87

Table A.13. Proportion (%) of area occupied (PAO) by amphibians. Values that are outside the threshold range 

(20-80%) are in bold.

appendix a
104

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

104

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Species 2003 2007 2008

HIGHLY SENSITIVE

Mniotilta varia 0 1 0

Setophaga ruticilla 0 0 5

Seiurus motacilla 0 1 1

Oporornis formosus 00 0

Wilsonia citrina 00 0

Buteo lineatus 0 1 0

Dendroica virens 0 1 0

Helmitheros vermivorus 0 1 0

Number of species 0 5 2

Mean 2.33

SE 1.45

Table A.14. Presence of forest interior dwelling species (FIDS) of birds. Values that do not 

meet the threshold (> 1 highly sensitive species; > 4 sensitive species) are in bold.

SENSITIVE

Picoides villosus 0 6 3

Dryocopus pileatus 0 4 0

Empidonax virescens 7 20 25

Vireo olivaceus 5 25 22

Catharus fucescens 3 7 2

Hylocichla mustelina 5 55 14

Parula americana 01 0

Seiurus aurocapillus 0 15 3

Piranga olivacea 1 9 4

Number of species 59 7

Mean 7.00

SE 1.15

Table A.15. Deer density (deer km-2). Values that exceed the 

threshold (forest: 8 km-2; grassland: 20 km-2) are in bold.

Year Deer density 95% CI

2007 31.83 24.86-40.75

2006 22.09 15.51-31.45

2005 20.00 14.66-27.99

2004 28.91 23.16-36.08

2003 37.57 24.39-57.86

2002 22.92 17.35-30.28

2001 24.24 14.89-39.47

2000 23.60 13.70-40.50

Mean 26.40

SE 2.09
105

systems. The inland aquatic habitats are 

based primarily on the classifi cation system 

of wetland types used by the Ramsar 

Convention (see http://www.ramsar.org/ris/

key_ris.htm#type). It is acknowledged that 

the classifi cation scheme used here is not 

satisfactory, hence a review of the scheme 

is underway.

Table B.1. IUCN Habitats Classifi cation Scheme (Version 3.0)—www.iucnredlist.org/static/

major_habitats.

The habitat types listed below are standard 

terms used to describe the major habitat/s in 

which taxa occur. If recorded, these habitats 

are listed on the Fact Sheet page for each 

taxon. The three levels of the hierarchy are 

self-explanatory, as they use familiar habitat 

terms that take into account biogeography, 

latitudinal zonation, and depth in marine 

1. FOREST

1.1 Boreal

1.2 Subarctic

1.3 Subantarctic

1.4 Temperate

1.5 Subtropical/Tropical Dry

1.6 Subtropical/Tropical Moist Lowland

1.7 Subtropical/Tropical Mangrove Vegetation Above High Tide Level

1.8 Subtropical/Tropical Swamp

1.9 Subtropical/Tropical Moist Montane

2. SAVANNA

2.1 Dry Savanna

2.2 Moist Savana

3. SHRUBLAND

3.1 Subarctic

3.2 Subantarctic

3.3 Boreal

3.4 Temperate

3.5 Subtropical/Tropical Dry

3.6 Subtropical/Tropical Moist

3.7 Subtropical/Tropical High Altitude

3.8 Mediterranean-type Shrubby Vegetation

4. GRASSLAND

4.1 Tundra

4.2 Subarctic

4.3 Subantarctic

4.4 Temperate

4.5 Subtropical/Tropical Dry Lowland

4.6 Subtropical/Tropical Seasonally Wet/Flooded Lowland

4.7 Subtropical/Tropical High Altitude

5. WETLAND (INLAND)

5.1 Permanent Rivers/Streams/Creeks [includes waterfalls]

5.2 Seasonal/Intermittent/Irregular Rivers/Streams/Creeks

5.3 Shrub Dominated Wetlands

5.4 Bogs, Marshes, Swamps, Fens, Peatlands

5.5 Permanent Freshwater Lakes [over 8 ha]

5.6 Seasonal/Intermittent Freshwater Lakes [over 8 ha]

5.7 Permanent Freshwater Marshes/Pools [under 8 ha]

5.8 Seasonal/Intermittent Freshwater Marshes/Pools [under 8 ha]

5.9 Freshwater Springs and Oases

5.10 Tundra Wetlands [includes pools and temporary waters from snowmelt]

5.11 Alpine Wetlands [includes temporary waters from snowmelt]

5.12 Geothermal Wetlands

Appendix B: Information Used in Rock Creek Park 

Natural Resource Condition Assessment

APPENDIX B
106

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

106

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

5.13 Permanent Inland Deltas

5.14 Permanent Saline, Brackish or Alkaline Lakes

5.15 Seasonal/Intermittent Saline, Brackish or Alkaline Lakes and Flats

5.16 Permanent Saline, Brackish or Alkaline Marshes/Pools

5.17 Seasonal/Intermittent Saline, Brackish or Alkaline Marshes/Pools

5.18 Karst and Other Subterranean Hydrological Systems [inland]

6. ROCKY AREAS [E.G. INLAND CLIFFS, MOUNTAIN PEAKS]

7. CAVES AND SUBTERRANEAN HABITATS (NON-AQUATIC)

 7.1 Caves

7.2 Other Subterranean Habitats

8. DESERT

8.1 Hot

8.2 Temperate

8.3 Cold

9. MARINE NERITIC (SUBMERGENT NEARSHORE CONTINENTAL SHELF OR OCEANIC ISLAND)

9.1 Pelagic

9.2 Subtidal Rock and Rocky Reefs

9.3 Subtidal Loose Rock/Pebble/Gravel

9.4 Subtidal Sandy

9.5 Subtidal Sandy-Mud

9.6 Subtidal Muddy

9.7 Macroalgal/Kelp

9.8 Coral Reef

9.8.1 Outer Reef Channel

9.8.2 Back Slope

9.8.3 Foreslope (Outer Reef Slope)

9.8.4 Lagoon

9.8.5 Inter-Reef Soft Substrate

9.8.6 Inter-Reef Rubble Substrate

9.9 Seagrass (Submerged)

9.10 Estuaries

10. MARINE OCEANIC

10.1 Epipelagic (0-200 m)

10.2 Mesopelagic (200-1,000 m)

10.3 Bathypelagic (1,000-4,000 m)

10.4 Abyssopelagic (4,000-6,000 m)

11. MARINE DEEP BENTHIC

11.1 Continental Slope/Bathyl Zone (200-4,000 m)

11.1.1 Hard Substrate

11.1.2 Soft Substrate

11.2 Abyssal Plain (4,000-6,000 m)

11.3 Abyssal Mountain/Hills (4,000-6,000 m)

11.4 Hadal/Deep Sea Trench (> 6,000 m)

11.5 Seamount

11.6 Deep Sea Vents (Rifts/Seeps)

12. MARINE INTERTIDAL

12.1 Rocky Shoreline

12.2 Sandy Shoreline and/or Beaches, Sand Bars, Spits, Etc.

12.3 Shingle and/or Pebble Shoreline and/or Beaches

12.4 Mud Flats and Salt Flats

12.5 Salt Marshes (Emergent Grasses)

12.6 Tidepools

12.7 Mangrove Submerged Roots

Table B.1. IUCN Habitats Classifi cation Scheme (Version 3.0)—www.iucnredlist.org/static/

major_habitats (continued)
107

APPENDIX B

13. MARINE COASTAL/SUPRATIDAL

13.1 Sea Cliffs and Rocky Offshore Islands

13.2 Coastal Caves/Karst

13.3 Coastal Sand Dunes

13.4 Coastal Brackish/Saline Lagoons/Marine Lakes

13.5 Coastal Freshwater Lakes

14. ARTIFICIAL - TERRESTRIAL

14.1 Arable Land

14.2 Pastureland

14.3 Plantations

14.4 Rural Gardens

14.5 Urban Areas

14.6 Subtropical/Tropical Heavily Degraded Former Forest

15. ARTIFICIAL - AQUATIC

15.1 Water Storage Areas (over 8 ha)

15.2 Ponds (below 8 ha)

15.3 Aquaculture Ponds

15.4 Salt Exploitation Sites

15.5 Excavations (open)

15.6 Wastewater Treatment Areas

15.7 Irrigated Land [includes irrigation channels]

15.8 Seasonally Flooded Agricultural Land

15.9 Canals and Drainage Channels, Ditches

15.10 Karst and Other Subterranean Hydrological Systems [human-made]

15.11 Marine Anthropogenic Structures

15.12 Mariculture Cages

15.13 Mari/Brackish-culture Ponds

16. INTRODUCED VEGETATION

17. OTHER

18. UNKNOWN

Table B.1. IUCN Habitats Classifi cation Scheme (Version 3.0)—www.iucnredlist.org/static/

major_habitats (continued)

Table B.2. Exotic herbaceous species found in Rock Creek Park.

TSN Species

18857 Akebia quinata

184481 Alliaria petiolata

28632 Ampelopsis brevipedunculata

18835 Berberis thunbergii

506068 Celastrus orbiculatus

501347 Centaurea biebersteinii

36335 Cirsium arvense

18712 Clematis ternifl ora

25163 Duchesnea indica

27950 Euonymus fortunei

502801 Glechoma hederacea

29393 Hedera helix

42943 Hemerocallis fulva

TSN Species

25898 Lespedeza cuneata

35283 Lonicera japonica

35281 Lonicera spp.

503829 Microstegium vimineum

20889 Polygonum cuspidatum

20914 Polygonum perfoliatum

504683 Pueraria montana

18603 Ranunculus fi caria

24833 Rosa multifl ora

25017 Rubus phoenicolasius

505677 Viburnum dilatatum

30238 Vinca minor

27023 Wisteria sinensis

APPENDIX B
108

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

108

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

FOREST MONITORING REPORTS

Schmit, J.P. and J.P. Campbell. 2007. 

National Capital Region Network 2006 

Forest Vegetation Monitoring Report. 

NPS. NPS/NCRN/NRTR-2007/046.

Schmit, J.P. and J.P. Campbell. 2008. 

National Capital Region Network 2007 

Forest Vegetation Monitoring Report. 

NPS, Fort Collins, CO. NPS/NCRN/

NRTR—2008/125.

WATER MONITORING REPORTS

Norris, M., J. P. Schmit and J. Pieper. 2007. 

National Capital Region Network 2005 

- 2006 Water Resources Monitoring 

Report. Natural Resource Program 

Center, Fort Collins, CO. NPS/NCRN/

NRTR - 2007/066.

AMPHIBIAN MONITORING REPORTS

Mattfeldt, S. D., E.H. Grant and L.L. Bailey. 

2008. Amphibian Monitoring in the 

National Capital Region: A focus on 

lentic and lotic habitats. NPS, NCRN. 

NPS/NRTR/NCRN—2008/088.

Bates, S. 2007. National Capital Region 

Network 2006 Deer Monitoring Report. 

National Park Service, Fort Collins, CO. 

NPS/NCRN/ NRTR—2007/033.

PROTOCOLS

Schmit, J.P., D. Chojnacky, and M. Milton. 

2006. National Capital Region Network 

Long-Term Forest Monitoring Protocol 

Ver. 1.0. 

Bailey, L.L., E.H. Grant, and D. Mattfeldt. 

2007. National Capital Region Network 

– Amphibian Monitoring Protocol.

Table B.3. Reports for I&M data used in the natural resource condition assessment.

Dawson, D.K. and M.G. Efford. 2006. 

National Capital Region Network – 

Protocol for Monitoring Forest-Nesting 

Birds in National Park Service Parks.

Bates, S. 2006. National Capital Region 

Network Inventory and Monitoring 

Protocol Version 1.1: Distance and 

Pellet-Group Surveys.

Hilderbrand, R.H., R. Raesly and D. 

Boward. 2007. National Capital Region 

Network Biological Stream Survey 

Protocols.

LANDSCAPE DYNAMICS

Townsend, P.A., R.H. Gardner, T.R. 

Lookingbill, and C.C. Kingdom. 2006. 

National Capital Region Network – 

Remote Sensing and Landscape Patter 

Protocol for Long-Term Monitoring of 

Parks.

SURFACE WATER DYNAMICS

Norris, M. and G. Fisher. 2006. National 

Capital Region Network Surface Water 

Dynamics Protocol. Water Chemistry 

(Note: no report number, still draft):

Norris, M., J. Pieper and A. Cattani. 2008. 

National Capital Region Network 

Inventory and Monitoring Program 

Water Chemistry Monitoring Protocols. 

Natural Resource Report. NPS/NCRN/

NRR—2008/XXX.
109

APPENDIX B

UNIVERSITY OF MARYLAND CENTER OF 

ENVIRONMENTAL SCIENCE

Integration and Application Network 

(IAN): Tim Carruthers, Bill Dennison, Jane 

Hawkey, Lisa Florkowski

Appalachian Lab: Todd Lookingbill

US GEOLOGICAL SURVEY

Water Resources for MD/DE/D.C.: Cherie 

Miller

Patuxent Wildlife Research Center: Larissa 

Bailey, Deanna Dawson, Evan Grant 

Table B.4. Participants at the data scoping workshop held at the Center for Urban Ecology on 

June 20th, 2006.

NATIONAL PARK SERVICE

Rock Creek Park: Ken Ferebee, Joe Kish, Bill 

Yeaman 

Center for Urban Ecology: Scott Bates, 

Doug Curtis, Dan Sealy, Jeff Runde, Diane 

Pavek, Bob Stroik 

Inventory & Monitoring: Pat Campbell, 

Shawn Carter, Marian Norris, Geoffrey 

Sanders, John Paul Schmit

Exotic Plant Management: Sue Salmons

Aalto, Jaworski, and Schremp. 1969. A 

water quality study of the Rock Creek 

watershed—This report provides data 

on the existing water quality in Rock 

Creek, analyzes changes in the water 

quality since 1966, when corrective 

actions were taken, and publishes all 

water quality data collected since 1966.

Adams, Hadidian, Leedy, Manski, 

and Riley. 1991. Daytime resting 

site selection in an urban raccoon 

population—This article is part of the 

long-term raccoon ecology research at 

Rock Creek Park. The daytime resting 

habits and habitats of adult raccoons 

were determined using mark-recapture 

and radio telemetry techniques.

Anderson and McFaden. 1978. The 

vegetative community structure of the 

Glover-Archbold, Battery Kemble, and 

additional reservations of Rock Creek 

Park—This report presents information 

on the vegetation community 

structure, specifi cally dominant 

overstory trees and cover types, of 

Rock Creek Park. The information was 

gathered with on-site fi eld checking as 

well as use of aerial photos.

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown.

Anderson, Doe, Jones, Kramer, and 

McFaden. 1977. Rock Creek Park and 

Rock Creek and Potomac Parkway: 

vegetation community structure and 

automated classifi cation of vegetation 

communities—This report is the result 

of an effort to establish an information 

base on the vegetative communities of 

Rock Creek Park. Aerial photos were 

analyzed for vegetation information, 

fi eld checks were made to confi rm the 

data.

Aquatic Ecology Class. 1991. Analysis of 

the 27th street stream—Members of an 

aquatic ecology class at GW examined 

the biota and the abiotic characteristics 

of a stream in Rock Creek Park from 

January to April 1991. Results are 

presented here.

Aquiar. 1991. Ecological competition: 

ant interactions at bonanza food 

sources (Hymenoptera: Formicidae)—

Interspecifi c competition among ant 

species in three habitats was studied in 

Glover-Archbold Park for a senior thesis 

at Georgetown University.

Baer, Hadidian, Jenkins, Johnston, Manski, 

and Savarie. 1989. Acceptance of 

simulated oral rabies vaccine baits 

APPENDIX B
110

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

110

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

by urban raccoons—A study on the 

effectiveness of vaccinating raccoons 

for rabies using oral baited vaccines 

was conducted in Rock Creek Park. 

Bait cubes were distributed in the par 

containing a detectable substance. 

Raccoons were trapped and evaluated 

for the presence of rabies.

Bailey. 1923. Mammals of the District 

of Columbia—This article describes 

all the mammals reported to occur 

in the District of Columbia in 1923. 

Descriptions of natural history and 

some occurrences are given for each 

animal.

Baker. 1956. Hydraulics report for Rock 

Creek Park, Washington, D.C.—This 

report gives fl ow data for Rock Creek 

at 7 proposed bridge sites.

Baker. 1957. Hydraulics report 

supplement: Rock Creek Park, 

Washington, D.C.—This report gives 

fl ood fl ow data for Rock Creek at 

7 proposed bridge sites in order to 

supplement a previous report.

Banta and Horowitz. 1992. Rapid 

bioassessment of macroinvertebrates 

in select lotic waters of the District 

of Columbia—As part of a follow-up 

study on macroinvertebrates in D.C. 

streams, this report presents water 

quality assessments of 5 streams: 

Carroll branch, East Creek, Klingle 

Creek, Pinehurst Branch, and Soapstone 

Creek. Data includes water quality 

measurements and 

Banta, Fithian, and Horowitz. 1992. 

Final Report: National Park Service, 

National Capital Region, Urban Stream 

Survey Phase II—This study continues 

an investigation into the physical and 

biological conditions in urban streams 

and their changes over time. Phase II 

applies the background information in 

developing a classifi cation system for 

streams. 

Banta, Fithian, Horowitz, and Shellum. 

1991. Final Report: National Park 

Service, National Capital Region, 

Urban Stream Survey Phase I—This 

study began an investigation into 

the physical and biological conditions 

in urban streams and their changes 

over time. Phase I entailed selection 

of 6 park streams and collection 

of water quality, quantity, and 

macroinvertebrate data. 

Banta. 1993. Biological water quality 

of the surface tributary streams of 

the District of Columbia—This study 

examined water quality and habitat 

quality of 29 streams in the D.C. area, 

including 4 tributaries of Rock Creek. 

Animal species were identifi ed, erosion 

was examined, and chemical analysis 

was performed to assess the presence 

of pollutants.

Bassler. 1943. Geology in the Capital 

Parks—This paper presents and 

describes a tour of the geology of 

some of the National Capital Parks, 

starting from Potomac Park, going by 

the zoo, and including the downtown 

monuments.

Batra and Rudolph. 1975. Fungi in 

Rock Creek Park—This is a list of the 

scientifi c and common names of fungi 

found in Rock Creek Park.

Bean and Smith. 1899. List of fi shes 

known to inhabit the waters of the 

District of Columbia and vicinity—This 

is an annotated list of the fi sh species 

recognized in D.C. waters. Locations 

common to each fi sh are given.
111

APPENDIX B

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

Belew and Scott. 1987. Exotic plant 

survey of Hedera helix, Pachysandra 

terminalis, Vinca minor, and Euonymus 

fortune—Four areas within the park 

were surveyed for four species of exotic 

plants in the winter of 1986. The plants 

were mapped, as well as signifi cant 

native plants, and methods for control 

are recommended.

Belew, Scott, and Sporko. 1986. Rock 

Creek Park 1986 gypsy moth integrated 

pest management—This is a description 

of gypsy moth management in the 

Rock Creek Park in 1986, including egg 

mass and defoliation survey results, 

treatment histories, and maps of 

treated areas.

Bergendahl, Richards, and Wlaschin. 

1978. Riprap study for the Rock Creek 

basin, Washington, D.C.—This study 

determined a mean stone size required 

to prevent erosion in the Rock Creek 

channel throughout its length in D.C.

Besse and Watt. 1984. Identifi cation and 

prioritization of the water resources 

problems and research needs in the 

District of Columbia—A survey was 

conducted to identify and prioritize the 

water resources problems and research 

needs in the District of Columbia. The 

survey was directed to individuals 

knowledgeable of the District’s water 

resources. 

Bigoni, Hadidian, Stanyon, and Wienberg. 

1993. A standardized G-banded 

karyotype for the raccoon (Procyon 

lotor) compared with the domestic 

cat—This study of the chromosomes 

and genetic evolution of the raccoon 

used blood samples taken from 16 

raccoons in Rock Creek Park.

Blackburn. 1989. Metropolitan 

Washington climate review—These 

climate reviews present data on the 

temperatures and precipitation for 

D.C. for each time period. A map of 

precipitation levels is included.

Blake and Robbins. 1931. Cladonia in the 

District of Columbia and vicinity—This 

report presents a list of lichen species 

of the genus Cladonia occurring in the 

D.C. region. Locations of specimens are 

given.

Blonder. 1988. Non-chemical treatments 

of the problem exotic plants 

Ampelopsis brevipedunculata and 

Celastrus orbiculatus—This report 

describes an experiment on the effi cacy 

of four non-chemical control methods 

for exotic vine plants in Rock Creek 

Park from June to September 1988.

Boettcher. 1979. Survey and collection of 

wasps and associated insects in Rock 

Creek Park Meadows, Washington, 

D.C., March 15 through June 22, 1978—

This is the report of a collection of 

wasp and associated species in eight 

meadows in Rock Creek Park in 1978. 

71 specimens were collected. Flowering 

plants used were recorded and a list of 

the bee and wasp species is included.

Bowden and Yeaman. 1996. 

Macroinvertebrate sampling, 1996—

These are fi eld notes from sampling 

of stream macroinvertebrates in the 

winter of 1996 on Portal Branch, 

Fenwick Branch, Normanstone Run, 

Foundry Branch, and Hazen Run.

Bowman. 1967. Asellus kendi, a new 

isopod crustacean from springs in the 

eastern United States—A new species 

of crustacean was discovered in a 

spring in Rock Creek Park by Roman 

Kenk. The species is described here.

APPENDIX B
112

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

112

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

Briggs and Chriswell. 1979. Gradual 

silencing of Spring in Washington: 

selective reduction in species of birds 

found in three woodland areas over 

the past thirty years—This document 

describes a study of the reduction of 

bird species in three woodland areas, 

specifi cally Cabin John Island, GloverArchbold Park, and Rock Creek Park, 

over the period of 1947-1977.

Briggs. 1959. The fi rst Glover-Archbold 

Park census—This article contains 

species lists and results from a breeding 

bird census conducted in GloverArchbold Park in 1959.

Briggs. 1960. Glover-Archbold Park—

These articles contain species lists and 

results from annual breeding bird 

censuses conducted in Glover-Archbold 

Park.

Burchick. 1986. Annual auto wildlife road 

kill statistics from 1980 to 1985—This 

data table summarizes the numbers of 

each animal species recorded as road 

kill for each year from 1980 to 1986.

Bushong. 1990. Historic resource study: 

Rock Creek Park, District of Columbia—

This study focuses primarily on a 

survey of historic and existing cultural 

resources of Rock Creek before and 

after its establishment as a park. 

Information on historic and present day 

land uses is provided, however.

Butcher. 1943. The Capitals little 

wilderness: Rock Creek Park—This 

is a descriptive article of some of 

the wildfl owers occurring in Rock 

Creek Park in spring and summer and 

conservation problems facing the park.

Carroll and Flanagan. 1976. Mica 

schist, SDC-1, from Rock Creek Park, 

Washington, D.C.

Carroll and Flanagan. 1979. Mica 

Schist, SDC-1, from Rock Creek Park, 

Washington, D.C.—This describes a 

sample of mica shist excavated from a 

sewer tunnel in Rock Creek Park.

Center for Urban Ecology. 1980. Raw 

water quality fi eld data—These 

are data charts from fi eld and lab 

analysis of water quality of Rock Creek 

between 1980 and 1982.

Center for Urban Ecology. 1983. Field 

statistics for Rock Creek and Battery 

Kemble Tribs for water year 1983—

These are summary statistics of water 

quality data collected in 1983 from 

Rock Creek and Battery Kemble 

tributaries.

Center For Urban Ecology. 1987. Rock 

Creek Park gypsy moth integrated 

pest management 1987 annual 

report—This is a description of gypsy 

moth management in the Rock Creek 

Park in 1987, including egg mass and 

defoliation survey results, treatment 

histories, and maps of treated areas.

Center for Urban Ecology. 1989. Rock 

Creek Park gypsy moth integrated 

pest management 1989 annual 

report—This is a description of gypsy 

moth management in the Rock Creek 

Park in 1989, including egg mass and 

defoliation survey results, treatment 

histories, and maps of treated areas.

Center for Urban Ecology. 1990. Dutch 

Elm Disease--1990: Rock Creek 

Park, Rock Creek Parkway, GloverArchbold Park—This printout contains 

information about 7 elm trees in the 

Rock Creek Parks--the extent of dieback 

and any treatments made.
113

APPENDIX B

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

CH2m Hill. 1977. Rock Creek stormwater 

and water quality management study—

This study was conducted to provide 

information for the master plan 

for management of the watershed. 

The environmental setting of the 

watershed is described, including 

land use, physiography, and wildlife; 

hydrology, fl ood, and water quality 

data are given.

CH2m Hill. 1979. Rock Creek ultimate 

land use—These maps are part of the 

Watershed Conservation Study and 

depict the 10, 25, 50 and 100-year fl ood 

profi les for the Rock Creek system in 

D.C.

CH2m Hill. 1979. Rock Creek watershed 

conservation study—The purpose of 

this study was to compile baseline 

information for planning evaluations 

and to develop a set of action-oriented 

recommendations in order to mitigate 

the effect of fl ooding, erosion, 

pollution, and sedimentation in Rock 

Creek. 

CH2m Hill. 1984. Rock Creek spring 

inventory—This study compiled an 

inventory of spring locations and 

characteristics in Rock Creek Park in 

1983. Seasonal fl ow measurements and 

water quality samples were taken at 

each spring. Geologic and water source 

descriptions are also provided.

Chang, O’Conner, Wade, and Watt. 1993. 

Ground water resource assessment 

study for the District of Columbia: 

Final Report—This report describes the 

groundwater resources in the District, 

and details data gained from a study of 

6 sample wells installed to determine 

and monitor groundwater quality and 

the effect of pollutant runoff on it in 

D.C. 

Clark. 1932. The occurrence of butterfl ies 

in the District of Columbia—This 

section of a book describes the 

butterfl y species occurring in the 

D.C. area and the general habitat or 

locations of each.

Coffelt and Weissert. 1977. Survey of 

American chestnut trees existing in 

Rock Creek Park north of Military 

Road—A fi eld study in the park on the 

location and sizes of American chestnut 

trees.

Cohn. 1989. Will palm trees replace pines 

on the Potomac?—This article describes 

the projected effects of global warming 

on the D.C. area by 2050. Park areas 

along the Potomac would be fl ooded 

by the rising sea levels. A diagram of 

the fl ooding is included.

Conlin. 1981. Rock Creek intensive 

survey—This report is the result of 

a study to describe the major trends 

in water quality in Rock Creek Park 

and compare the results to 1978-1979 

sampling data.

Copley. 1978. Pathology record on deer 

killed in Rock Creek Park, 3/19/78—

These forms present results of a 

necropsy on a white-tailed deer killed 

in Rock Creek Park in 1978.

Coues and Prentiss. 1883. Avifauna 

Columbiana: being a list of birds 

ascertained to inhabit the District of 

Columbia, with the times of arrival and 

departure of such as are non-residents, 

and brief notices of habits, etc.—This 

is a description of all the birds known 

to occur in D.C. in the 1800s, including 

some natural history information and 

common habitats.

APPENDIX B
114

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ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

Coues and Prentiss. 1883. Topography of 

the District: Rock Creek Region—This 

article describes the topography and 

physiology of the Rock Creek region in 

D.C. Included is a map of the region.

Crane. 1995. Action plan for an exotic 

species—This is an IPM plan for 

controlling the exotic plant porcelain 

berry (Ampelopsis brevipedunculata) 

which is invading the park.

Criswell. 1957. 1957 Winter bird 

population studies—This article 

summarizes results of annual winter 

bird counts in Rock Creek Park and 

Cabin John Park in Washington, D.C. 

Following are specifi c accounts for each 

area.

Criswell. 1968. 1968 Breeding bird 

population studies—This article 

summarizes results of annual breeding 

bird counts in Rock Creek Park, GloverArchbold Park, Cabin John Park, and 

Woodend Park in Washington, D.C. 

Following are specifi c accounts for each 

area.

Criswell. 1969. 1969 Winter bird 

population studies—This article 

summarizes results of annual winter 

bird counts in Rock Creek Park, GloverArchbold Park, Cabin John Park, and 

Woodend Park in Washington, D.C. 

Following are specifi c accounts for each 

area.

Criswell. 1972. Winter bird population 

studies, 1972—This article summarizes 

results of annual winter bird counts in 

Rock Creek Park, Glover-Archbold Park, 

Cabin John Park, and Woodend Park in 

Washington, D.C. Following are specifi c 

accounts for each area, but these are 

not included in this reprint.

Criswell. 1973. Breeding bird population 

studies, 1973—This article summarizes 

results of annual breeding bird counts 

in Rock Creek Park, Glover-Archbold 

Park, Cabin John Park, and Woodend 

Park in Washington, D.C. Following are 

specifi c accounts for each area.

Criswell. 1973. Winter bird population 

studies, 1973—This article summarizes 

results of annual winter bird counts in 

Rock Creek Park, Glover-Archbold Park, 

Cabin John Park, and Woodend Park in 

Washington, D.C. Following are specifi c 

accounts for each area, but these are 

not included in this reprint.

Criswell. 1978. Winter and breeding bird 

population studies: 1977 and 1978—

This paper presents results of winter 

and breeding bird censuses in Rock 

Creek Park and Glover-Archbold Park in 

1977 and 1978.

Czaplak. 1983. The fi rst breeding record 

of brown creeper in the District of 

Columbia—This page documents 

the fi rst report of a breeding brown 

creeper in Rock Creek Park in May 

1983. This is the fi rst record for the 

District of Columbia.

Czaplak. 1983. Unusual breeding birds in 

RCP—This page documents the unusual 

birds documented as breeding in Rock 

Creek Park in May 1983.Details of the 

reports are included.

Czaplak. 1989. Bird survey--fi eld habitat in 

Rock Creek Park - October 1988—This 

is a list of species of birds observed in 

the fi eld habitat of Rock Creek Park in 

October 1988. Survey areas and results 

are summarized in the cover letter.

Czaplak. 1990. Fledgling screech owl—

This is a photo of a fl edgling screech 

owl taken in Rock Creek Park behind 
115

APPENDIX B

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

the Kennedy Warren building on 

3/19/90. This is an early nesting date for 

this area.

Czaplak. 1992. Connecticut warbler—This 

is a photo of a Connecticut warbler 

taken in Battery Kemble Park on 

9/14/92. This is a rarely seen migrant in 

this area.

Czaplak. 1992. Dickcissel—This is a photo 

of a dickcissel taken in Battery Kemble 

Park on 9/18/92. This is a rare migrant 

in this area.

Czaplak. 1993. Rock Creek migration 

census, 1989-1992—This packet 

contains the data lists from fall 

migration surveys of birds in Rock 

Creek Park from 1989 to 1992. An 

important plant for the birds is the 

giant ragweed.

Dames and Moore. 1982. Characterization 

of the resource variables of two spring 

habitats in Rock Creek Park—A study 

was conducted on 2 spring habitats 

in Rock Creek Park to assess impacts 

on environmental quality. Parameters 

examined were water quality, habitat, 

vegetation, topography, soils, geology, 

ground water recharge, and park 

usage. 

Davis. 1949. Rock Creek Park—This article 

describes the natural features of Rock 

Creek Park and lists birds observed in 

each season of the year.

Department of The Army. 1992. Lyme 

disease risk assessment no 16-61-AL92-

92, Walter Reed Army Medical Center, 

Washington, D.C. 26-29 May 1992—A 

collection of ticks from small mammals 

in Rock Creek Park was analyzed for 

Lyme disease and Rocky Mountain 

Spotted Fever and found to be without 

the disease vectors.

Didden, Droege, Hadidian, Handly, 

Huff, Sauer, Swarth, Williams, Blake, 

and Robbins. 1996. A city-wide 

breeding bird survey for Washington, 

D.C.—A breeding bird survey of the 

entire Washington D. C. area was 

conducted in 1993. Species richness 

and composition was analyzed by land 

use and distribution. Species lists are 

presented by land use, including parks, 

and maps are included.

Dietemann. 1975. A provisional inventory 

of the fi shes of Rock Creek, Little Falls 

Branch, Cabin John Creek, and Rock 

Run, Montgomery County, Maryland—

In 1974 surveys of fi sh populations 

and water quality throughout the 

Rock Creek system were conducted to 

supplement data obtained in previous 

studies. Land use changes have 

changed the composition of fi sh over 

time.

Disalvo and Whitlock. 1985. Integrated 

pest management 1985 gypsy moth 

program: Rock Creek Park and Great 

Falls, Virginia—This is a description of 

gypsy moth management in the Rock 

Creek Park in 1985, including egg mass, 

burlap, and male moth survey results.

Doria. 1984. Gold in the Washington area. 

The Beltway Naturalist.

Drake, Fleming, and McCartan. 1992. 

The Rock Creek shear zone: a major 

tectonic boundary in the central 

Appalachian Piedmont.

Dranitzke and Fleming. 1989. Pine 

survey—The results of a 1989 survey 

of the distribution of Virginia pine 

and other pine trees in the park are 

penciled onto the map. One map has 

details about the areas of diseased 

trees as well as other trees of special 

interest.

APPENDIX B
116

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

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ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

Dynamic Corporation. 1993. Rock Creek 

fi sheries study, fi nal report—The 

objectives of this 3-year study were to 

characterize the present and historic 

fi sh populations of Rock Creek, to 

identify habitat characteristics, and to 

make management recommendations.

Eac Helicopters. 1997. Rock Creek Park 

and Glover: infrared deer census—A 

survey of deer populations in Rock 

Creek and Glover parks was conducted 

using infrared imaging from a 

helicopter in 1997. The results are 

presented here.

Edmondson. 1988. 1987 Macroinvertebrate census of the District of 

Columbia—During the summer of 

1987 the District of Columbia sampled 

macroinvertebrates from 10 separate 

water bodies in the city to gather 

baseline data and to assess the current 

ecological status of streams. Some 

sampling sites were on Rock Creek.

Fales. 1950. 1950 Winter bird population 

studies—This article summarizes results 

of annual winter bird counts in Rock 

Creek Park in Washington, D.C.

Fales. 1951. 1951 Winter bird population 

studies—This article summarizes results 

of annual winter bird counts in Rock 

Creek Park in Washington, D.C.

Fales. 1977. Butterfl y counts in Rock Creek 

Park, Washington, D.C.—This report 

presents the results of a survey of 

the butterfl ies of Rock Creek in 1977. 

Species lists are included.

Fales. 1978. 1978 butterfl y counts in Rock 

Creek Park, Washington, D.C.—This 

report presents the results of a survey 

of the butterfl ies of Rock Creek in 

1978. Species lists are included.

Fales. 1978. A preliminary list of 

butterfl ies that may occur in Rock 

Creek Park—This report presents a 

species list of butterfl ies and skippers 

possibly occurring in Rock Creek Park.

Fales. 1978. Report of all-day butterfl y 

count in Rock Creek Park—This table 

lists the species of butterfl ies observed 

on 1 day in 1978 and the number of 

butterfl ies recorded.

Fales. 1978. Skippers and butterfl ies 

known from Rock Creek Park and 

the District of Columbia—This report 

presents a species list of butterfl ies 

and skippers possibly occurring in Rock 

Creek Park, including the months they 

are known to occur in.

Fales. 1979. 1979 Spring butterfl y counts 

in Rock Creek Park, Washington, D.C.—

This table lists the species of butterfl ies 

observed on 3 days in 1979 and the 

location of each observation.

Fales. 1980. Spring butterfl y counts at 

Boundary Bridge in Rock Creek Park, 

Washington, D.C.—This table lists the 

species of butterfl ies observed on 3 

days in 1980 at Boundary Bridge.

Fales. 1987. The butterfl ies of Rock Creek 

Park, Washington, D.C.—This paper 

describes the species of butterfl ies 

known to occur at Rock Creek Park. 

Fifty-eight species are documented.

Fales. 1988. 1988 butterfl y counts in Rock 

Creek Park, Washington, D.C.—This 

paper describes a survey of butterfl ies 

in Rock Creek Park in 1988. Species list 

of results are given as well as photos of 

the survey areas.

Fales. 1989. Skippers and butterfl ies 

known from Rock Creek Park and the 

District of Columbia—This chart lists 
117

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

species of butterfl ies and skippers and 

notes whether they are known to occur 

in Rock Creek Park.

Fales. 1989. Some butterfl ies observed in 

Rock Creek Park, Washington, D.C., in 

1989—This is a table of observations of 

butterfl ies along two survey routes in 

RCP in 1989.

Favre, Sherald, and Schneeberger. 1993. 

Gypsy moth management in Rock 

Creek Park, Washington, D.C.—This 

article describes the history of gypsy 

moth management in Rock Creek 

Park, including monitoring efforts, and 

control efforts.

Favre. 1993. 1992 Dutch elm disease 

suppression report—This memo 

describes the treatment of two elm 

trees in Rock Creek with cacodylic acid 

and includes the data printout of the 

program.

Favre. 1993. Rock Creek Park survey for 

hemlocks and HWA—This is the report 

of a survey of Rock Creek Park for 

hemlock trees and signs of the hemlock 

woolly adelgid. Little sign of adelgids 

were found.

Feller. 1995. An aquatic subterranean 

macroinvertebrate survey of Rock 

Creek and associated National Parks, 

Washington, D.C.—This progress 

report summarizes the fi ndings of a 

literature search and fi eldwork in 1994 

documenting aquatic subterranean 

macroinvertebrates in Rock Creek Park, 

Glover-Archbold Park, and other park 

units in D.C. The study focused on 

groundwater springs.

Fellows. 1950. Notes on the geology of 

Rock Creek Park, District of Columbia—

This paper presents and describes a 

geologic map of the park from 1949.

Ferguson. 1967. Potamocypris bowmani, 

a new freshwater ostracod from 

Washington, D.C.—A new species of 

ostracod was discovered in a spring in 

Rock Creek Park by Thomas Bowman. 

The species is described here.

Fleming and Kanal. 1992. Newly 

documented species of vascular plants 

in the District of Columbia—This paper 

presents a species list of the results of a 

survey of the vascular plants of ROCR, 

Columbia Island, Anacostia Kenilworth, 

and Oxon Run from 1986 through 

1990. Voucher specimens from the 

study were placed in the US National 

Herbarium.

Fleming and Kanal. 1995. Annotated 

checklist of vascular plants of Rock 

Creek Park, National Park Service, 

Washington, D.C.—This paper presents 

a species list of the results of a survey 

of the vascular plants of ROCR from 

1986 through 1994. Voucher specimens 

from the study were placed in the US 

National Herbarium in the District of 

Columbia and Vicinity collection.

Fleming and Kemball. 1990. Ranunculus 

fi caria mapping—The results of a 

1990 survey of the distribution of the 

exotic plant Ranunculus fi caria (lesser 

celandine).

Fleming and Rosenberg. 1982. Grasses 

identifi ed in Rock Creek Park meadows, 

Washington, D.C., 1977-1981—This 

report contains a list of grasses 

identifi ed from 9 meadows in Rock 

Creek Park from 1977 to 1981. The 

name, location, blooming dates, and 

relative abundance are given for each 

species.

Fleming and Tasha. 1990. Dogwood 

mapping—The results of a 1990 survey 

of the distribution of dogwood trees 

APPENDIX B

APPENDIX B
118

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

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ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

in the park are penciled onto the map. 

One map has details about the areas of 

diseased trees as well as other plants of 

special interest.

Fleming. 1977. Park Road meadow--what 

to do about it—This memo describes 

the current state of the Park Road 

meadow, listing problems, and makes 

management recommendations.

Fleming. 1978. The geology of the 

crystalline rocks of West-Central 

Washington, D.C.—This study 

investigated and mapped the 

crystalline rocks which underlie the 

Piedmont portion of Washington, D.C. 

Rock Creek Park was included in the 

upper half of the study area. The rock 

types are described in the text. 

Fleming. 1979. Plant and animal 

diversifi cation in an urban park 

through the development of 

meadows—This report details the 

history of the 3-year old meadow 

restoration program at Rock Creek, 

listing vegetation changes and bird use 

and covering the success and future of 

the program.

Fleming. 1980. Meadow plantings, 1980—

These are lists of plants planted in the 

Rock Creek meadows in 1980.

Fleming. 1981. Soil samples of six 

meadows and adjacent woods and 

lawns in Rock Creek Park—Eighteen 

soil samples were taken from six 

managed meadows in Rock Creek Park 

in June 1981 and analyzed for coarse 

fragment, particle size, pH, soluble 

salts, organic matter, magnesium and 

other ions, and soil series.

Fleming. 1981. Soil samples of six meadows 

and adjacent woods and lawns in Rock 

Creek Park - raw data—Eighteen soil 

samples were taken from six managed 

meadows in Rock Creek Park in June 

1981 and analyzed for coarse fragment, 

particle size, pH, soluble salts, organic 

matter, magnesium and other ions, and 

soil series. 

Fleming. 1987. Small mammal survey data 

1980-1987—These are original data 

sheets from a small mammal survey 

conducted in two meadows (Military 

Field and Sherrill Drive) in Rock Creek 

Park from 1980-1987. Trapping data 

includes species, weight, sex, and 

number of traps with animals in them.

Fleming. 1988. Problem exotic plants in 

Rock Creek Park—This lists the exotic 

plants found in Rock Creek Park , their 

habitat, and their habitat in the park.

Fleming. 1988. Signifi cant native plants 

in Rock Creek Park—This is a list of 

“signifi cant” plants observed in Rock 

Creek, including their reason for being 

on the list. Also included are a list of 

sig. plants not yet seen by the author 

but expected, and a list of problem 

exotic plants.

Fleming. 1993. Fascine planting in Rock 

Creek Park—This report describes 

attempts to revegetate and restore 

disturbed areas of Rock Creek Park 

using fascines and live stakes. Plantings 

were begun in 1988 and monitored for 

5 years.

Folkerth. 1988. Bird observation records 

for Rock Creek Park—Bird observations 

from Natural history fi eld observations 

(1976-1988), observation records (1973-

1987), and Christmas bird count records 

(1973-1987) were searched and a list of 

species observed in ROCR was compiled 

in order to be used for a checklist of 

birds.
119

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

Ford. 1979. Release of spotted 

salamanders—This memo describes the 

release of 5 spotted salamanders along 

Pinehurst Branch from collection sites 

in Oxon Cove.

Ford. 1983. Breeding birds of Rock Creek 

Park, Washington, D.C.—This is a list 

of bird species nesting in the parks of 

Northwest Washington, D.C., as well 

as 13 questionable nesters (in need of 

confi rmation).

Ford. 1991. Flowering dogwood seed 

collection—This note describes the 

collection of several thousand seeds 

of fl owering dogwoods in Rock Creek 

Park in September 1991. The seeds 

were sent to CUE for processing for the 

National Seed Lab.

Forgey. 1991. One Hundred Years of 

Serenity (Rock Creek Park, Washington, 

D.C.)—This article summarizes the 

history of the establishment and 

management of Rock Creek Park, 

discusses current problems, and the 

values of the urban forests and the 

historical aspects of the park.

Foster. 1964. Slides of chestnut trees—

These slides depict American chestnut 

trees in Rock Creek Park—diseased, 

fallen, reproducing, and Chinese 

chestnuts as well.

Fowler. 1945. The amphibians and 

reptiles of the National Capital Parks 

and the District of Columbia region—

This report contains a checklist of 

amphibian and reptile species reported 

to occur in Rock Creek Park, C&O Canal, 

Kenilworth, or Mt. Vernon.

Frank. 1954. The Rock Creek watershed—

This article describes the history of 

deterioration of Rock Creek, including 

data on soils, rainfall, and erosion.

Gabor. 1979. Fish spawning data, Rock 

Creek—These documents provide 

information on spawning survey results 

from 1979 surveys of Rock Creek, as 

well as lists of anadromous fi sh species.

Gallagher. 1991. Raccoon rabies in 

Washington, D.C.: (1988-1991): The 

geography of an urban epizootic—

This study examined the geographic 

distribution of raccoons, rabies 

accounts, and land uses from 1988 to 

1990. Data from Rock Creek Park is 

included.

Givens, Johnson, Kasim, Medlin, 

Schartzman, and Wright. 1982. Lead 

and cadmium biogeochemistry: a case 

study using lichens as monitors of 

airborne pollution.

Guerrero and Hadidian. 1986. Biological 

data for raccoons trapped in Rock 

Creek Park—These sheets contain 

biological data (size, weight, age, 

etc.) collected from raccoons trapped 

in Rock Creek Park in 1983 and 1984 

under a cooperative study involving the 

UDC, NPS, CDC, National Zoo, and the 

D.C. Health Dept.

Guerrero. 1993. Inventory and status of 

wetlands in the District of Columbia.

H.. 1953. Oaks native to the Washington, 

D.C. region—This report lists and 

describes the species of oak trees 

found in D.C. Locations of each species 

common to the national parks are 

given.

Hadidian, Manski, and Riley . 1997. 

Population density and survival of 

raccoons (Procyon lotor) in an urban 

national park—This paper presents 

the results of a study on raccoon 

populations in Rock Creek Park over 

APPENDIX B

APPENDIX B
120

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

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ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

an 8-year period. Raccoon densities 

and survival were monitored using 

mark-recapture techniques and radio 

tracking. Average density for the park 

was 1 raccoon per 0.8 ha.

Hadidian, Manski, and Riley. 1998. 

Population density, survival, and rabies 

in raccoons in an urban national 

park—This paper presents the results 

of a study on raccoon populations 

in Rock Creek Park over an 8-year 

period. Raccoon densities and survival 

were monitored using mark-recapture 

techniques and radio tracking. 

Hadidian. 1983. Field notes from Hazen 

raccoon study—These are copies of the 

fi eld notebooks from the raccoon study 

by CUE at Hazen from 1983 to 1984.

Hadidian. 1987. Field notes from Nature 

Center raccoon study—These are 

copies of the fi eld notebooks from the 

raccoon study by CUE at the Rock Creek 

nature center from 1987 to 1991.

Hadidian. 1989. Field notes from Bingham 

raccoon study—These are copies of the 

fi eld notebooks from the raccoon study 

by CUE at Bingham from 1989 to 1990.

Hadidian. 1991. Citizen coon—In 1982 

a study of the behavior and ecology 

of urban raccoons Procyon lotor was 

started in the Rock Creek Park area 

of Washington D.C., but the study 

was soon expanded into a much more 

ambitious project when rabies reached 

Washington.

Haggerty, Onken, and Schneeberger. 

1989. Summary of 1989 gypsy 

moth suppression activities—This 

is a description of gypsy moth 

management in the Capital Region in 

1989, including maps of areas in the 

parks where Bacillus thuringiensis was 

sprayed. The Pinehurst area of Rock 

Creek was treated this year.

Harris. 1975. Distributional survey 

(Amphibia/Reptilia): Maryland and the 

District of Columbia—This survey lists 

the species of reptiles and amphibians 

occurring in MD and D.C. and provides 

a distributional map for each.

Hay. 1902. A list of the batrachians and 

reptiles of the District of Columbia and 

vicinity—This article describes species 

of reptiles and amphibians in D.C. and 

describes the location of the collection. 

Specifi c mention of Rock Creek is 

mentioned in reference to the black 

snake.

Hermann. 1941. A checklist of plants in 

the Washington-Baltimore area—This is 

a checklist of fl ora of the WashingtonBaltimore area, updating the 1918 fl ora 

by Hitchcock and Stanley. Locations of 

plants are not given.

Hermann. 1946. A checklist of plants in 

the Washington-Baltimore area—This is 

a checklist of fl ora of the WashingtonBaltimore area, updating the1918 fl ora 

by Hitchcock and Stanley. Locations of 

plants are not given.

Hitchcock and Standley. 1919. Flora of 

the District of Columbia and vicinity—

This is a systematic key to fl ora of the 

Washington area. Locations of some 

important specimens are given.

Holm. 1896. Fourth list of additions to the 

fl ora of Washington, D.C.—This paper 

presents additions to Ward’s Guide to 

the fl ora of Washington and Vicinity. 

Locations of specimens are given and 

some are from Rock Creek.

Horner and Sherman. 1935. Report on 

measures for elimination of pollution 
121

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

of Rock Creek and its tributaries 

in Washington—This report is a 

comprehensive investigation of the 

amount and source of pollution 

throughout the Rock Creek watershed. 

It includes information on fl ow rates, 

fl ood histories, precipitation data, 

water quality, and historical pollution 

reports.

Inashima. 1985. Archeological survey 

report: an archeological investigation 

of thirty-one erosion control and bank 

stabilization sites along Rock Creek 

and its tributaries—In association 

with planning for erosion control 

and bank stabilization measures 

along Rock Creek, the sites proposed 

for construction were surveyed for 

archeological value and cultural 

resources.

International Science & Technology, Inc. 

1989. Annual report: Rock Creek Park 

fi sheries study—This is the report of the 

fi rst year of a multi-year study of the 

fi sheries resources of Rock Creek Park. 

Progress on the following 6 tasks is 

described: search the information base; 

develop information on the fi sh species 

in the park; analyze instream migration 

barriers; evaluate the physical habitat 

of the creek; survey recreational 

fi shing; and develop management 

recommendation.

International Science & Technology, Inc. 

1992. Final report: Rock Creek Park 

fi sheries study: Year 2—This is the 

second annual report of a multi-year 

study of the fi sheries resources of Rock 

Creek Park. Progress on the following 

4 tasks is described: search the 

information base; develop information 

on the fi sh species in the park; evaluate 

the physical habitat of the creek; survey 

recreational fi shing; and develop 

management recommendation.

International Science & Technology, 

Inc. 1989. Information data base 

deliverable: Rock Creek Park fi sheries 

study—This is part of a multi-year 

study of the fi sheries resources of Rock 

Creek Park. This part is the result of 

identifying, assembling, and evaluating 

present and historical information 

sources relevant to the aquatic 

resources of Rock Creek. 

International Science & Technology, Inc. 

1991. Annual report: Rock Creek Park 

fi sheries study: Year 1 report—This is 

the fi rst annual report of a multi-year 

study of the fi sheries resources of Rock 

Creek Park. Progress on the following 

6 tasks is described: search the 

information base; develop information 

on the fi sh species in the park; analyze 

instream migration barriers; evaluate 

the physical habitat of the creek; survey 

recreational fi shing; and develop 

management recommendation.

International Science & Technology, 

Inc. 1991. Information data base 

deliverable: Rock Creek Park fi sheries 

study—This document is the result of 

a study to assemble information on 

the aquatic resources, including water 

quality, habitat, and fi sh species of Rock 

Creek in Maryland and D.C. One section 

summarizes ongoing research and one 

lists fi sh species known to occur.

James, Simmons, and Strain. 1994. 

Water resources data, Maryland and 

Delaware, water year 1994: Volume 1 

Surface-water data—This data contains 

one survey point within Rock Creek 

Park, called Rock Creek at Sherrill 

Drive. The 2 pages on this site contain 

discharge records by date and month 

as well as a chart of the fl ow over the 

year.

APPENDIX B

APPENDIX B
122

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ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

Johnson. 1989. 1988 rapid bioassessment 

of streams in the District of Columbia 

—During the summer of 1987 

the District of Columbia sampled 

macroinvertebrates from 10 separate 

water bodies in the city to gather 

baseline data and to assess the current 

ecological status of streams. This study 

was intended to fi ll in the gaps.

Johnsson. 1962. A checklist of vascular 

plants of the National Capital Region—

This checklist is the result of botanical 

collections made by the author in 

1961 and 1962. Date and location of 

collection are given, including sites 

in Rock Creek Park, Pinehurst Branch, 

C&O Canal, and Catoctin Mountain 

Park.

Johnston. 1962. The geology of 

Washington, D.C., and vicinity—This 

article describes the geology of D.C., 

including geological maps.

Johnston. 1964. Geology and groundwater resources of Washington, D.C., 

and vicinity—This study established an 

updated geological map of D.C. and 

used it to study groundwater resources 

in the region as well. 1022 wells and 

springs were sampled and analyzed 

chemically and physically.

Jorling. 1969. An analysis of the 

vegetation of Rock Creek National 

Park, Washington, D.C.—This master’s 

thesis study examined the plant 

communities of Rock Creek Park. 

Nineteen study plots were established 

for data collection on tree, shrub, 

and herbaceous layers. Soil samples 

were also examined for nutrient 

composition.

Kemball. 1990. Ranunculus fi caria: The 

northern fl oodplain: Rock Creek Park, 

and Glover-Archbold Park—These 

papers discuss the survey of these 

two parks for Ranunculus fi caria in 

the spring of 1990. Survey sites are 

described, and recommendations are 

made for managing this exotic plant.

Kerk. 1969. Observations on springs in the 

Washington, D.C. area—This lists by 

date a survey conducted on springs in 

the Rock Creek area looking for aquatic 

invertebrates.

Krakow. 1990. Historic resource study: 

Rock Creek and Potomac Parkway, 

George Washington Memorial 

Parkway, Suitland Parkway, BaltimoreWashington Parkway—This study 

focuses primarily on a survey of historic 

and existing cultural resources of 

these 4 areas before and after their 

establishment as a park. Information 

on historic and present day land uses is 

provided, however.

Lemov. 1985. Country walks. Travel 

Holiday.

Lewis. 1989. Rock Creek Park fi sh 

collection—These are fi sh specimens 

collected between 1989 and 1991 from 

Rock Creek.

Limno-Tech, Inc. 1994. Final Report: Urban 

Stream Study Phase III—This study 

continues an investigation into the 

physical and biological conditions in 

urban streams and their changes over 

time with the intent of developing a 

classifi cation system for identifying 

protection needs. 

Lipske. 1985. Night stalker (rabies study 

in Rock Creek Park, Washington, 

D.C.)—This brief article describes a 

study overseen by the Center for Urban 

Ecology of raccoons in Rock Creek Park. 

Raccoons were radio collared, tracked, 

and tested for rabies.
123

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

Loxley. 1991. Wildlife observations 1988-

1991—This is a compiled list of all 

wildlife sightings in Rock Creek from 

1988-1991.

Loxley. 1992. Ranunculus fi caria

mapping—The results of a 1992 survey 

of the distribution of the exotic plant 

Ranunculus fi caria (lesser celandine) in 

Pinehurst Branch are diagrammed on 

a map.

Ludwig. 1985. Element occurrences 

in Maryland near D.C.’s Rock Creek 

Park—This is a printout from the MD 

Natural Heritage database of element 

occurrences of special plants and 

animals in the vicinity of Rock Creek 

Park.

Manski. 1984. Field notes from Piney 

Branch raccoon study—These are 

copies of the fi eld notebooks from the 

raccoon study by CUE in Piney Branch 

from 1983 to 1984.

Maryland Department of Natural 

Resources. 1974. Maryland freshwater 

fi sheries data--Rock Creek—This is data 

from an electrofi shing survey of Rock 

Creek in September 1974. Each page 

is for a different segment of stream 

and describes the stream and sampling 

conditions and the fi sh found.

Maryland-National Capital Park 

and Planning Commission. 1979. 

Draft functional master plan for 

conservation and management in 

the Rock Creek Basin, Montgomery 

County, Maryland—This plan is the 

result of a study of the Rock Creek 

watershed in Maryland, giving 

policy recommendations based on 

stormwater and water quality data, 

fl oodplain analysis, and environmental 

inventories.

Maryland-National Capital Park And 

Planning Commission. 1985. A 

comprehensive amendment to the 

Upper Rock Creek Master Plan—This 

plan is the result of a study of the Rock 

Creek watershed in Maryland, giving 

policy recommendations based on 

stormwater and water quality data, 

fl oodplain analysis, and environmental 

inventories.

McAllister. 1985. An annotated checklist 

of the specimens from the Rock 

Creek Park jurisdiction deposited 

in the District of Columbia and 

vicinity collection of the US National 

Herbarium—This list is an annotated 

list of all the specimens of plants in 

the US National Herbarium which 

were collected from lands within the 

Rock Creek Park jurisdiction. The list is 

organized in multiple ways: by species, 

by location, and by collector.

McAtee. 1918. A sketch of the natural 

history of the District of Columbia 

together with an indexed edition of 

the US Geological Surveys 1917 map 

of Washington and vicinity—This is 

a comprehensive description of the 

natural history of the capital region, 

with specifi c sections on botany, 

insects, invertebrates, fi sh, reptiles and 

amphibians, birds, mammals, and biotic 

communities such as magnolia bogs. 

McAtee. 1930. Seventh supplement to 

the fl ora of the District of Columbia 

and Vicinity—This paper presents 

additions to Ward’s Guide to the fl ora 

of Washington and Vicinity. Locations 

of specimens are given and some are 

from Rock Creek.

McFarlane. 1975. Population 

investigations of the wood ducks (Aix 

sponsa) of Rock Creek Park—This 

senior thesis study was conducted 

APPENDIX B

APPENDIX B
124

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ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

to investigate wood duck habitats 

and populations in Rock Creek Park 

and identify methods to increase the 

populations within the park. Twenty-six 

ducks were found during the study.

Medford. 1950. A distributional survey of 

the fi shes of Rock Creek—This master’s 

thesis presents results of a survey of the 

Rock Creek fi sh populations from 1947 

to 1950. Fish were collected from the 

creek, water quality was measured, and 

habitat was analyzed.

National Capital Parks. 1944. A report 

treating of fl ood damage in the Rock 

Creek Valley, District of Columbia—This 

report describes an analysis of erosion 

and fl ood-caused damage to the Rock 

Creek valley conducted in the 1940s. 

The maps accompanying the report 

show the extent of high water in a 

1933 fl ood; changes in development 

extent; location of fl ood damage.

National Park Service, Denver Service 

Center. 1989. Map A: Park system of 

the nation’s capital and environs—Map 

shows National Park Service holdings in 

D.C. in green.

National Park Service, Denver Service 

Center. 1992. Draft environmental 

impact statement: Tennis stadium, Rock 

Creek Park, Washington, D.C.—Issues 

and concerns involved with activities 

at the Rock Creek Park Tennis Center 

are discussed within 7 alternatives for 

action. Impact to the effected natural 

environment is discussed, including 

vegetation, soils, wildlife, air quality, 

and water resources.

National Park Service, Water Resources 

Division. 1994. Baseline water quality 

data inventory and analysis: Rock 

Creek Park—This report was designed 

to inventory existing water quality 

data for the park and establish a 

water quality database for Rock Creek. 

Already existing data sources were 

inventoried and compiled, descriptive 

statistics were calculated on these data.

Newberry. 1974. Crystalline rocks in Rock 

Creek Park—These maps show the rock 

type distributions in Rock Creek Park, 

the “structural planes and axes,” and 

the “joint orientations.”

Nichols. 1960. Wintering bats in GloverArchbold Park—This article describes 

bats observed in Glover-Archbold park 

in the winter of 1960.

Norden. 1994. Rare species survey of 

four springs in Rock Creek Park, 

Washington, D.C.—This study looked 

at four springs in Rock Creek Park, 

sampling the fauna of the spring 

habitats and measuring water quality 

and quantity.

Northeast Team, Denver Service Center. 

1985. Adjacent land use study: Rock 

Creek Park, Washington, D.C.—This 

study was conducted in 1985 of land 

uses around Rock Creek park for the 

General Management Plan. One of the 

maps is of canopy vegetation in and 

around the park.

O’Brien and Gere. 1983. Appendix B: 

Macroinvertebrate survey of Rock 

Creek, Anacostia, and Potomac 

Rivers—This appendix to a sewer 

study details results of a survey of 

macroinvertebrates in Rock Creek and 

Anacostia and Potomac rivers. Species 

compositions are given by area.

O’Brien and Gere. 1986. Rock Creek 

Park outfall survey—This study was 

an investigation of all outfall sources 

falling into Rock Creek, Foundry 

Branch, and Battery Kemble Run during 
125

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

dry-weather. Outfalls which were 

found fl owing were further evaluated 

for chemical composition and water 

quality.

O’Connor. 1980. The city and its creek: 

implications for the 1980s from a half 

century of hydro-data.

O’Connor. 1982. Geological excursion 

through the Rock Creek Valley, NW 

Washington—This guidebook takes 

the reader on a trip around Rock Creek 

park area, describing the geology at 

each stop. Maps of D.C. geology are 

included.

O’Connor. 1986. Landforms and soil 

erosion in the Nation’s Capital. UDC 

Geoscience Guidebook: 5th annual 

Erosion and Sediment Control Program 

administrators conference.

O’Connor. 1986. Urban geology: satellite 

parkland for the NPS Rock Creek 

Division—This guidebook takes the 

reader on a trip around Rock Creek 

park area, describing the geology at 

each stop. Maps of D.C. geology are 

included.

O’Connor. 1989. Exploration of Rock Creek 

Park—North—This guidebook takes the 

reader on a trip around Rock Creek park 

area, describing the geology at each 

stop. Maps of D.C. geology are included.

O’Connor. 1989. Geological exploration 

of the southern Rock Creek Valley 

in D.C.—This guidebook takes the 

reader on a trip around the southern 

Rock Creek park area, describing the 

geology at each stop. Maps of D.C. 

geology are included.

Offi ce of Resource Management, Rock 

Creek Park. 1983. Rock Creek Park 

natural history fi eld observation 

reports and breeding bird census for 

1982—This document is a list of all 

wildlife sightings made in the park in 

1982. The list is separated by mammals, 

reptiles and amphibians, plants, birds, 

and other (fi sh, butterfl ies, mammal 

sign).

Olmstead Brothers. 1918. Rock Creek 

Park: a report—This report describes 

the value of Rock Creek Park, 

describing some of the natural features 

and landscapes, the areas of the park, 

and some of the future construction 

plans.

Onken. 1988. 1988 Gypsy moth 

suppression project report—This is a 

gypsy moth management report for 

Washington, D.C. in 1988, describing 

spray action location and monitoring.

O’Shaughnessy. 1969. Rock Creek Park--

trees and shrubs—This map is the result 

of a park ranger’s survey of the tree, 

shrub, and vine species of the park. 

Locations of each species are marked, 

and unusual occurrences are shown in 

red. Spring locations are also marked.

Partridge. 1991. Ecological competition: 

ant interactions—Interspecifi c 

competition among ant species in 

three habitats was studied in GloverArchbold Park for a senior thesis at 

Georgetown University.

Pease. 1982. Mammals of Rock Creek 

Park—These notes are the result of 

a search of the literature and the 

Rock Creek wildlife observation cards 

to compile a list of possible, and 

confi rmed mammals occurring in the 

park.

Pendleton. 1994. Factors controlling local 

temperature variation in an urban heat 

island—This master’s thesis examined 

APPENDIX B

APPENDIX B
126

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ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

the question of whether local air 

temperatures in an urban setting were 

related to tree density. Study sites 

included Rock Creek Park and GloverArchbold Park. Maximum temperatures 

were reduced by forest cover.

Petrides. 1943. Mammals of the National 

Capital Parks and the District of 

Columbia Region—This article describes 

all the mammals reported to occur in 

parks in the National Capital region. 

Descriptions of natural history and 

some occurrences are given for each 

animal in a table.

Pittman. 1990. Report of lichen species 

determined at Rock Creek Park—This 

memo identifi es specimens of lichens 

and bryophytes collected from Rock 

Creek in 1989.

Putz. 1995. Relay ascension of big trees 

by vines in Rock Creek Park, District 

of Columbia—This is a biological 

note describing observations of vines 

found on trees in Rock Creek Park, the 

different species, and their methods of 

climbing.

Quinn. 1987. Herp study-summer 1987—

This map shows the results of a herp 

survey done in the summer of 1987. 

Locations of herps observed are 

marked on the map.

Reed, Donnald, Widatalla, and Wilson. 

1953. The ferns and fern-allies of 

Maryland and Delaware including 

District of Columbia—This key to 

identifi cation of ferns also describes 

the history of plant studies in the D.C. 

area and the general distribution 

of ferns in the three areas. The key 

includes a description and range map 

of each species.

Reid. 1987. Attheyella (Mrazekiella) 

spinipes, a new harpacticoid copepod 

(Crustacea) from Rock Creek Regional 

Park, Maryland—A new species of 

crustacean was discovered in a spring 

in Rock Creek Park by William Yeaman 

and Stephen Syphax. The species is 

described here.

Reid. 1996. Checklist of the copepoda 

(Crustacea) of the District of 

Columbia—This list includes a list 

of copepod species identifi ed from 

collections of detritus from National 

Capital Parks and Rock Creek Park. Each 

species is listed by family and species 

and collection site, date, and collector.

Reiff. 1980. Water quality of streams 

in Montgomery County, Maryland: 

January-December 1989—This report 

presents water quality data on the 

streams of Montgomery County 

collected in the year 1989. Some 

sampling points are located on Rock 

Creek and are on the border of 

D.C. Data includes water chemistry, 

turbidity, pollution levels, and 

temperature.

Richards. 1934. A list of the mollusks of 

the District of Columbia and vicinity—

This article contains a list of mollusk 

species occurring in D.C. in 1934.

Richards. 1934. A list of the mollusks of 

the District of Columbia and vicinity—

This article contains a list of mollusk 

species known to occur in the waters of 

D.C. Specifi c locations are not given.

Robbins. 1979. Effect of forest 

fragmentation on bird populations—

This paper presents the results and 

trends of breeding bird censuses 

conducted in New Jersey, Maryland, 

and the District of Columbia, 

including Rock Creek Park and Glover-
127

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

Archbold Park. The data is examined 

to document the effect of forest 

fragmentation.

Roberts, Sherald, and Stidham. 1994. 

Evaluation of eight species of 

Cornus for resistance to dogwood 

anthracnose—A study on the survival 

of different species of dogwoods was 

conducted in Rock Creek Park. Trees 

were placed under a naturally infected 

canopy. The survival of the different 

species has been monitored. Only the 

Cornus fl orida was affected by the 

fungus.

Robertson. 1977. First annual Rock Creek 

Park herp hunt - April 23, 1977—This is 

a brief report listing the results of a 3 

hour search for amphibians and reptiles 

along Pinehurst Branch.

Rock Creek Park Staff. 1983. Gypsy 

moth pre-1988 data—These fi les 

contain various counts of gypsy moth 

infestations in D.C. Methods included 

male moth trapping, burlap wrap 

trapping, and egg mass counts.

Rock Creek Park Staff. 1988. Gypsy moth 

egg mass survey data—Data from 

annual surveys of the extent of gypsy 

moth egg masses in the Rock Creek 

Park.

Rock Creek Park Staff. 1988. Gypsy moth 

survey data fi gures—Data from annual 

surveys of the extent of gypsy moth 

egg masses and male moths have been 

plotted on various graphs.

Rock Creek Park Staff. 1989. Gypsy 

moth 1989, 1990 data—These fi les 

contain various counts of gypsy moth 

infestations in D.C. Methods included 

male moth trapping, burlap wrap 

trapping, and egg mass counts.

Rock Creek Park Staff. 1991. Gypsy moth 

egg mass survey data—Data from 

annual surveys of the extent of gypsy 

moth egg masses in the Rock Creek 

Park.

Rock Creek Park. 1975. Resource 

Management—The section in the 

annual report entitled Resource 

Management describes the activities of 

the resource management staff each 

year.

Rock Creek Park. 1991. Wildfi re 

management plan for Rock Creek Park, 

Washington, D.C.—This is the wildfi re 

management plan for the park. All 

wildfi res are to be suppressed and 

prevented.

Schlee. 1957. Fluvial gravel fabric. Journal 

of Sedimentary Petrology.

Schneeberger and Scott. 1988. Summary 

of 1988 gypsy moth suppression 

activities—This is a description of gypsy 

moth management in the Capital 

Region in 1988, including maps of 

areas in the parks where Bacillus 

thuringiensis was sprayed. Rock Creek 

Park was treated this year.

Schneeberger. 1987. Summary of 1987 

gypsy moth suppression activities and 

project review—This is a description 

of gypsy moth management in the 

Capital Region in 1987, including 

maps of areas in the parks where 

Bacillus thuringiensis was sprayed. 

The Pinehurst area of Rock Creek was 

treated this year.

Schneeberger. 1988. 1988 Gypsy moth 

suppression project report—This is a 

gypsy moth management report for 

Washington D.C. in 1988, describing 

spray action location and monitoring.

APPENDIX B

APPENDIX B
128

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ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

Seiger. 1993. The ecology and control 

of Reynoutria japonica (Polygonum 

cuspidatum)—This PhD dissertation 

study examined the status of Japanese 

knotweed in Rock Creek Park, 

predicted the potential for further 

invasion, and tested methods in a 

greenhouse for controlling the existing 

populations.

Shaw. 1977. Periods of fl owering of 

common fl owers, trees, and shrubs 

of Rock Creek Park—This is a list of 

common fl owers, trees, and shrubs of 

Rock Creek Park and the approximate 

dates that they fl ower.

Sherald. 1989. Dogwood anthracnose—

This memo describes a July 1989 survey 

for dogwood anthracnose in Rock 

Creek Park. Five areas were found with 

the disease, the fi rst occurrence in the 

District.

Shetler and Wiser. 1985. An annotated 

checklist of the specimens from the 

Rock Creek Park jurisdiction deposited 

in the District of Columbia and 

vicinity collection of the US National 

Herbarium—This list is an annotated 

list of all the specimens of plants in 

the US National Herbarium which 

were collected from lands within the 

Rock Creek Park jurisdiction. The list is 

organized in multiple ways: by species, 

by location, and by collector.

Shetler and Wiser. 1987. First fl owering 

dates for spring-blooming plants of 

the Washington, D.C. area for the 

years 1970 to 1983—A chart of the 

fi rst fl owering dates is presented 

for blooming plants in the D.C. area 

from observations in the Northwest 

D.C. area. Heavy observations were 

recorded in the C&O Canal and Rock 

Creek areas.

Shosteck. 1975. Fungi in Rock Creek 

Park—This is a list of the scientifi c and 

common names of fungi found in Rock 

Creek Park.

Shosteck. 1976. Field guide to Rock 

Creek Park—This report details 

information about all aspects of Rock 

Creek: geology, mammals, birds, fi sh, 

amphibians, insects, trees, fl owers, 

ferns, fungi, lichens, and maps of the 

park.

Shosteck. 1976. Periods of fl owering of 

common fl owers, trees, and shrubs of 

Rock Creek Park, Washington, D.C.—

This is a guide for visitors of common 

fl owers, trees, and shrubs of Rock 

Creek Park and the approximate dates 

that they fl ower.

Shosteck. 1977. Rock Creek watershed 

habitat survey and inventory of fauna 

and fl ora, Montgomery County, 

Maryland—This report describes the 

ecology and natural history of the Rock 

Creek watershed in Maryland. Included 

are inventories of fl ora and fauna 

complete with species lists.

Sidwell Friends School, Environmental 

Science Class. 1996. Rock Creek stream 

study: a water quality assessment—

Students at Sidwell Friends School, 

under direction of the teacher Paula 

Wang, have monitored water quality 

in Rock Creek since January 1995. This 

report summarizes the fi rst year’s data 

and presents data charts and tables of 

monthly samples of chemical analysis 

and macroinvertebrate sampling.

Sidwell Friends School, Environmental 

Science Class. 1997. Rock Creek stream 

study: a water quality assessment—

Students at Sidwell Friends School, 

under direction of the teacher Paula 

Wang, have monitored water quality 
129

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

in Rock Creek since January 1995. 

This packet contains the data from 

January 1996 through January 1997and 

presents data charts.

Smith. 1976. Soil survey of District of 

Columbia—This is the report of the soil 

survey for D.C., describing the soil types 

which are then mapped on the map 

sheets at the back. Maps corresponding 

to park areas can be selected using the 

index to map sheets. 

Spangler. 1976. Additions to 1975 Rock 

Creek fi sh survey—This list details fi sh 

species caught in Rock Creek Park in 

1976 on a rod.

Stanton. 1972. Bacteriological and 

chemical study of the Rock Creek 

watershed—This study was conducted 

by the University of Maryland and 

Montgomery College to conduct an 

intense bacteriological investigation of 

the Rock Creek watershed. Chemical 

and bacteria analysis was examined 

throughout the watershed.

Stidham. 1993. Dogwood anthracnose 

research in Rock Creek Park: Interim 

report 1—This is a progress report for a 

long-term monitoring study of dogwood 

anthracnose in Rock Creek Park. Trees 

were placed under a naturally infected 

canopy. Half of the trees were treated 

with a fungicide, and the survival of the 

groups has been monitored.

Stose. 1919. Travertine from Rock Creek 

Park, District of Columbia—This 

biological note describes the location 

of a travertine deposit at the mouth 

of a spring in Rock Creek Park. It 

may have originated from a reservoir 

feeding the spring.

Sullivan. 1957. Rock Creek Park 

observation—This preliminary report 

on the Rock Creek Ecological study lists 

plant and animal observations made 

as a part of an ecological survey of the 

park.

Syphax. 1986. Evaluation of manual 

grubbing, heat, and herbicide 

treatments as methods of managing 

ampelopsis.

Terborgh. 1992. Why American songbirds 

are vanishing—This article discusses 

the trend of decreasing songbirds in 

America. Breeding bird census data 

from Rock Creek Park is cited and 

included in a chart by species and year.

Thatcher. 1948. Breeding-bird population 

studies—This article reports the results 

of a breeding bird survey conducted 

in Rock Creek Park in 1947. The area is 

compared to Cabin John Island.

Thatcher. 1948. The Wood Thrush—This 

article reports the results of a winter 

bird survey conducted in Rock Creek 

Park in 1948. The area is compared to 

Cabin John Island.

The American University. 1977. Forest 

association maps—These overlays go 

with the park base map (aerial photos) 

and are a product of the American 

University vegetation cover type study. 

Twelve different forest associations 

were mapped, including a disturbance 

category.

The American University. 1977. Rock 

Creek Park photo base map—These 

are the park base map (aerial photos) 

and are accompanied by various Mylar 

overlays which depict water and forest 

resources.

The Rock Creek Study Project. 1972. 

Bacteriological and chemical study of 

the Rock Creek watershed—This study 

APPENDIX B

APPENDIX B
130

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Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

was conducted by the University of 

Maryland and Montgomery College 

to conduct an intense bacteriological 

investigation of the Rock Creek 

watershed. Chemical and bacteria 

analysis was examined throughout the 

watershed.

Thomas. 1969. Survey of areas for 

signifi cant natural values—This survey 

was designed to develop methods for 

identifying signifi cant natural features 

and presents preliminary results of 

its application in describing singular 

natural features of National Capital 

Parks. Features of all the capital parks 

are listed.

Thomas. 1972. Determination of new 

species of trees in Rock Creek Park—

This note describes the occurrence of 

three tree species unusual to the park.

Thomas. 1997. Changes in dominance 

on the Rock Creek Park fl ood plain, 

District of Columbia—This document is 

a scientifi c note describing observations 

on the Rock Creek fl oodplain 

vegetation and suggesting a change in 

the dominance structure of the trees 

over time.

Thompson. 1976. Flood-plain delineation 

for Rock Creek basin, Washington, 

D.C.—This study determined 10, 25, 

50, and 100-year fl ood profi les for the 

Rock Creek system in D.C. Hydraulic 

data from the USGS was used and is 

included in an appendix.

Thompson. 1995. Audubon Naturalist 

Society water quality monitoring 

program—These are data sheets from 

a water quality monitoring program 

by the Audubon Naturalist Society 

on Pinehurst Branch since 1995 and 

on Rock Creek since 1997. Habitat 

and water quality are assessed, and 

macroinvertebrates are sampled in 3 

sampling periods. 

Tufty et al. 1994. Rock Creek watershed: 

a compendium of articles—Articles 

from park resource personnel, local 

scientists, and activists address topics 

such as plants, fi sh, butterfl ies, birds, 

geology, pollution control, and 

preservation issues.

US Army Corps of Engineers. 1989. 

Anadromous fi sh passage study, Rock 

Creek, District of Columbia—This 

report examines passage problems 

for migratory fi sh in Rock Creek and 

proposes solutions for getting the fi sh 

over the barriers. Fish migrating in 

the creek include alewife, blueback 

herring, and white perch. 

USGS. 1983. Topographic maps of Rock 

Creek—These are various topographical 

quadrangle maps of the area of Rock 

Creek Park.

Van Huizen. 1978. Fishing survey of 

Rock Creek Park—This study was to 

determine human fi shing pressures and 

types of fi shing in the park. Fishermen 

were interviewed in the spring of 1978 

and were asked about their reasons for 

fi shing, type and size of fi sh caught, 

and equipment used.

Van Huizen. 1978. Second annual Rock 

Creek Park herp hunt - April 29, 1978—

This is a brief report listing the results 

of a 3 hour search for amphibians and 

reptiles along Pinehurst Branch.

Venables. 1990. Preliminary assessment 

of the susceptibilities of non-target 

Lepidopteron species to Bacillus 

thuringiensis (Bt) and dimilin used for 

gypsy moth suppression—This study 

was designed to estimate the impact 

of gypsy moth suppression programs 
131

Table B.5. Listing of known literature pertaining to Rock Creek Park, Washington D.C., based 

on a query of NPS NatureBib made on November 26, 2008. Brief abstract information is 

provided. Citations not having a date or author are not shown. (continued)

on non-target Lepidopterons using 

species observed in Catoctin Mountain 

Park, National Capital Parks-East, Prince 

William Forest Park, and Rock Creek 

Park. 

Water Resources Management Division, 

District of Columbia. 1992. The 

District of Columbia water quality 

assessment—This report provides 

a water quality assessment of the 

District’s water resources, based on 

water quality monitoring data which is 

also summarized here. The appendices 

have data broken down by water body, 

including streams administered by Rock 

Creek Park.

Wheelock. 1993. Cultural landscape 

report: Pierce-Klingle Mansion, 

Rock Creek Park—The purpose of 

this report was to trace the physical 

history of the site of the Pierce-Klingle 

mansion, document and compile 

signifi cant landscape characteristics, 

and recommend preservation of the 

landscapes.

Wilsnack. 1991. Ecological competition: 

ant interactions (Hymenoptera: 

Formicidae)—Interspecifi c competition 

among ant species in three habitats 

was studied in Glover-Archbold Park 

for a senior thesis at Georgetown 

University.

Yeaman. 1986. Sewer line crossings 

notes—These notes describe 

observations of sewer line crossings 

on Rock Creek and its tributaries and 

mention threats of pollution, leaks, or 

erosion.

Zug. 1975. Possible extirpated species—

This is a list compiled from Smithsonian 

records of possible extirpated species 

of reptiles and amphibians and the last 

known record of their presence, some 

of which were in Rock Creek Park.

APPENDIX B

APPENDIX B
132

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

132

ROCK CREEK PARK NATURAL RESOURCE CONDITION ASSESSMENT

Acronym Description

AL Appalachian Laboratory (UMCES)

ANC Acid Neutralizing Capacity

ANTI Antietam National Battlefi eld (NPS-NCRN)

AWQC Ambient Water Quality Criterion

BIBI Benthic Index of Biotic Integrity

BSS Biological Stream Survey

CASTnet Clean Air Status and Trends Network

CATO Catoctin Mountain Park (NPS-NCRN)

CHOH Chesapeake & Ohio Canal National Historical Park (NPS-NCRN)

CUE Center for Urban Ecology (NPS-NCRN)

D.C. District of Columbia

DC DOE District of Columbia Department of the Environment

DCMR District of Columbia Municipal Regulations 

DO Dissolved Oxygen

FIBI Fish Index of Biotic Integrity

FIDS Forest Interior Dwelling Species of birds

FRS Freshwater Recreational Standards

GWMP

HAFE

George Washington Memorial Parkway

Harpers Ferry National Historical Park (NPS-NCRN)

I&M Inventory & Monitoring Program (NPS)

IAN Integration & Application Network (UMCES)

IBI Index of Biotic Integrity

ISA Impervious Surface Area

IUCN International Union for Conservation of Nature

MANA Manassas National Battlefi eld Park (NPS-NCRN)

MBSS Maryland Biological Stream Survey

MD DNR Maryland Department of Natural Resources

MDN Mercury Deposition Network

MONO Monocacy National Battlefi eld (NPS-NCRN)

NAAQS National Ambient Air Quality Standards

NACE National Capital Parks-East (NPS-NCRN)

NADP National Atmospheric Deposition Program

NPS National Park Service

NPS ARD NPS Air Resources Division

NCRN National Capital Region Network

NSDWS National Secondary Drinking Water Standards

PAO Proportion (%) of Area Occupied

PHI Physical Habitat Index

Table B.6. List of acronyms.
133

Table B.6. List of acronyms. (continued)

Acronym

PRWI

Description

Prince William Forest Park (NPS-NCRN)

RESAC Regional Earth Science Applications Center

ROCR Rock Creek Park (NPS-NCRN)

RTE Rare, Threatened, and Endangered

SMCL Secondary Maximum Contaminant Level

TP Total Phosphorus

UMCES University of Maryland Center for Environmental Science

U.S. EPA U.S. Environmental Protection Agency

USDA U.S. Department of Agriculture

USGS U.S. Geological Survey

WOTR Wolf Trap National Park for the Performing Arts (NPS-NCRN)

APPENDIX B

APPENDIX B
134
135

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