U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2009–5020

In cooperation with the Pennsylvania Department of Transportation Engineering District 6-0

Physical and Vegetative Characteristics of a Newly 

Constructed Wetland and Modified Stream Reach, 

Tredyffrin Township, Chester County, Pennsylvania,

2000–2006
1

2

3

Cover.

1. View of the upstream rock deflector, June 2001. 

2. Riparian-buffer plantings in group 15, September 2005. 

3. View of the constructed wetland from photo station 3, September 2006.

4. View of downstream rock deflector, September 2006. 

4
Physical and Vegetative Characteristics 

of a Newly Constructed Wetland and 

Modified Stream Reach, Tredyffrin 

Township, Chester County, Pennsylvania,

2000–2006

By Jeffrey J. Chaplin, Kirk E. White, and Leif E. Olson

In cooperation with the Pennsylvania Department of Transportation Engineering District 6-0

Scientific Investigations Report 2009–5020

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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Suggested citation:

Chaplin, J.J., White, K.E., and Olson, L.E., 2009, Physical and vegetative characteristics of a newly constructed wetland and modified stream reach, Tredyffrin Township, Chester County, Pennsylvania, 2000–2006: U.S. Geological 

Survey Scientific Investigations Report 2009-5020, 64 p.
iii

Contents

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

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

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

Description of the Study Area ............................................................................................................4

Wetland-Compensation Site......................................................................................................4

Modified Stream Reach..............................................................................................................4

Monitoring Methods......................................................................................................................................6

Wetland-Compensation Site ...............................................................................................................8

Stream Reach Surveys ........................................................................................................................9

Riparian Buffer....................................................................................................................................10

Physical and Vegetative Results ...............................................................................................................10

Constructed Wetland .........................................................................................................................10

Stream Channel...................................................................................................................................15

Hydrologic Conditions...............................................................................................................15

Changes to the Channel............................................................................................................15

Riparian Buffer....................................................................................................................................23

Summary........................................................................................................................................................29

References Cited..........................................................................................................................................30

Appendix 1. Photographs of the Constructed Wetland, Tredyffrin Township, Chester

County, Pennsylvania.....................................................................................................................33

Appendix 2. Water Levels in Plots Outside of the Constructed Wetland........................................41

Appendix 3. Plant Species Growing in Plots Outside of the Constructed Wetland..........................45

Appendix 4. Photographs of Surveyed Cross Sections and Rock Deflectors in Valley

Creek, Tredyffren Township, Chester County, Pennsylvania...................................................47

Appendix 5. Photographs of Selected Tree and Shrub Plantings in the Riparian Buffer,

Tredyffrin Township, Chester County, Pennsylvania ................................................................53
iv

Figures

1. Map showing location of the wetland-compensation site and modified stream

reach, Tredyffrin Township, Chester County, Pennsylvania ...........................................3

2. Map showing wetland-compensation site, Tredyffrin Township, Chester County,

Pennsylvania ...........................................................................................................................5

3. Photographs showing views of a berm for U.S. Highway 202 and a terrace that

bound the constructed wetland to the south, west, and north.......................................6

4. Map showing locations of the stabilization structures and riparian plantings

within the modified stream reach, Tredyffrin Township, Chester County,

Pennsylvania............................................................................................................................7

5. Graphs showing water levels at sampling plots within the constructed wetland,

Tredyffrin Township, Chester County, Pennsylvania, 2000-2006 ...................................13

6–14. Graphs showing: 

6. Longitudinal profile of the upstream reach of the modified stream reach,

Tredyffrin Township, Chester County, Pennsylvania...............................................17

7. Longitudinal profile of the downstream reach of the modified stream reach,

Tredyffrin Township, Chester County, Pennsylvania...............................................18

8. Surveys of the upstream cross section of the modified stream reach,

Tredyffrin Township, Chester County, Pennsylvania...............................................20

9. Surveys of the downstream cross section of the modified stream reach,

Tredyffrin Township, Chester County, Pennsylvania...............................................21

10. Comparison of particle-size distributions in the upstream cross section,

2001–2006 .......................................................................................................................22

11. Comparison of particle-size distributions in the downstream cross section,

2001–2006 .......................................................................................................................24

12. Number of planted trees and shrubs growing in the riparian buffer,

Tredyffrin Township, Chester County, Pennsylvania, 2001–2006...........................25

13. Percentage of planted species of trees and shrubs in the riparian buffer

that were stressed, Tredyffrin Township, Chester County, Pa., 2001–2006 .........26

14. Number of Acer negundo (box elder) and Gymnocladus dioicus (Kentucky

coffee tree) plants growing in the riparian buffer, Tredyffrin Township, 

Chester County, Pennsylvania, 2001–2006................................................................27
v

Tables

1. Summary of dates for data collection at the constructed wetland and modified

stream reach, Tredyffrin Township, Chester County, Pennsylvania .................................8

2. Areal cover of vegetation in the constructed wetland, Tredyffrin Township, Chester

County, Pennsylvania, 2000–2006 .........................................................................................11

3. Observations of hydric-soil indicators in the constructed wetland, Tredyffrin

Township, Chester County, Pennsylvania, 2000–2006 .......................................................14

4. Cumulative precipitation measured at Valley Forge National Historical Park for

water years 2000–2006, Montgomery County, Pennsylvania...........................................14

5. Longitudinal profile characteristics of the upstream reach of the modified stream

channel, Tredyffrin Township, Chester County, Pennsylvania.........................................16

6. Longitudinal profile characteristics of the downstream reach of the modified

stream channel, Tredyffrin Township, Chester County, Pennsylvania ...........................16

7. Cross-section dimensions and bed-particle-size distribution in the upstream reach

Tredyffrin Township, Chester County, Pennsylvania .........................................................19

8. Cross-section dimensions and bed-particle-size distribution in the downstream

reach Tredyffrin Township, Chester County, Pennsylvania..............................................23

9. Woody trees and shrubs growing in the riparian buffer, fall 2006 ..................................28

Conversion Factors and Abbreviations

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2

)

acre 0.004047 square kilometer (km2

)

square foot (ft2

) 0.09290 square meter (m2)

square mile (mi2

) 2.590 square kilometer (km2)

Flow rate

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

Abstract

To compensate for authorized disturbance of naturally 

occurring wetlands and streams during roadway improvements to U.S. Highway 202 in Chester and Montgomery 

Counties, Pa., the Pennsylvania Department of Transportation (PennDOT) constructed 0.42 acre of emergent wetland 

and 0.94 acre of scrub-shrub/forested wetland and modified 

sections of a 1,600-foot reach of Valley Creek with woody 

riparian plantings and streambank-stabilization structures 

(including rock deflectors). In accordance with project permits 

and additional guidance issued by the U.S. Army Corps of 

Engineers, the U.S. Geological Survey (USGS), in cooperation with PennDOT, collected data from 2000 through 2006 

to quantify changes in 1) the vegetation, soils, and extent of 

emergent and scrub-shrub/forested parts of the constructed 

wetland, 2) the profile, dimension, and substrate in the vicinity 

of rock deflectors placed at two locations within the modified 

stream reach, and 3) the woody vegetation within the planted 

riparian buffer. The data for this investigation were collected 

using an approach adapted from previous investigations so 

that technology and findings may be more easily transferred 

among projects with similar objectives.

Areal cover by planted and non-planted vegetation growing within the emergent and scrub-shrub/forested parts of the 

constructed wetland exceeded 85 percent at the end of each 

growing season, a criterion in special condition 25c in the 

U.S. Army Corps of Engineers project permit. Areal cover of 

vegetation in emergent and scrub-shrub/forested parts of the 

constructed wetland exceeded 100 percent in all but one growing season. Frequent and long-lasting soil saturation favored 

obligate-wetland species like Typha latifolia (broadleaf cattail) 

and Scirpus validus (great bulrush), both of which maintained 

dominance in the emergent wetland throughout the study 

(percent cover was 20 and 78 percent, respectively, in 2006). 

Echinocloa crusgalli (barnyard grass), an annual invasive 

from Eurasia, initially established in the newly disturbed soils 

of the scrub-shrub/forested wetland (areal cover was 56 percent in 2000), but by 2002, E. crusgalli was not growing in 

any sample plots and other species including Agrostis stolonifera (creeping bent grass), Festuca rubra (red fescue), Cornus 

spp. (dogwood species), and Salix nigra (black willow) were 

becoming more common. Sal. nigra contributed 30-percent cover in the scrub-shrub/forested wetland part by fall 

2003. Rapid colonization of this species in subsequent years 

increased annual cover through 2006, when 15- to 25-foot tall 

Sal. nigra trees dominated the tree/shrub stratum (48 percent 

of the areal cover in 2006). The understory of the scrub-shrub/

forested wetland was mostly shaded because of the canopy 

of Sal. nigra trees. Herbaceous species growing under and 

near the margins of the canopy included Ag. stolonifera and 

Ty. latifolia (29- and 23-percent areal cover, respectively).

Flows in Valley Creek are responsible for transporting 

sediment and shaping the channel. Annual mean streamflow 

during the period the modified stream reach was monitored 

ranged from 15.2 cubic feet per second (ft3

/s) in the 2002 

water year to 53.0 ft3

/s in the 2004 water year. This is a range 

of about 55 percent lower to 58 percent higher than the annual 

mean streamflow for the period of record. Despite the variability in streamflow, longitudinal profiles surveyed near rock 

deflectors in two short (100-foot) reaches within the modified stream reach maintained a constant slope throughout the 

monitoring period, most likely because of the presence of 

bedrock control. Cross-section geometry in the upstream reach 

was virtually unchanged during the monitoring period but 10 

feet of bank migration was measured downstream, leaving the 

rock deflectors installed to protect the bank in mid-stream. 

As indicated by the change in channel morphology at the 

downstream reach, it is apparent that the rock deflectors were 

ineffective at adequately protecting the bank from erosion. 

Particle distributions in both reaches, in general, became more 

fine over most of the monitoring period, with the exception 

of the 2006 assessment, which showed coarsening in the 15thand 50th-percentile size categories at the upstream reach. There 

was no evidence of deposition associated with the coarsening 

of the upstream reach in 2006, indicating transport capability 

was maintained or increased. The trend toward a finer particle 

Physical and Vegetative Characteristics of a Newly 

Constructed Wetland and Modified Stream Reach, 

Tredyffrin Township, Chester County, Pennsylvania,

2000–2006

By Jeffrey J. Chaplin, Kirk E. White, and Leif E. Olson
2 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

distribution in the downstream reach suggests a decrease in 

sediment transport commonly associated with channel widening.

Because of replacement plantings in 2001 and 2002, the 

most reliable time frame for interpretation of trends in the 

number and well being of riparian plantings is 2003–2006. 

The most prevalent tree species in 2003 was Platanus occidentalis (sycamore; 63 individuals), followed by Carpinus caroliniana (ironwood; 35), Quercus palustris (pin oak; 33), Alnus 

serrulata (smooth alder; 30), Acer rubrum (red maple; 26), 

Acer saccharinum (silver maple; 17), and Sal. nigra (10). The 

most prevalent shrubs in 2003 were Cornus spp. (98 individuals), followed by Salix discolor (pussy willow; 51), Physocarpus opulifolius (ninebark) and Viburnum dentatum (arrowood) 

(each with 28 individuals), Clethra alnifolia (summersweet; 

27), and Spirea virginiana (Virginia spirea; 4). Trees and 

shrubs that appreciably declined in number between 2003 and 

2006, including Sal. nigra, Al. serrulata, Ac. saccharinum, 

Sa. discolor, and Cl. alnifolia, generally exhibited more stress 

in 2003 compared to their counterparts that remained nearly 

constant or increased in number throughout the study. Despite 

replacement of dead individuals in 2001 and 2002, planted 

trees decreased from 214 in 2001 to 171 in 2006 and shrubs 

decreased from 546 in 2001 to 225 in 2006. By contrast, the 

combined number of the two most prevalent non-planted 

species [Acer negundo (box elder) and Gymnocladus dioicus

(Kentucky coffee tree)] more than doubled over the same time 

period (from 110 to 244 individuals). The density of planted 

species at the end the study was 382 plants per acre compared 

to 329 plants per acre for non-planted species.

Introduction

Maintenance and improvement of transportation infrastructure commonly necessitate alteration of existing stream 

channels and (or) naturally occurring wetlands. Compensatory 

mitigation for wetland and stream encroachments usually is 

required by Federal and State regulatory agencies and commonly includes modification or construction of wetlands, 

stream channels, and associated riparian buffers. From 1998 

through 2003, the Pennsylvania Department of Transportation (PennDOT) made roadway improvements to 5.5 mi of 

U.S. Highway 202 in Chester and Montgomery Counties, 

Pa. (fig. 1). Pursuant to Section 404 of the Clean Water Act, 

PennDOT was granted Federal and State permits to permanently impact naturally occurring wetlands and to enclose 

selected stream reaches including an unnamed tributary that 

drains to Valley Creek. To compensate for these authorized 

activities, a Federal Section 404 permit required PennDOT to 

construct at least 0.29 acre of emergent wetland and 0.94 acre 

of scrub-shrub/forested wetland and to modify a reach of Valley Creek that flows through Valley Forge National Historical 

Park (Valley Forge Park).

Wetland construction began in March 2000 and culminated with final grading and planting in May 2000. In addition, approximately 0.70 acre of natural wetland adjacent 

to the constructed wetland was enhanced with plantings of 

native shrubs and trees. The constructed wetland and enhanced 

natural wetland collectively are referred to as the wetlandcompensation site. Stream modifications included shrubs and 

trees planted from October through December 2000 throughout a riparian buffer adjacent to Valley Creek and stabilization 

structures installed within the active channel in the spring of 

2001.

In accordance with project permits and additional guidance issued by the U.S. Army Corps of Engineers (ACOE) 

to PennDOT and Tredyffrin Township, monitoring of the 

constructed wetland and stream modifications was conducted 

over seven consecutive growing seasons. The U.S. Geological Survey (USGS), in cooperation with PennDOT, collected 

data from 2000 through 2006 to quantify changes in 1) the 

vegetation, soils, and extent of the constructed wetland, 2) the 

profile, dimension, and substrate in the vicinity of stabilization 

structures placed in Valley Creek, and 3) the woody vegetation within the planted riparian buffer. These data provide 

PennDOT and ACOE with the information needed for them to 

assess the success of each project component.

Monitoring conditions and guidance specified in project 

permits require collection of quantitative and qualitative data. 

The data-collection methods used for this study were adapted 

from an approach recently (2000–2004) utilized by USGS 

(Chaplin and others, 2006) to monitor a relocated stream 

reach, constructed wetland, and riparian buffer in Lehigh 

County, Pa., approximately 50 mi north of the study area. 

Use of a consistent approach for data collection and storage 

enhances the ability to transfer results among other similar 

projects. Additional activities and associated methods that may 

be considered for future investigations include, but are not 

limited to, protocols for documentation of benthic-invertebrate 

communities, habitat, and (or) water quality as dictated by 

project objectives.

Purpose and Scope

This report presents a summary of data collected within 

a constructed wetland and a modified stream reach of Valley Creek during seven post-construction monitoring events 

between October 2000 and September 2006. This report provides PennDOT and ACOE with the information needed for 

them to determine the success of the constructed wetland, the 

stabilization structures placed in Valley Creek, and the riparian 

plantings adjacent to the creek. In general, the measure of success for the project components is ambiguously defined and is 

open to interpretation by government agencies with a regulatory mandate. Therefore, it is beyond the scope of this report 

to define success or to determine if the objectives of wetland 

construction or stream modification were successfully met.
Introduction 3

Figure 1. Location of the wetland-compensation site and modified stream reach, Tredyffrin Township, 

Chester County, Pennsylvania. 

40°

04'

00"

40°

05'

30"

78°28'00" 75°26'30"

0 0.5 1 MILE

VALLEY FORGE NATIONAL 

HISTORICAL PARK

PRECIPITATION STATION

STUDY AREA

PHILADELPHIA 

INTERNATIONAL 

AIRPORT

CHESTER

COUNTY

PHILADELPHIA

MONTGOMERY 

COUNTY

PENNSYLVANIA

Base map from U.S. Geological Survey digital data, 

Albers conic equal-area projection, 

North American Datum of 1983

TREDYFFRIN TOWNSHIP

UPPER MERION TOWNSHIP

VALLEY FORGE NATIONAL 

HISTORICAL PARK 
4 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Areal cover of vegetation, hydric-soils indicators, water 

levels, and the areal extent of the constructed wetland are 

presented. Changes to the profile, dimension, and substrate 

at selected locations along the modified stream reach were 

quantified by longitudinal and cross-section surveys and 

pebble counts. The density, condition, and richness of woody 

vegetation growing in planted areas of the riparian buffer 

also are presented. Photographs of the wetland and modified 

stream reach provide a graphic record of changes throughout 

the study period.

Description of the Study Area

The study area is in Chester County, Pa., and consists 

of the wetland-compensation site adjacent to U.S. Highway 

202 and sections of a 1,600-ft reach of Valley Creek that was 

modified with riparian plantings and rock placed to deflect 

flow (rock deflectors) and minimize erosion (fig. 1). All components of the study area are within the Lowland Section of 

the Piedmont Physiographic Province, which is characterized 

by broad valleys separated by broad low hills (Pennsylvania 

Department of Conservation and Natural Resources, 2000). 

The underlying bedrock is dominated by limestone and dolomite with some shale and sandstone (Sevon, 2000). Although 

karst features are common throughout much of the Piedmont, 

none were observed in or near the wetland-compensation site 

or modified stream reach.

Wetland-Compensation Site

The two components of the wetland-compensation site 

are the constructed wetland and the adjacent natural wetland 

that was enhanced with tree and shrub plantings in 2000 

(fig. 2). The focus of the monitoring was on the constructed 

wetland that encompasses at total of 1.36 acres characterized 

by 0.42 acre dominated by emergent herbaceous vegetation 

(termed the emergent (EM) part) and 0.94 acre dominated by 

planted and non-planted trees and shrubs (termed the scrubshrub/forested (SS/FO) part). The constructed wetland is 

bounded to the south by a berm for U.S. Highway 202 and on 

the west and north by a steeply sloping terrace (fig. 3). The 

boundary between the constructed wetland and the enhanced 

natural wetland is defined by the limit of excavation during construction. To the east, the boundary is a human-made 

rip-rap and earth berm that parallels Wilson Road (fig. 2). The 

berm is approximately 2–3 ft higher than the wetland surface 

and has three outlets of lower elevation (about 1.5 ft higher 

than the wetland surface).

The primary source of water for the wetland is stormwater that enters through a rip-rapped stormflow channel near 

the southwest corner and through a culvert near the southeast 

corner, along with base flow and stormflow from an intermittent unnamed tributary conveyed under U.S. Highway 202 by 

a box culvert (fig. 2). Water is detained by the berm along the 

east side, periodically submerging the wetland-compensation 

site. The unnamed tributary flowing through the site ultimately 

connects with Valley Creek approximately 1,700 ft upstream 

from the upstream terminus of the modified stream reach 

(fig. 1).

Native soils within the wetland-compensation site are 

predominantly Lindside Silt Loam (soil map unit Ln), a moderately well-drained soil with slopes of 0 to 3 percent (Natural 

Resources Conservation Service, 2008). Lindside Silt Loam is 

a common soil type on floodplains in the area, and it extends 

approximately 165 ft on either side of the unnamed tributary. 

Native soils in the western quarter of the site are Conestoga 

Silt Loam [soil map unit CtC, Natural Resources Conservation 

Service, 2008; formerly described as Hagerstown Silt Loam 

in previous soil surveys by Kunkle (1963)]. Native Conestoga Silt Loam soils are steeper (8 to 15 percent slopes) than 

Lindside Silt Loam soils, but flattening of the slopes during 

wetland construction resulted in 0 to 3 percent slopes when 

construction was complete. Soil profiles within and outside 

of the boundary of the constructed wetland were disturbed 

when the native soils were excavated. Amendments, including mulched leaves and topsoil, were added to the surface and 

mixed with native soils before planting (URS Greiner Woodward Clyde, 1999a).

Upon completion of wetland construction and soil preparation from March to May 2000, the EM part of the wetland 

was planted with a mixture of nine emergent species including 

Agrostis alba1

 (redtop), Aster novae-angliae (New England 

aster), Eupatorium purpureum (joe pye weed), Eupatorium 

perfoliatum (common boneset), Juncus effusus (soft rush), 

Lobelia cardinalis (cardinal flower), Scirpus cyperinus (wool 

grass), Scirpus validus (great bulrush), and Verbena hastata

(blue vervain) (URS Greiner Woodward Clyde, 1999a). At the 

same time, the SS/FO part was planted with trees and shrubs 

including Acer rubrum (red maple), Quercus palustris (pin 

oak), Quercus bicolor (swamp white oak), Acer saccharinum

(silver maple), Salix nigra (black willow), Viburnum dentatum

(arrowood), Ilex verticillata (winterberry), Cornus amomum

(silky dogwood), Cornus racemosa (gray dogwood), and Cornus stolonifera (red-osier dogwood).

Modified Stream Reach

The modified stream reach is approximately 1 straightline mile north of the wetland-compensation site and lies 

within Valley Forge Park (fig. 1). The reach extends for a 

length of approximately 1,600 ft and has partially wooded 

banks. The channel through this reach generally is free to 

adjust, with few countermeasures that would prohibit lateral 

or vertical migration. The area draining to the downstream 

terminus of the reach is 22.6 mi2

; the underlying lithology is 

1

When plant names are first introduced in the body of this report, the genus 

and species are both spelled out. For subsequent use, the generic names are 

abbreviated, followed by the full species name. When a plant could not be 

identified down to the species level, species is abbreviated with “sp.” When 

referring to multiple species in the same genus, species is abbreviated with 

“spp.”
Introduction 

5

Figure 2. Wetland-compensation site, Tredyffrin Township, Chester County, Pennsylvania. [Plot locations shown in this figure are identified by a four-digit number in the text (0301 for example). The first two numbers represent the transect number (03), and the last two indicate the plot along that transect (01).]

Wetland-compensation siteEnhanced natural wetlandEmergent part of constructed wetlandScrub-shrub/forested part of constructed wetland

BaselineTransect

Sampling plot and number within the constructed wetlandSampling plot and number outside the constructed wetlandPhoto-documentation stationCulvert

PENNSYLVANIA

MONTGOMERYCOUNTY

PHILADELPHIA

CHESTERCOUNTY

TREDYFFRINTOWNSHIP

VALLEY FORGE NATIONAL HISTORICAL PARK 

PHILADELPHIA INTERNATIONAL AIRPORT

WETLAND-COMPENSATION SITE

0 100 FEET

Unnamed

Tributary
6 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

dominated by carbonate bedrock (approximately 68 percent; Pennsylvania Department of Conservation and Natural 

Resources, 2000), and the land use is varied (Price and others, 

2003). Approximately 41 percent of the watershed is used for 

urban development (including high- and low-intensity residential uses and commercial, industrial, and transportation uses), 

and 35 percent is forested (including deciduous, evergreen, 

and mixed-forest types).

Modifications to Valley Creek consist of instream 

stabilization structures and riparian plantings. The stabilization structures were placed at two locations on the right bank 

(as one looks downstream) in the spring of 2001 (fig. 4). The 

downstream structure consists of limestone rock deflectors 

with diameter of about 2 ft aligned in a downstream orientation. The upstream structures consists of two rows of rock 

deflectors aligned in similar fashion, with a fibrous, tubular 

matte at the toe of the bank behind and between the two rows. 

At the upstream location, a nearby swale lined with rip-rap 

conveys runoff to Valley Creek (fig. 4).

Between October and December 2000, trees and shrubs 

were planted in 34 groups of mixed species along the modified 

stream reach (fig. 4). The total number of trees and shrubs was 

dictated by special conditions in project permits that required 

a minimum density of 425 acceptable shrubs or trees per acre 

(planted and acceptable non-planted species). To deter browsing by deer and other herbivores, the groups were enclosed 

by plastic fencing that extended for a height of about 10 ft. 

Species initially planted in 2000 included Ac. rubrum, Ac. saccharinum, Alnus serrulata (smooth alder), Platanus occidentalis (sycamore), Q. palustris, Sal. nigra, Carpinus caroliniana

(ironwood), Clethra alnifolia (summersweet), Co. amomum, 

Co. racemosa, Co. stolonifera, Physocarpus opulifolius (ninebark), and Vi. dentatum.

As a result of plant-replacement guarantees in the project 

contracts, some trees and shrubs that died after planting were 

re-planted in October 2001 and two additional times in 2002. 

The re-planted species included Pl. occidentalis, Sal. nigra, 

Al. serrulata, Cl. alnifolia, Ca. caroliniana, Ac. rubrum, Co. 

stolonifera, Salix discolor (pussy willow), and Co. amomum. 

Cl. alnifolia and Ca. caroliniana were used to replace dead 

Ph. opulifolius plants during the 2002 plantings.

Monitoring Methods

In accordance with project-permit requirements, USGS 

developed and implemented monitoring plans designed to 

quantify changes in 1) the vegetation and soils in the constructed wetland; 2) the profile, dimension, and substrate at 

selected locations along the modified stream reach; and 3) the 

planted and non-planted woody-vegetation communities 

growing within the riparian buffer. The data needed to meet 

these objectives are varied, requiring adaptation of methods 

from multiple sources into a consistent approach. Methods for 

monitoring the wetland largely are from the wetland-delineation manual published by the ACOE Environmental Laboratory (1987) and vegetation sampling protocols described by 

Fitzpatrick and others (1998). The modified stream reach was 

monitored following methods adapted from Rosgen (1996), 

Dunne and Leopold (1978), and Wolman (1954). For the 

riparian buffer, there was no need to select a specific method 

designed to sample a representative portion of the population 

because plants within all pre-defined groups were identified 

and counted.

Many plants generally are easier to identify at the end 

of the growing season (fall), because leaves, stems, and, 

most importantly, reproductive parts are mature. As a result, 

monitoring of each component was scheduled for the fall, with 

the exception of an assessment of the modified stream reach 

in June 2001 to document baseline conditions subsequent to 

installation of rock deflectors. Monitoring of the constructed 

Figure 3. Views of a berm for U.S. Highway 202 (A) and a terrace (A and B) that bound the constructed wetland to the south, 

west, and north.

U.S. Highway 202

Berm

Emergent 

Wetland

October 2000 A B September 2001

Emergent 

Wetland

Terrace

Terrace
Monitoring Methods 

7

Figure 4. Locations of the stabilization structures and riparian plantings within the modified stream reach, Tredyffrin Township, Chester County, Pennsylvania. This figure represents as-built conditions detailed in URS Griener Woodward Clyde (1999a).

0 100 FEET 0 100 FEET

0 100 FEET

Group of planted trees and shrubsand identification number

Foot Bridge

Valley Forge Farm

Covered Bridge

PENNSYLVANIA

MONTGOMERY COUNTY

PHILADELPHIA

CHESTER COUNTY

TREDYFFRIN TOWNSHIP VALLEY FORGE NATIONAL HISTORICAL PARK

Stream Reaches and Riparian Buffer
8 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

wetland began in October 2000 and concluded in September 

2006 (table 1). The riparian buffer was planted between October and December 2000 and was monitored each fall from 

September 2001 to September 2006.

Wetland-Compensation Site

For the purposes of this report, a wetland is defined as an 

area inundated or saturated by water at a frequency and duration sufficient to support a prevalence of vegetation adapted 

for life in saturated-soil conditions (U.S. Army Corps of 

Engineers Environmental Laboratory, 1987). Frequent and (or) 

extended periods of saturation lead to a reducing environment 

that causes chemical reduction of some soil components (like 

iron and manganese oxides). Reducing conditions result in soil 

colors and other physical characteristics indicative of wetland 

or hydric soils. Hydric soils limit the growth of many plants 

but favor hydrophytic species adapted to grow in wetlands. 

Thus, vegetation and soil characteristics, along with evidence 

of frequent and persistent inundation, were used to delineate 

1.36 acres of constructed wetland (0.42 acre of EM wetland 

and 0.94 acre of SS/FO wetland). The extent of the constructed wetland was computed as the area surrounded by the 

delineated boundaries (fig. 2). The boundaries were surveyed 

by standard land-survey techniques using a Nikon DTM 750 

Total Station.

In October 2000, a baseline was established using a 

compass to sight a bearing parallel to the long axis of the 

wetland-compensation site (fig. 2). At this time, five transects 

perpendicular to the baseline were established to create a grid. 

Monumented sampling plots were then established along the 

grid to provide a representative vegetation sample. In fall 

2002, transect number 6 and three additional sampling plots 

(two along transect 3 and one along transect 6; fig. 2) were 

added to the monitoring grid to provide additional representation of emergent and woody vegetation. Throughout this 

report, locations of the sampling plots are described by a fourdigit number (0301, for example) where the first two numbers 

(03) indicate the transect and the last two numbers indicate 

the plot number along that transect (01). The locations of the 

sampling plots that were added to the monitoring grid in fall 

2002 are 0302, 0303, and 0601. Along with the sampling plots, 

six photo-documentation stations were established (fig. 2) in 

October 2000 to provide for visual comparison of site conditions over time. Vegetation, soil, and hydrology data were 

collected by methods described below.

Areal cover of vegetation in the constructed wetland was 

estimated visually within the 16 circular sampling plots (fig. 2) 

having a radius of 15 ft. Plants within the plots were identified 

to species, and their areal cover (expressed as a percentage of 

total plot area), stratum, and indicator status [which reflects 

the range of estimated probabilities of a species occurring in 

wetland areas versus non-wetland areas (Reed, 1988)] were 

determined. Note that total areal cover of vegetation may 

exceed 100 percent because 1) most plant communities consist 

of two or more vegetative strata; 2) areal cover is estimated 

by vegetative stratum; and 3) foliage within a single stratum 

may overlap (U.S. Army Corps of Engineers Environmental 

Laboratory, 1987).

By definition, a plant community growing within a 

wetland is hydrophytic (U.S. Army Corps of Engineers 

Environmental Laboratory, 1987). A vegetation community is 

considered hydrophytic when greater than 50 percent of the 

dominant species have an indicator status of Obligate-wetland 

(OBL), Facultative-wetland (FACW), or Facultative (FAC) 

(U.S. Army Corps of Engineers Environmental Laboratory, 

1987). The indicator status of each identified species in the 

constructed wetland was obtained from the National List of 

Plant Species that Occur in Wetlands Region I–Northeast 

(Reed, 1988). Reed (1988) categorizes plants according to the 

probability that a given species grows in a wetland. OBL species almost always grow solely in wetlands (estimated probability greater than 99 percent). FACW species usually grow 

in wetlands (estimated probability 67–99 percent) but occasionally grow in non-wetlands. FAC species grow in wetlands 

roughly half of the time (estimated probability 34–66 percent). 

Facultative-upland species (FACU) occasionally grow in wetlands (estimated probability 1–33 percent) but usually grow 

in non-wetlands, and Upland species (UPL) grow in nonwetlands. A plus after the category (such as FAC+) indicates 

a frequency of occurrence in the upper end of the probability 

range, whereas a minus indicates a frequency of occurrence in 

the lower end of the range (Tiner, 1999).

Dominant species were determined by the 50/20 rule 

described by the U.S. Army Corps of Engineers Environmental Laboratory (1987). Under this rule, a species can be 

Table 1. Summary of dates for data collection at the constructed wetland and modified stream reach, Tredyffrin Township, Chester 

County, Pennsylvania.

[—, no monitoring]

Monitoring dates

2000 2001 2002 2003 2004 2005 2006

Constructed wetland Oct. 10–11 Sept. 27–28 Sept. 17, 19 Sept. 25 Sept. 7–8 Sept. 6 Sept. 12

Stream channel — June 18, Sept. 10 Sept. 11 Sept. 22 Sept. 10 Sept. 12 Sept. 18

Riparian buffer — Sept. 28 Sept. 18–19, 23 Sept. 26 Sept. 7 Sept. 7 Sept. 13
Monitoring Methods 9

considered dominant at two levels. At the first level, areal 

cover for individual species is compared to 50 percent of the 

total cover. Areal-cover percentages for individual species are 

added, starting with the species providing the most cover and 

working down, until 50 percent of the total cover is equaled 

or exceeded. Those species necessary to exceed 50 percent of 

the total areal cover are considered dominant. At the second 

level, species that did not already qualify as dominant but 

exceed 20 percent of the total areal cover also are considered 

dominant.

Indicators of wetland hydrology, following guidance in 

the ACOE Wetland Delineation Manual (U.S. Army Corps 

of Engineers Environmental Laboratory, 1987), were documented at all sampling plots. Indicators were assessed within 

each sampling plot and include inundation, free water in a 

soil-sampling pit, saturated soils, drainage patterns, and oxidized root channels.

Soil profiles were examined to a depth of at least 12 in., 

or to the depth of refusal, in a soil pit dug within the boundaries of each sampling plot. Soil-matrix color, mottles, texture, 

and structure were determined with Munsell Soil Color Charts 

(Munsell Color, 2000). Each soil horizon was evaluated for 

hydric-soil indicators, which include evidence of histosol 

(organic) or histic epipedon soils, sulfidic odor, aquic moisture regime, gleyed or low-chroma colors, concretions, high 

organic content in the surface layer in sandy soils, and organic 

streaking in sandy soils (U.S. Army Corps of Engineers Environmental Laboratory, 1987). Chroma refers to the strength of 

the soil color (Munsell Color, 2000), and low-chroma colors 

within the “B” horizon are indicative of a fluctuating water 

table that causes periodic chemical reduction (U.S. Army 

Corps of Engineers Environmental Laboratory, 1987).

Stream Reach Surveys

Two discrete reaches of Valley Creek, where rock 

deflectors were installed, were selected for monitoring. These 

reaches are referred to as the upstream reach and downstream reach shown in figure 4. Both sets of rock deflectors 

are intended to protect the adjoining banks from continued 

erosion. Each reach is about 100 ft in length and extends 

beyond the upstream and downstream extent of the deflectors. Surveyed distances are measured along the main flow 

path (thalweg) of the stream. The stream thalweg and water 

surface were surveyed to characterize the profile of the channel within the vicinity of each cross section. For surveys of the 

downstream reach from 2003 to 2006, the channel profile was 

extended farther downstream (compared to surveys in 2001 

and 2002) to better characterize a relatively deep pool. For the 

purposes of this report, right and left sides of the stream channel are determined as if looking downstream. Reported elevations are based on an arbitrary datum and have no relation to 

any other established datum.

For the sake of a uniform comparison, cross-sectional 

channel geometries were determined for the areas bounded by 

re-bar monuments, which were placed beyond the active channel in an attempt to minimize vulnerability to bank erosion. 

The monuments provide definitive end points within which 

evolving channel widths, mean depths, and areas within cross 

sections can be compared. The area bounded by these monuments contains, but is not limited to, the active channel. After 

the fall 2005 assessment and prior to the 2006 assessment, the 

monument marking the right end of the downstream cross section was destroyed as a result of bank erosion. To conform to 

the approach used for previous assessments, the cross-section 

survey was extended just beyond the top of the right bank so 

the geometry of the enlarged channel could be quantified and 

compared to previous assessments. Cross-section locations 

(fig. 4) were selected to define the channel characteristics at 

the point of maximum channel constriction resulting from the 

rock placement. All cross sections are oriented perpendicular 

to the centerline of the channel.

Two 3-ft pieces of reinforcing bar that were 0.5-in. in 

diameter (bank pins) were inserted horizontally into the eroding bank within each cross section until the proximal tip of 

the bar was flush with the bank surface. One bank pin was 

inserted about 1 ft from the base of the streambank, the other 

about 1 ft or 2 ft above. For the upstream cross section, the 

amount of bank recession (erosion) was quantified by the 

amount of the pin exposed between site visits. Bank pins at the 

downstream cross section were lost as a result of bank erosion. 

As a result, the total amount of bank recession (erosion) at this 

cross section was quantified by bank-pin exposure from 2001 

to 2005 plus erosion documented in cross-section surveys 

between 2005 and 2006.

Pebble counts (Wolman, 1954) were conducted to 

quantify the particle distribution within each cross section. 

The quantification of the bed substrate is used to determine 

changes to the material being transported or deposited through 

each reach. Pebble counts do not extend the full distance 

between monuments but are instead confined within fixed 

cross-section end points. Particle distributions are extracted 

from a cumulative frequency curve and reported in a “D#” format where # is the percentage of particles with an intermediate 

axis less than or equal to the reported value.

Photographic documentation was conducted for use 

as a comparative tool between assessments. A minimum of 

five photographs was taken at each cross section to provide 

a visual record of the site during the time of the assessment. Photographic locations for each cross section include 

1) upstream from the cross section looking downstream, 2) 

downstream from the cross section looking upstream, 3) 

standing at the right cross-section monument looking toward 

the left bank, 4) standing at the left cross-section monument 

looking toward the right bank, and 5) the vicinity of the rock 

deflectors.
10 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Riparian Buffer

Most groups of trees and shrubs (fig. 4) were protected 

with deer-exclosure fencing installed according to stream 

enhancement plans developed for PennDOT (URS Greiner 

Woodward Clyde, 1999a). The fencing was intended to 

minimize browsing but not stop it all together. Group 25 was 

intentionally not enclosed with fencing as an informal test 

to determine the amount of browsing by deer on unprotected 

plants. Planted and non-planted trees and shrubs within each 

group were identified and counted by visual inspection. Each 

individual, planted or non-planted, was characterized as alive, 

stressed2

, and (or) browsed3 through visual inspection. Note 

that these categories are not mutually exclusive. For example, 

an individual that is alive but stressed because of browsing 

would be characterized as alive, stressed, and browsed.

Density was determined by dividing the total number 

of individuals in all the groups by the total planted area 

(1.06 acres). The planted area was calculated from the dimension and number of tree and shrub groups in the streamenhancement plans developed by URS Greiner Woodward 

Clyde (1999b). Selected groups were photographed each fall 

to compile a visual record for comparison over time.

Physical and Vegetative Results

Disturbance of wetland and fluvial systems sets the stage 

for dramatic responses—intended or otherwise. For example, 

excavation of the wetland-construction site may expose longdormant yet viable seed banks, in addition to altering preexisting morphology. Application of topsoil and leaf-mulch 

amendments also has the potential to introduce new plant species. Streambank-stabilization features like the rock deflectors 

placed in Valley Creek have little potential for direct effect on 

vegetation; however, they alter flow patterns and may protect the streambanks or accelerate adjustments in the stream 

channel. Planting of riparian buffers along streams commonly 

is attempted to complement countermeasures such as rock 

deflectors (Palone and Todd, 1997; Rosgen, 1996). However, 

climatic conditions during and after planting, along with 

species selection and placement, have a large influence on survival of plants and the ultimate effectiveness of riparian plantings in support of countermeasures. Construction practices in 

the wetland and stream, plant selection, preexisting conditions, 

and climate are all factors that influenced the physical and 

vegetative characteristics discussed in the sections below.

2

Plants that have no foliage, discolored foliage, or malformed fruiting 

structures.

3

Plants damaged from feeding by deer or other herbivores.

Constructed Wetland

When the constructed wetland was first monitored in 

October 2000, differences in vegetation growing in the EM 

and SS/FO parts were more subtle than the distinctions that 

eventually developed. Both parts of the wetland initially were 

dominated by herbaceous communities in fall 2000, despite 

the tree and shrub plantings in the SS/FO part. The herbaceous community persisted in the EM part with some shifts 

in species composition throughout the study. By contrast, a 

thick canopy of trees and shrubs developed by fall 2005 in the 

SS/FO part, allowing only the most shade-tolerant herbaceous 

species to inhabit the understory. Even though vegetation type 

and species composition differed through time, the EM and 

SS/FO parts both supported hydrophytic plant communities 

throughout the study period (table 2). The boundary between 

EM and SS/FO parts also remained consistent.

Areal cover in the EM part ranged from 101 to 

139 percent (fall 2001 and fall 2000, respectively) and was 

135 percent in fall 2006 (table 2). Annual water-level measurements in plots 0301 and 0601 (fig. 5) and hydric-soil indicators (table 3) suggest inundation or soil saturation within 12 in. 

of the soil surface initially was common, even in 2001 and 

2002, a period of severe drought (Northeast Region Climate 

Center, 2007b) (table 4). Frequent and long-lasting saturation 

in the root zone (upper 12 in. of soil) favors OBL species like 

Typha latifolia (broadleaf cattail) and Sc. validus (great bulrush), which maintained dominance in the EM part throughout 

the study (table 2). Sc. validus was the only planted herbaceous species that provided appreciable cover because it was 

best suited to effectively compete with Ty. latifolia (table 2). 

Other planted species either did not germinate or were not able 

to complete with Ty. latifolia and Sc. validus. In fall 2000, the 

end of the first growing season, Sc. validus contributed the 

greatest cover (43 percent), followed by Ty. latifolia (broadleaf 

cattail; 30 percent), Ag. alba (23 percent), Lotus corniculatus (bird’s foot trefiol; 13 percent), and J. effusus (soft rush; 

10 percent). Cover by Sc. validus remained fairly constant for 

5 consecutive years, ranging from 37 to 45 percent between 

2000 and 2004. During this same time frame, cover by 

Ty. latifolia was steadily increasing from 30 percent in 2000 

to 63 percent in 2004 and eventually to 80 and 78 percent in 

2005 and 2006, respectively. Ty. latifolia effectively displaced 

Sc. validus, which contributed only 20 percent cover in the 

last 2 years of the study. Other species in the EM part were 

sparingly present throughout the study, struggling to compete 

with Ty. latifolia and Sc. validus (table 2). By 2006, Impatiens 

capensis (jewelweed) and Agrostis stolonifera (spreading 

bentgrass) were the third and fourth most common species 

contributing 17 and 10 percent areal cover, respectively.

Areal cover in the SS/FO part (table 2) ranged from 

97 percent in 2001 to 146 percent in 2000 and was 139 percent 

in 2006. In 2000 and 2001, the SS/FO part was dominated 

by Echinocloa crusgalli (barnyard grass), an annual invasive 

from Eurasia (Rhoads and Block, 2000) that grew up to 5 ft 

tall. The establishment of Ec. crusgalli is indicative of the 
Physical and Vegetative Results 11

Table 2. Areal cover of vegetation in the constructed wetland, Tredyffrin Township, Chester County, Pennsylvania, 2000–2006.—Continued[NE, Northeast; OBL, obligate-wetland species; FACW, facultative-wetland species; FAC, facultative species; FACU, facultative-upland species; NI, no regional indicator status assigned, UPL, upland species; +, indicates a frequency of occurrence in the upper end of the probability range for that category; -, indicates a frequency of occurrence in the lower end of the probability range for that category; —, not 

observed in constructed wetland sampling plots; shading indicates year or years a particular species was dominant in the emergent or scrub-shrub forested part of the constructed wetland]

Species NE regional 

indicator

Areal cover, in percent

Emergent part Scrub-shrub/forested part

Latin name Common name 2000 2001 2002 2003 2004 2005 2006 2000 2001 2002 2003 2004 2005 2006

Acer saccharinum1 silver maple FACW — — — — — — — — — 1 1 — — —

Agrostis alba1 redtop FACW 23 10 — — — — — 15 18 — — 2 — —

Agrostis stolonifera spreading bentgrass FACW — — — 13 5 8 10 — — 8 18 14 23 21

Alliaria officinalis2 garlic mustard FACU- — — — — — — — — — — 1 — — —

Ambrosia artemisifolia annual ragweed FACU — — — — — — — 1 1 — — — — —

Aster novae-angliae new england aster FACW- — — — — — — — — — — — — — 1

Aster vimineus small white aster FAC — — — — — — — — — — 3 — — —

Bidens frondosa leafy beggar ticks FACW — — — — — — — — 1 1 — — — —

Chenopodium album lamb’s quarters FACU+ — — — — — — — 1 — — — — — —

Cirsium discolor field thistle NI — — — — — — — — — 1 — 1 — 1

Cornus spp.3 dogwood species NI — — — — — — — 1 6 8 2 8 9 13

Cornus stolonifera1,4 red-osier dogwood FACW+ 3 — — — — — — 11 5 5 12 5 2 —

Cyperus strigosus sedge grass FACW — — — — — — — — — — — 1 — 1

Dipsacus sylvestris teasel NI — — — — — — — — 1 3 2 2 — —

Echinocloa crusgalli barnyard grass FACU — — — — — — — 56 25 — — — — —

Eleocharis obtusa spike rush OBL — — — — — — — — — 2 — — — —

Eleocharis sp. spike rush species NI — — — — 3 — — — — 5 4 2 — —

Eupatorium perfoliatum1 common boneset FACW+ 3 3 — — — — — — — — — — — —

Festuca rubra red fescue FACU — 10 10 5 2 2 — — 4 8 2 2 — —

Fraxinus pennsylvanica1 green ash FACW — — — — — — — — — 1 1 — 1 —

Galium sp. bedstraw species NI — — — — — — — — — — 1 — 3 —

Humulus japonicus japonese hops FACU — — — — — — — — — 3 8 7 — 2

Ilex verticillata1 winterberry FACW+ 3 — — — — — — 4 1 — — — — —

Impatiens capensis jewelweed FACW — — 2 — 2 2 17 — — 3 8 8 — —

Juncus effusus1 soft rush OBL 10 — 5 3 — — — — — — — — — —

Juncus tenuis yard rush FAC- — — — — — — — 4 — — — — — —

Lobelia cardinalis1 cardinal flower FACW+ 3 — 2 — — — — — — — — — — —

Lolium perenne perennial rye FACU- — — — — — — — 5 — — — — — —

Lotus corniculatus bird’s foot trefoil FACW+ 13 — — — — — — 4 — — — — — —

Nasturtium officinale watercress OBL — — — — — — — 5 — — 3 10 — 3

Panicum dichotimiflorum witch grass FACW- — — — — — — — 4 — — — — — —

Panicum stipitatum panic grass FACW+ — — — — — — — — — 3 — — — —

Polygonum persicaria lady’s thumb FACW — — — — — — 5 — — — — — — 11

Polygonum sagittatum arrow leaf tearthumb OBL — — — — — — — — — — — — — 1
12 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach Table 2. Areal cover of vegetation in the constructed wetland, Tredyffrin Township, Chester County, Pennsylvania, 2000–2006.—Continued

[NE, Northeast; OBL, obligate-wetland species; FACW, facultative-wetland species; FAC, facultative species; FACU, facultative-upland species; NI, no regional indicator status assigned, UPL, upland species; +, indicates a frequency of occurrence in the upper end of the probability range for that category; -, indicates a frequency of occurrence in the lower end of the probability range for that category; 

—, not 

observed in constructed wetland sampling plots; shading indicates year or years a particular species was dominant in the emergent or scrub-shrub forested part of the constructed wetland]

Species NE regional 

indicator

Areal cover, in percent

Emergent part Scrub-shrub/forested part

Latin name Common name 2000 2001 2002 2003 2004 2005 2006 2000 2001 2002 2003 2004 2005 2006

Polygonum sp. smartweed species NI

—

—

—

—

—

—

— 6 5 3 — 2 —

—

Quercus bicolor1 swamp white oak FACW+

—

—

—

—

—

—

— 1 1 1 1 1 — 2

Rumex crispus curly dock FACU 8 —

—

—

—

—

—

—

—

—

—

—

—

—

Salix nigra1 black willow FACW+

—

—

—

— 3 — 5 6 8 30 36 38 46 48

Sambucus canadensis common elderberry FACW-

—

—

—

—

—

—

—

—

— 1 —

—

—

—

Scirpus atrovirens green bulrush OBL

—

—

—

—

—

—

—

—

— 1 —

—

—

—

Scirpus cyperinus1 wool grass FACW+

—

— 7 —

— 3 —

—

—

— 4 3 5 7

Scirpus validus1 great bulrush OBL 43 45 40 42 37 20 20

—

—

—

—

—

—

—

Setaria faberi foxtail UPL

—

—

—

—

—

—

— 14 6 — 1 —

—

—

Solanum nigrum black nightshade FACU-

—

—

—

—

—

—

—

—

—

— 1 — 2 1

Solidago canadensis canada goldenrod FACU

—

—

—

—

—

—

—

— 1 2 2 — 3 2

Sonchus oleraceus common sow thistle UPL

—

—

—

—

—

—

—

—

— 9 1 —

—

—

Thaspium trifoliatum woodland meadow parsnip NI

—

—

—

—

—

—

—

—

—

—

—

— 1 —

Triodia flava purpletop NI

—

—

—

—

—

—

—

—

—

—

— 1 —

—

Typha latifolia broadleaf cattail OBL 30 33 40 47 63 80 78 8 13 15 25 19 21 17

Urtica dioica stinging nettle FACU

—

—

—

—

—

—

—

—

—

— 2 2 2 5

Vernonia noveboracensis1 new york ironweed FACW

—

—

—

—

—

—

—

—

— 1 —

—

—

—

Viburnum dentatum1 arrowwood FAC

—

—

—

—

—

—

—

— 1 — 2 1 1 3

Cumulative Areal Cover 139 101 106 110 115 115 135 146 97 115 141 129 119 139

1Species was planted. Not all species initially planted in 2000 are listed in this table because some died or did not germinate, and others were only sparingly present outside of established sampling plots.2Synonymous with Alliaria petiolata.3Includes Cornus amomum (silky dogwood) and Cornus racemosa (gray dogwood). Cornus racemosa is synonymous with Cornus foemina.4Synonymous with Cornus sericea.
Physical and Vegetative Results 13

Figure 5. Water levels at sampling plots within the constructed wetland, Tredyffrin Township, Chester County, Pennsylvania, 2000-

2006. [Plot locations are shown on figure 2. The first two numbers of the plot location (0301, for example) represent the transect 

number (03), and the last two indicate the plot along that transect (01).] DEPTH OF, OR DEPTH TO WATER WITH RESPECT TO GROUND SURFACE, IN INCHES

EXPLANATION

2000

2001

2002

2003

2004

2005

2006

2000

2001

2002

2003

2004

2005

2006

2000

2001

2002

2003

2004

2005

2006

2000

2001

2002

2003

2004

2005

2006

2000

2001

2002

2003

2004

2005

2006

2000

2001

2002

2003

2004

2005

2006

PLOT 0103 SS/FO PLOT 0202 SS/FO

PLOT 0301 SS/FO PLOT 0401 SS/FO

PLOT 0402 SS/FO PLOT 0502 EM

0

-5

-10

-15

-20

5

0

-5

-10

-15

-20

5

0

-5

-10

-15

-20

5

PLOT 0302 EM

NO

DATA

PLOT 0303 SS/FO

NO

DATA

PLOT 0601 EM

NO

DATA

DEPTH TO WATER BELOW GROUND SURFACE

DEPTH OF WATER ABOVE GROUND SURFACE 

INDICATES DEPTH OF WATER IS GREATER

INDICATES WATER LEVEL IS DEEPER BELOW GROUND 

GROUND SURFACE

PLOT IS WITHIN THE SCRUB-SHRUB/FORESTED PART 

 OF THE CONSTRUCTED WETLAND

SS/FO

EM PLOT IS WITHIN THE EMERGENT PART OF THE 

 CONSTRUCTED WETLAND
14 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

disturbed site conditions that initially existed after construction. Some planted and non-planted woody species also were 

present at this time, including Sal. nigra and Cornus spp.

Sal. nigra favored areas that had consistent hydric-soil indicators (table 3) in the vicinity of plots 0302, 0303, 0402, and 

0502. Cornus spp. (dogwood species) generally was established in and around plots 0103 and 0202, which seemed to 

have infrequently saturated soils (fig. 5) and less consistent 

hydric-soil indicators (table 3). By fall of 2002, Ec. crusgalli

was not growing in any of the sample plots, and other herbaceous [Ag. stolonifera and Festuca rubra (red fescue)] and 

woody (Cornus spp. and Sal. nigra) species became more 

common (table 2). Sal. nigra contributed 30-percent cover 

by fall 2002 and continued to increase through 2006. By fall 

2006, 15 to 25 ft tall Sal. nigra trees and 4 to 8 ft Cornus spp.

shrubs dominated the tree/shrub stratum [48 and 13 percent 

of the areal cover, respectively (table 2)], and much of the 

understory was shaded. This left shade-intolerant species at 

a competitive disadvantage. For example, Q. bicolor and Vi. 

dentatum contributed only 2- and 3-percent areal cover in fall 

2006, and Ac. saccharinum, which provided 1-percent cover in 

fall 2002 and fall 2003, was not observed during the remainder 

of the study. By 2006, some non-planted species including 

Populus deltoides (cottonwood) and Betula sp. began to establish around the margins of the SS/FO part and in the enhanced 

natural wetland. These trees were growing outside of established sampling plots.

Ag. stolonifera and Ty. latifolia were dominant components of the herbaceous understory in the SS/FO part by 2006 

(21- and 17-percent areal cover, respectively). Ag. stolonifera favored the shaded areas and Ty. latifolia grew near the 

margins of the SS/ FO part where more sunlight was available. Other notable herbaceous species that were observed at 

the end of monitoring in 2006 include Polygonum persicaria

(lady’s thumb; 11-percent areal cover), Sc. cyperinus (wool 

grass; 7-percent areal cover) and Urtica dioica (stinging nettle; 

5-percent areal cover). Nasturtium officinale (Watercress), 

which contributed 10-percent areal cover and was a dominant 

species in fall 2004, was not observed in fall 2005 and contributed only 3-percent areal cover in fall 2006.

Various invasive species were observed throughout the 

study period but did not seem to be affecting the ability of 

native species to establish and dominate the site. Dipsacus 

sylvestris (teasel), a tall biennial native to Europe, Humulus 

japonicus (japanese hops), a creeping vine native to Asia, 

and Ec. crusgalli, a grass native to Eurasia, were the most 

prevalent invasive species (table 2). In fall 2006, H. japonicus

Table 3. Observations of hydric-soil indicators in the constructed wetland, Tredyffrin Township, Chester County, Pennsylvania, 

2000–2006.

[SS/FO, scrub-shrub/forested; EM, emergent; ND, no data collected; shading denotes hydric-soil indicators were present]

Plot1 Designation2 2000 2001 2002 2003 2004 2005 2006

0103 SS/FO

0202 SS/FO

0302 SS/FO ND ND

0303 SS/FO ND ND

0402 SS/FO

0502 SS/FO

0301 EM

0401 EM

0601 EM ND ND 1

Plot locations are shown on figure 2. The first two numbers of the plot location (0301, for example) represent the transect number (03) and the last two 

indicate the plot along that transect (01).

2

In September 2000, areas of the constructed wetland planted with an abundance of trees and shrubs were designated scrub-shrub/forested (SS/FO) and areas 

planted with emergent vegetation were designated EM. The boundaries of these areas are shown in figure 2.

Table 4. Cumulative precipitation measured at Valley Forge 

National Historical Park for water years 2000–2006, Montgomery 

County, Pennsylvania.

Water year1

Cumulative

precipitation

(inches)2

Departure from

30-year mean

(1971-2000)

(inches)3

2001 35.35 -6.70

2002 30.50 -11.55

2003 71.66 29.61

2004 59.75 17.70

2005 40.10 -1.95

2006 54.31 12.26

1

Water year is the 12-month period October 1 through September 30. The 

water year is designated by the calendar year in which it ends and which 

includes 9 of the 12 months.

2

Data from Northeast Regional Climate Center (2007a).

3

30-year mean of 42.05 inches was measured at Philadelphia International 

Airport (Northeast Regional Climate Center, 2007a).
Physical and Vegetative Results 15

contributed 2-percent areal cover, but other invasives listed 

above were not observed. It is assumed that work efforts completed by PennDOT during 3 of the 7 years (03, 04, and 06) to 

manually remove H. japonicus played a role in controlling the 

spread of this species.

Stream Channel

In spring 2001, PennDOT installed rock deflectors within 

Valley Creek to mitigate selected locations exhibiting active 

streambank erosion. The response of the channel following 

installation of the structures is a direct function of structure 

characteristics, channel morphology, and hydrologic conditions to which the modified stream channel was subjected. 

From June 2001 through September 2006, two reaches of the 

channel (see upstream and downstream reaches in figure 4) 

were monitored annually (see table 1 for dates of monitoring) to document changes at least partially attributable to this 

mitigation effort.

Hydrologic Conditions

The streamflow-gaging station at Valley Creek at Pennsylvania Turnpike Bridge near Valley Forge, Pa. (fig. 1), has 

been in operation since October 1982. This gaging station is 

useful for characterizing the hydrologic conditions between 

annual monitoring assessments and for placing the monitoring data within the context of a period of record in excess of 

20 years.

Data used for the hydrologic characterization were 

collected during the 2001–06 monitoring period (Durlin 

and Schaffstall, 2001–2005; Durlin and others, 2006; U.S. 

Geological Survey, 2007). The annual mean streamflow for 

the period of record ending water year4

 2006 was 33.5 ft3/s. 

Annual mean streamflow during the period the modified 

stream reach was monitored ranged from 15.2 ft3

/s in the 2002 

water year to 53.0 ft3

/s in the 2004 water year. This is a range 

of about 55 percent lower to 58 percent higher than the annual 

mean streamflow for the period of record. Maximum annual 

instantaneous streamflows, during the monitoring period, 

ranged from 576 (June 6, 2002) to 2,730 ft3

/s (September 28, 

2004). During the monitoring period, 19 separate storms had 

streamflows with recurrence intervals of 1.5 years or greater 

(probabilities of exceedance of 67 percent or less). Streamflows with recurrence intervals of 1–2 years (1.5 years on 

average) commonly are considered to be the most effective or 

dominant channel-forming flows (Dunne and Leopold, 1978). 

The highest streamflow for the period of record at the Valley 

Creek streamflow-gaging station is 6,280 ft3

/s on September 

16, 1999.

4

Water year is the 12-month period October 1 through September 30. The 

water year is designated by the calendar year in which it ends and which 

includes 9 of the 12 months.

Changes to the Channel

The slope of a stream channel is one of several key factors in determining sediment transport. An increasing channel 

slope and associated increasing stream velocity may increase 

the particle size the channel can transport during a given 

flow and result in a coarsening of bed material; conversely, a 

decreasing slope may reduce transport and cause a decrease in 

particle size.

Elevations surveyed throughout fixed distances upstream 

and downstream from each cross section shown in figure 2 

were used to compute water surface and streambed slopes 

at the upstream and downstream reaches of the modified 

stream channel (tables 5 and 6). The extent of each reach was 

intended to isolate the portion of the channel in the immediate vicinity of a rock deflector and to document the resulting 

channel response.

Water-surface and streambed slopes at the two reaches 

(shown in figure 2) remained relatively stable during the monitoring period, ranging from 0.01 to 0.02 ft/ft in the upstream 

reach (table 5) and 0.01 to 0.04 ft/ft in the downstream reach 

(table 6) with no more than ± 0.01 ft/ft variation compared 

to the initial conditions established in June 2001. The minor 

slope fluctuations noted between annual surveys of the 

longitudinal profiles are not considered to be appreciable and, 

in many cases, are primarily the result of mathematical rounding in the slope computation. Changes in stationing, length 

of reach or riffle, or in the actual positions of distinct channel 

features are, in most cases, attributed to inconsistent placement 

of the measuring tape rather than changes to the reach profiles. 

Variations in the appearance of the upstream and downstream 

profiles, as displayed in figures 6 and 7, are evidence of 

slight deposition or erosion within the reaches and, in most 

instances, are considered more a function of transient material 

passing through the reaches than an actual lasting change. One 

possible exception is the apparent accumulation of material 

in the pool at the downstream reach in the vicinity of station 115 during the 2006 assessment. Continued monitoring 

over a range of hydrologic conditions would be necessary to 

determine if this was a change in the sediment transport of the 

reach or a temporary characteristic as displayed near station 70 

in the 2002 profile. The overall consistency of the reach 

slopes is most likely because of the presence of bedrock at the 

streambed (visibly cropping out around stations 70-90 in the 

upstream reach) prohibiting downcutting of the channel and 

the presence of sufficient energy within the system to transport 

the material supplied to each reach.

Sequences of deeper pools with slow-flowing water and 

shallow riffles with higher-velocity flow provide physical 

habitat composed of a great diversity of bed forms, substrate 

materials, and local velocities capable of supporting biotic 

diversity (Gordon and others, 1992). Over the monitoring 

period, the extent of the riffle and pools composing each reach 

stayed relatively constant; the length of the riffle remained 

within 4 percent of the June 2001 length.
16 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Table 5. Longitudinal profile characteristics of the upstream reach of the modified stream channel, Tredyffrin Township, Chester 

County, Pennsylvania.

[ft, feet]

Profile characteristics June

2001

Sept. 

2002

Sept. 

2003

Sept.

2004

Sept.

2005

Sept.

2006

Change, in percent

2001–

2002

2001–

2003

2001–

2004

2001–

2005

2001–

2006

Reach water-surface slope (ft/ft) 0.01 0.01 0.01 0.01 0.01 0.01 0 0 0 0 0

Reach length (ft) 90.0 90.0 90.0 90.0 90.0 90.0 0 0 0 0 0

Reach bed slope (ft/ft) .02 .01 .01 .01 .01 .01 -50 -50 -50 -50 -50

Riffle water-surface slope (ft/ft) .01 .02 .01 .01 .01 .01 100 0 0 0 0

Riffle bed slope (ft/ft) .02 .02 .02 .02 .02 .02 0 0 0 0 0

Riffle length (ft) 38.5 38.0 38.0 38.0 38.0 38.0 -1 -1 -1 -1 -1

Table 6. Longitudinal profile characteristics of the downstream reach of the modified stream channel, Tredyffrin Township, Chester 

County, Pennsylvania.

[ft, feet]

Profile characteristics June 

2001

Sept. 

2002

Sept. 

2003

Sept. 

2004

Sept. 

2005

Sept. 

2006

Change, in percent

2001–

2002

2001–

2003

2001–

2004

2001–

2005

2001–

2006

Reach water-surface slope (ft/ft) 0.01 0.01 0.01 0.01 0.01 0.01 0 0 0 0 0

Reach length (ft) 70.0 73.0 73.0 73.0 73.0 73.0 4 4 4 4 4

Reach bed slope (ft/ft) .03 .03 .02 .02 .04 .02 0 -33 -33 33 -33

Riffle water-surface slope (ft/ft) .01 .01 .01 .01 .01 .01 0 0 0 0 0

Riffle bed slope (ft/ft) .02 .02 .02 .02 .02 .02 0 0 0 0 0

Riffle length (ft) 58.0 60.6 60.6 60.6 60.6 60.6 4 4 4 4 4
Physical and Vegetative Results 17 Figure 6. Longitudinal profile of the upstream reach of the modified stream reach, Tredyffrin Township, Chester County, Pennsylvania. [Annual discrepancies in stationing along the longitudinal profile are because of changes in the thalweg and the resulting inability to place the measuring tape along the exact same path.]

WATER SURFACE FALL 2006THALWEG FALL 2006THALWEG FALL 2005THALWEG FALL 2004THALWEG FALL 2003THALWEG FALL 2002THALWEG JUNE 2001

CROSS-SECTION LOCATION

DISTANCE DOWNSTREAM FROM STARTING POINT OF SURVEY, IN FEET

ELEVATION ABOVE ARBITRARY DATUM, IN FEET

86.586.085.585.084.584.083.583.0

0 10 20 30 40 50 60 70 80 90 100
18 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach Figure 7. Longitudinal profile of the downstream reach of the modified stream reach, Tredyffrin Township, Chester County, Pennsylvania.

[Annual discrepancies in stationing along the longitudinal profile are because of changes in the thalweg and the resulting inability to place the measuring tape along the exact same path.]

CROSS-SECTION LOCATION

WATER SURFACE FALL 2006THALWEG FALL 2006THALWEG FALL 2005THALWEG FALL 2004THALWEG FALL 2003THALWEG FALL 2002THALWEG JUNE 2001

ELEVATION ABOVE ARBITRARY DATUM, IN FEET

78.578.077.577.076.576.075.575.074.574.073.573.072.572.0

DISTANCE DOWNSTREAM FROM STARTING POINT OF SURVEY, IN FEET

0 20 40 60 80 100 120 140
Physical and Vegetative Results 19

Changes in width, mean and maximum depth, and area of 

a cross section are indications of the degree to which a channel 

is adjusting. The stream channel will continue to adjust until 

it reaches dynamic equilibrium, a condition that exists when 

the stream channel is capable of conveying the streamflow 

and sediment load being supplied without excessive erosion or 

deposition that may lead to changes in channel morphology.

Since monitoring began in June 2001, the cross section in 

the upstream reach experienced changes in channel morphology in the 1–3 percent range; the one exception was maximum 

depth, which decreased by 6 to 9 percent over the monitoring period when compared to the June 2001 survey (table 7). 

Removing one 2001 isolated survey point in the active channel 

near station 48 from consideration results in an overall change 

of about 3 percent during the monitoring period, more in line 

with the other parameters. A notable feature in the 2001 and 

2002 survey (fig. 8) is the inclusion of a tree on the left bank 

that was no longer present during subsequent surveys. Streambank erosion in the upstream reach, measured as a result of 

exposure of bank pins, was a maximum of 0.8 ft over the 

monitoring period.

The cross section in the downstream reach experienced 

notable channel enlargement over the monitoring period as 

a result of erosion of the right streambank. Relatively stable 

over the first 3 years of monitoring, the 2005 assessment 

documented 9 percent increases in both cross-sectional area 

and mean cross-section depth due, in part, to erosion of the 

right bank (bank pins indicated an average of 0.86 ft of bank 

erosion) as well as the cutting of a secondary channel on 

the left bank and slight bed erosion. Distance from the right 

streambank to the landward-most rock of the deflector (which 

is upstream from the surveyed cross section) was about 3 ft in 

2005, thus decreasing the protection of the bank and quite possibly exacerbating the erosion by directing accelerated flow 

into the “toe” of the bank. Over the following year, substantial 

bank retreat was evident; cross-sectional area increased by 

33 ft2

 (13 percent) between 2005 and 2006 for a total increase 

of 54 ft2

 (23 percent) over the entire monitoring period. The 

monument on the right bank marking the extent of the surveyed cross section and both bank pins (used to quantify bank 

retreat) were destroyed as a result of 8.0 ft of bank erosion that 

occurred between fall 2005 and fall 2006 (fig. 9). Cumulative 

bank erosion, as measured with bank pins and cross-section 

surveys, was greater than 10 ft over the entire monitoring 

period. As a result of the erosion noted during the 2006 assessment, the distance between the right bank and the landwardmost rock in the deflector was about 14 ft, essentially leaving 

the rock deflectors in mid-stream where they provided no 

protection of the bank. As indicated by the change in channel 

morphology at the downstream reach it is apparent that the 

rock deflectors were ineffective at adequately protecting the 

bank from erosion.

The particle distribution of a stream is indicative of the 

sediment load being supplied to the system as well as the 

ability of the stream to transport it. The coarser the sediment, 

the more energy required to transport it. On the basis of the 

median particle-size category (D50), as determined during 

pebble counts for both cross sections throughout the monitoring period, Valley Creek can be characterized as a gravel-bed 

stream.

Particle distributions in the upstream reach, determined 

during the June 2001 assessment, tended to be notably coarser 

than in the subsequent four assessments (table 7 and fig. 10). 

Particle distributions in the upstream reach decreased throughout all distribution categories through the 2005 assessment 

when compared to the results of the June 2001 assessment. An 

Table 7. Cross-section dimensions and bed-particle-size distribution in the upstream reach, Tredyffrin Township, Chester County, 

Pennsylvania.

[D15, 15th percentile bed-particle size; D35, 35th percentile bed-particle size; D50, 50th percentile bed-particle size; D84, 84th percentile bed-particle size; D95, 

95th percentile bed-particle size; <, less than]

Profile characteristics June 

2001

Sept. 

2002

Sept. 

2003

Sept. 

2004

Sept. 

2005

Sept. 

2006

Change, in percent

2001–

2002

2001–

2003

2001–

2004

2001–

2005

2001–

2006

Flow regime: Riffle Riffle Riffle Riffle Riffle Riffle

Cross-section area, in square feet 202 197 202 200 200 205 -2 0 -1 -1 1

Baseline width, in feet 74.0 74.2 74.0 74.2 74.2 74.2 <1 0 <1 <1 <1

Mean cross-section depth, in feet 2.74 2.66 2.72 2.70 2.69 2.77 -3 -1 -1 -2 1

Maximum cross-section depth, in feet 6.08 5.52 5.54 5.70 5.60 5.63 -9 -9 -6 -8 -7

Pebble count, in millimeters:

D15 3.0 1.1 2.2 2.6 1.3 3.7 -63 -27 -13 -57 23

D35 22.1 8.8 12.2 7.1 8.7 52 -60 -45 -68 -61 135

D50 56.3 21.4 33.7 19.6 26.9 86 -62 -40 -65 -52 53

D84 199 173 128 184 148 187 -13 -36 -8 -26 -6

D95 407 314 252 391 233 293 -23 -38 -4 -43 -28
20 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Figure 8. Surveys of the upstream cross section of the modified stream reach, Tredyffrin Township, Chester County, Pennsylvania.

BASELINE

BED AND BANK SURFACE FALL 2006

BED AND BANK SURFACE FALL 2005

BED AND BANK SURFACE FALL 2004

BED AND BANK SURFACE FALL 2003

BED AND BANK SURFACE FALL 2002

BED AND BANK SURFACE JUNE 2001

FALLEN TREE 

ELEVATION ABOVE ARBITRARY DATUM, IN FEET 

92

91

90

89

88

87

86

85

84

83

DISTANCE FROM MONUMENT ON LEFT BANK, IN FEET

0 10 20 30 40 50 60 70 80
Physical and Vegetative Results 21

Figure 9. Surveys of the downstream cross section of the modified stream reach, Tredyffrin Township, Chester County, 

Pennsylvania.

BASELINE

BED AND BANK SURFACE FALL 2006

BED AND BANK SURFACE FALL 2005

BED AND BANK SURFACE FALL 2004

BED AND BANK SURFACE FALL 2003

BED AND BANK SURFACE FALL 2002

BED AND BANK SURFACE JUNE 2001

DISTANCE FROM MONUMENT ON LEFT BANK, IN FEET

0 10 20 30 40 50 60 70 80 90

ELEVATION ABOVE ARBITRARY DATUM, IN FEET

83

82

81

80

79

78

77

76

75
22 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach Figure 10. Comparison of particle-size distributions in the upstream cross section, 2001–2006.

0

908070605040302010

100

June 2001

Sept. 2002

Sept. 2003

Sept. 2004Sept. 2005

Sept. 2006

mm 652mm 46 mm 2 0.062

BOULDERS

COBBLES

GRAVEL

SILT

SAND

PARTICLE SIZE, IN MILLIMETERS

PERCENT FINER THAN

0.01 0.1 1 10 100 1,000 10,000
Physical and Vegetative Results 23

average decrease of about 50 percent was noted in the D15 to 

D50 distribution categories, tending to be composed of coarse 

gravels. The average particle size for the D50 category, among 

all assessments, was 41 mm. The D84 and D95 categories 

decreased in size by an average of 24 percent and were characterized by cobbles and boulders. The pebble count during 

the 2006 assessment indicated a reversal of the previous trend 

toward smaller particles in the D15 to D50 categories, resulting, on average, in a 70-percent increase in particle sizes, still 

primarily gravels but noticeably coarser. The coarsening of the 

material in these size categories is most likely indicative of 

the load being carried by preceding storms and the continued 

capability of this reach to transport a majority of the material 

being provided. The D84 and D95 categories continued to be 

smaller than during the June 2001 assessment.

Particle distributions in the cross section in the downstream reach generally decreased in size in all categories and 

for all assessments with only two exceptions (table 8 and 

fig. 11). Similar to the upstream reach, an average decrease 

of about 50 percent was noted in the D15 to D50 distribution categories; most particles were characterized as coarse 

gravels. The average particle size for the D50 category, among 

all assessments, was 22 mm. The D84 and D95 categories 

decreased in size over the monitoring period by an average 

of 22 percent and were characterized by cobbles. Unlike the 

upstream reach, particle distributions in all size distributions, 

except the D95, decreased in size in 2006. The continued presence of finer material within the cross section, when compared 

to the June 2001 assessment, suggests a decrease in the sediment transport of this reach. This is commonly the case when 

a channel is actively widening, resulting in decreasing depths 

of streamflow which, in turn, decreases the ability of the 

stream to transport sediment.

Riparian Buffer

Because of the replacement plantings in 2001 and 2002, 

the most reliable time frame for interpretation of trends in the 

number and condition of riparian plantings is 2003–2006. The 

most prevalent planted tree species that was surviving in 2003 

was Pl. occidentalis (63 individuals), followed by Ca. caroliniana (35), Q. palustris (33), Al. serrulata (30), Ac. rubrum

(26), Ac. saccharinum (17), and Sal. nigra (10) (fig. 12). 

The most prevalent shrubs in 2003 were Cornus spp. (dogwood species; 98 individuals), followed by Sa. discolor (51), 

Ph. opulifolius and V. dentatum (28), Cl. alnifolia (27), and 

Sp. virginiana (4). Drought conditions in the fall of 2001 and 

throughout 2002 (Northeast Regional Climate Center, 2007b) 

may have been the primary cause of stress or death in newly 

planted trees and shrubs and could have had prolonged effects 

lasting throughout the study.

A large percentage of trees and shrubs remained stressed 

in 2003 including Q. palustris (65 percent), Al. serrulata

(36 percent), Ac. rubrum (34 percent), and Sa. discolor

(57 percent) (fig. 13) despite higher than average precipitation in the summer months of 2003 (Northeast Regional 

Climate Center, 2007a; table 4). Trees and shrubs that appreciably declined in number between 2003 and 2006 [including 

Sal. nigra, Alnus serrulata, Ac. saccharinum, Sa. discolor, and 

Cl. alnifolia (fig. 12)] generally exhibited more stress in 2003 

(fig. 13) compared to their counterparts that remained nearly 

constant or increased in number throughout the study (fig. 12). 

Note that year-to-year decreases in the percentage of stressed 

individuals over time does not necessarily indicate improvement in the overall well being of the original plantings. For 

example, the percentage of stressed plants in a given year may 

Table 8. Cross-section dimensions and bed-particle-size distribution in the downstream reach, Tredyffrin Township, Chester County, 

Pennsylvania.

[D15, 15th percentile bed-particle size; D35, 35th percentile bed-particle size; D50, 50th percentile bed-particle size; D84, 84th percentile bed-particle size; D95, 

95th percentile bed-particle size; NC, not computed because percentage of smallest particles in 2002 assessment exceeded 15 percent; <, less than]

Profile characteristics June 

2001

Sept. 

2002

Sept. 

2003

Sept. 

2004

Sept. 

2005

Sept. 

2006

Change, in percent

2001–

2002

2001–

2003

2001–

2004

2001–

2005

2001–

2006

Flow regime: Riffle Riffle Riffle Riffle Riffle Riffle

Cross-section area, in square feet 237 236 237 241 258 291 <-1 0 2 9 23

Baseline width, in feet 72.0 72.0 71.6 71.6 71.6 80.2 0 <-1 <-1 <-1 11

Mean cross-section depth, in feet 3.29 3.28 3.31 3.37 3.60 3.63 <-1 1 2 9 10

Maximum cross-section depth, in feet 6.02 6.46 6.29 6.25 6.29 6.35 7 4 4 4 5

Pebble count, in millimeters:

D15 6.3 NC 4.0 1.2 1.3 1.8 NC -37 -81 -79 -71

D35 17.0 1.2 15.3 5.8 5.4 10.6 -93 -10 -66 -68 -38

D50 34.2 8.0 36.3 14.6 11.6 27.7 -77 6 -57 -66 -19

D84 114 73.3 84.7 67.2 73.3 105 -36 -26 -41 -36 -8

D95 176 146 139 156 120 191 -17 -21 -11 -32 9
24 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Figure 11. Comparison of particle-size distributions in the downstream cross section, 2001–2006.

June 2001

Sept. 2002

Sept. 2003

Sept. 2004

Sept. 2005

Sept. 2006

Silt

0

908070605040302010

100

mm 652mm 46 mm 2 0.062

BOULDERS

COBBLES

GRAVEL

SILT

SAND

PARTICLE SIZE, IN MILLIMETERS

PERCENT FINER THAN

0.01 0.1 1 10 100 1,000 10,000
Physical and Vegetative Results 25 Figure 12. Number of planted trees (A) and shrubs (B) growing in the riparian buffer, Tredyffrin Township, Chester County, Pennsylvania, 2001–2006.

[Platanus occidentalis (sycamore), Salix nigra (black willow), Alnus serrulata (smooth alder), Clethra alnifolia (summersweet), and Carpinus caroliniana (ironwood) individuals that died during the 2001 growing season were replaced shortly after data collection in 2001 (October 2001). Additional trees and shrubs of the following species were replanted at various times before 

and after monitoring in 2002: Cl. alnifolia, Ca. caroliniana, Pl. occidentalis, Acer rubrum (red maple), Cornus spp. (dogwood 

species), Salix discolor (pussy willow), Sal. nigra, and Al. serrulata.]

NUMBER OF PLANTED TREES THAT SURVIVED NUMBER OF PLANTED SHRUBS THAT SURVIVED Viburnum dentatum Spirea virginiana Salix discolor Physiocarpus opulifolius Cornus spp. Clethera alnifolia EXPLANATION 600 500 400 300 200 100

0

2001 2002 2003 2004 2005 2006

2001 2002 2003 2004 2005 2006

250200150100

50

0

Salix nigraQuercus palustrisPlatanus occidentalisCarpinus carolinianaAlnus serrulataAcer saccharinumAcer rubrum 

EXPLANATION

AB
26 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Figure 13. Percentage of planted species of trees (A) and shrubs (B) in the riparian buffer that were stressed, Tredyffrin Township, 

Chester County, Pennsylvania, 2001–2006.

[Year-to-year decreases in the percentage of stressed individuals over time may not indicate improvement in the overall well-being of a given species. For example, 

the percentage of stressed plants in a given year may decrease because the weakest plants died the year before, leaving only the healthiest, least-stresssed plants.]

Acer

rubrum

Acer

saccharinum

Alnus

serrulata

Carpinus

caroliniana

Platanus

occidentalis

Quercus

palustris

Salix

nigra

0

20

40

60

80

100

STRESSED TREES, IN PERCENT

SPECIES

01 02 03 04 05 06 02 03 04 05 01 06 02 03 04 05 01 06 02 03 04 05 01 06 02 03 04 05 01 06 02 03 04 05 01 06 02 03 04 05 01 06

Clethera

alnifolia

Cornus

spp.

Physiocarpus

opulifolius

Salix

discolor

Spirea

virginiana

Viburnum

dentatum

0

20

40

60

80

100

STRESSED TREES, IN PERCENT

SPECIES

01 02 03 04 05 06 02 03 04 05 01 06 02 03 04 05 01 06 02 03 04 05 01 06 02 03 04 05 01 06 02 03 04 05 01 06

A

B
Physical and Vegetative Results 27

decrease because the weakest plants died the year before, leaving only the healthiest, least-stressed plants.

In the year preceding fall 2006 monitoring, infrequent but 

debris-laden overbank flows breached some of the exclosure 

fences, allowing deer and other herbivores uninhibited access. 

Data collected in fall 2006 indicate herbivores preferred to 

browse planted species rather than non-planted vegetation 

(table 9). As a result, 23 percent of planted species were 

browsed and 17 percent were stressed in 2006 (table 9). By 

contrast, none of the non-planted species were browsed, and 

only 7 percent exhibited signs of stress (table 9). Browsing 

was most common among the planted shrub species; greater 

than 25 percent of Cornus spp., Cl. alnifolia, V. dentatum, and 

Sa. discolor plants were browsed. This is presumably because 

the shrubs were smaller (4–8 ft tall) and more accessible by 

deer; trees in most groups were 10–20 ft tall in 2006 except for 

Pl. occidentalis, which ranged from 15 to 30 ft tall.

Dissimilarities in the incidence of browsing and stress 

among these species contributed to a decrease in the number 

of planted trees and shrubs and an increase in the number 

of surviving non-planted plants between 2001 and 2006. 

Despite replacement of dead individuals in 2001 and 2002, 

planted trees decreased from 214 in 2001 to 171 in 2006 

(fig. 12A) and shrubs decreased from 546 in 2001 to 225 in 

2006 (fig. 12B). By contrast, the cumulative number of the 

two most prevalent non-planted species [Acer negundo (box 

elder) and Gymnocladus dioicus (Kentucky coffee tree)] more 

than doubled over the same time period (from 110 to 244 

plants) (fig. 14). These two species are native to Pennsylvania 

(Rhoads and Block, 2000) and were most prevalent in group 

numbers 1 (Ac. negundo and Gy. dioicus), 18, 28, and 34 

(Ac. negundo), at the end of the study. The density of planted 

species at the end of the study was 382 plants per acre compared to 329 plants per acre for non-planted species (table 9). 

Although decreases in the number of planted individuals were 

appreciable, the remaining plants grew substantially in most 

groups, often achieving canopy closure (see photographs in 

figures 5-2 through 5-11 in appendix 5).

Data collected in 2006 indicate non-native plant species 

could be the greatest future threat to woody vegetation growing in planted areas of the riparian buffer. Lonicera spp. (honeysuckle species), including two bush species native to Japan, 

were found in groups 5, 6, and 7 in 2006. Humulus japonicus, 

a creeping herbaceous vine native to Asia is ubiquitous; it was 

growing in groups 1, 2, 6, 7, 21, 22, 23, 25, 29, 31, and 34. 

Polygonum perfoliatum, a climbing vine from Asia commonly 

called mile-a-minute-weed, was found in plots 1, 7, 18, 20, 

22, 30, and 33. These species have a tendency to displace, 

smother, or otherwise out-compete native species if not kept in 

check.

COUNT

Gymnocladus dioicus

Acer negundo

0

50

100

150

200

250

300

2001 2002 2003 2004 2005 2006

EXPLANATION

Figure 14. Number of Acer negundo (box elder) and Gymnocladus dioicus (Kentucky coffee tree) plants 

growing in the riparian buffer, Tredyffrim Township, Chester County, Pa., 2001–2006.
28 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Table 9. Woody trees and shrubs growing in the riparian buffer, fall 2006.

[%, percent; shading indicates the species is a tree, no shading indicates the species is a shrub]

Species

Alive

Stressed1 Browsed2 Density 

(plants per 

acre) Latin Name Common Name % Count % Count 3

Acer negundo box elder 134 13 18 0 0 126

Acer rubrum4 red maple 34 15 5 0 0 32

Acer saccharinum4 silver maple 1 100 1 0 0 1

Alnus serrulata4 smooth alder 17 12 2 0 0 16

Carpinus caroliniana4 ironwood 33 3 1 0 0 31

Clethra alnifolia4 summersweet 3 33 1 33 1 3

Cornus spp.4 dogwood species 169 11 19 47 82 159

Fraxinus pennsylvanica green ash 32 9 3 0 0 30

Gleditsia triacanthos honey locust 16 0 0 0 0 15

Gymnocladus dioicus kentucky coffee-tree 110 0 0 0 0 104

Hibiscus syriacus rose of sharon 1 0 0 0 0 1

Juglans nigra Black Walnut 12 0 0 0 0 11

Ligustrum vulgare european privet 2 0 0 0 0 2

Lindera benzoin spicebush 9 0 0 0 0 8

Liriodendron tulipifera tulip tree 1 100 1 0 0 1

Lonicera sp. honeysuckle 25 0 0 0 0 24

Maclura pomifera osage-orange 1 0 0 0 0 1

Physocarpus opulifolius4 ninebark 22 5 1 0 0 21

Platanus occidentalis4 sycamore 57 5 3 0 0 54

Prunus serotina black cherry 2 0 0 0 0 2

Quercus palustris4 pin oak 29 90 26 0 0 27

Quercus rubra red oak 2 50 1 0 0 2

Quercus sp. oak species 1 0 0 0 0 1

Salix discolor4 pussy willow 11 45 5 27 3 10

Salix nigra4 black willow 3 0 0 0 0 3

Spirea virginiana4 Virginia spirea 2 0 0 0 0 2

Ulmus americana American elm 1 0 0 0 0 1

Viburnum dentatum4 arrowood 24 21 5 33 8 23

Totals for planted species 405 17 69 23 94 382

Totals for non-planted species 349 7 23 0 0 329

Totals for all species 754 12 92 12 94 711

1

Plants that have no foliage, discolored foliage, or malformed fruiting structures.

2

Plants damaged from feeding by deer or other herbivores.

3

Total area of 1.06 acres was planted.

4

Species was planted.
Summary 29

Summary

Maintenance and improvement of transportation infrastructure commonly necessitates alteration of existing stream 

channels and (or) naturally occurring wetlands. Compensatory 

mitigation for wetland and stream encroachments is usually 

required by Federal and State regulatory agencies and commonly includes modification or construction of wetlands, 

stream channels, and associated riparian buffers. From 1998 

through 2003, the Pennsylvania Department of Transportation 

(PennDOT) made roadway improvements to 5.5 mi of U.S. 

Highway 202 in Chester and Montgomery Counties, Pa. To 

compensate for authorized disturbance of naturally occurring wetlands and streams, PennDOT constructed 0.42 acre 

of emergent wetland and 0.94 acre of scrub-shrub/forested 

wetland and modified sections of a 1,600-foot reach of Valley 

Creek with woody riparian plantings and streambank-stabilization structures (including rock deflectors). The constructed 

wetland is in the headwaters of an unnamed tributary to Valley 

Creek and is about 1 straight-line mile south of the modified 

stream reach, which is within Valley Forge National Historical 

Park (Valley Forge Park). In accordance with project permits 

and additional guidance issued by the U.S. Army Corps of 

Engineers to PennDOT and Tredyffrin Township, the U.S. 

Geological Survey (USGS), in cooperation with PennDOT, 

collected data from 2000 through 2006 to quantify changes 

in 1) the vegetation, soils, and extent of emergent and scrubshrub/forested parts of the constructed wetland, 2) the profile, dimension, and substrate in the vicinity of stabilization 

structures placed at two locations within the modified stream 

reach, and 3) the woody vegetation within the planted riparian 

buffer. The data for this investigation were collected using an 

approach adapted from previous investigations so that findings 

may be more easily transferred among projects with similar 

objectives.

Areal cover by planted and non-planted vegetation growing within the emergent and scrub-shrub/forested parts of 

the constructed wetland exceeded 85 percent throughout this 

investigation, a criterion set forth in special condition 25c in 

the U.S. Army Corps of Engineers project permit. Areal cover 

in the emergent part of the constructed wetland ranged from 

101 to 139 percent (fall 2001 and fall 2000, respectively) and 

was 135 percent in fall 2006, the final year of data collection. 

Frequent and long-lasting soil saturation favored obligatewetland species like Typha latifolia (broadleaf cattail) and 

Scirpus validus (great bulrush), which maintained dominance 

in the emergent wetland throughout the study. Sc. validus was 

the only planted herbaceous species that provided appreciable 

cover because it was best suited to effectively compete with 

Ty. latifolia. Although Sc. validus initially covered the greatest area within the emergent wetland (43 percent in fall 2000), 

Ty. latifolia steadily increased throughout the study (from 

30 percent in 2000 to 78 percent in 2006) and eventually 

displaced Sc. validus, which contributed only 20 percent cover 

in 2005 and 2006. Other species such as Impatiens capensis

(jewelweed) and Agrostis stolonifera (spreading bentgrass) 

were sparingly present throughout the study.

Areal cover in the scrub-shrub/forested part of the 

constructed wetland ranged from 97 percent in 2001 to 

146 percent in 2000 and was 139 percent in 2006. Echinocloa 

crusgalli (barnyard grass), an annual invasive from Eurasia, 

initially established the newly disturbed soils in 2000 (areal 

cover was 56 percent), but by 2002, E. crusgalli was not growing in any of the sample plots, and other species including 

Ag. stolonifera, Festuca rubra (red fescue), Cornus spp. (dogwood species), and Sal. nigra were becoming more common. 

Sal. nigra contributed 30 percent cover by fall 2003. Rapid 

colonization of this species resulted in annual increases in 

cover through 2006 when 15 to 25 ft tall Sal. nigra trees dominated the tree/shrub stratum (48 percent of the areal cover). 

The next most common woody plant in 2006 was Cornus spp., 

which contributed 13-percent cover. Ag. stolonifera and 

Ty. latifolia (21- and 17-percent areal cover, respectively) 

were dominant herbaceous components of the mostly shaded 

understory. Ag. stolonifera favored the well-shaded areas, and 

Ty. latifolia grew near the margins of the scrub-shrub/forested 

wetland where somewhat more sunlight was available. Other 

notable herbaceous species that were observed at the end of 

monitoring in 2006 included Polygonum persicaria (lady’s 

thumb; 11-percent areal cover), Sc. cyperinus (wool grass; 

7-percent areal cover), and Urtica dioica (stinging nettle; 

5-percent areal cover).

Longitudinal profiles surveyed near rock deflectors in 

two short (100-ft) reaches within the modified stream reach 

maintained a constant slope throughout the monitoring period, 

most likely because of the presence of bedrock control. The 

two surveyed reaches are within the modified stream reach 

and are separated by a distance of about 300 ft. The cross-section geometry in the upstream reach was virtually unchanged 

during the monitoring period. The cross-section geometry 

in the downstream reach experienced little change during 

the first 3 years of monitoring. During the 2005 assessment, 

notable channel erosion was measured, and the 2006 assessment documented substantially more, totaling a 23-percent 

increase in cross-sectional area when compared to the initial 

assessment. Streambank erosion resulted in over 10 ft of 

bank migration over the monitoring period, leaving the rock 

deflectors mid-stream where they provide no protection of the 

bank. As indicated by the change in channel morphology at the 

downstream reach it is apparent that the rock deflectors were 

ineffective at adequately protecting the bank from erosion. 

Particle distributions in both reaches, in general, became more 

fine over most of the monitoring period with the exception of 

the 2006 assessment, which showed coarsening in the 15thand 50th-percentile size categories at the upstream reach. There 

was no evidence of deposition associated with the coarsening 

of the upstream reach in 2006, indicating transport capability 

was maintained or increased. The trend toward a finer particle 

distribution in the downstream reach suggests a decrease in 

sediment transport commonly associated with channel widening.
30 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

In the riparian buffer adjacent to the modified stream 

reach, the most reliable time frame for interpretation of 

trends in the number and well being of riparian plantings 

is 2003–2006. The most prevalent tree species in 2003 was 

Platanus occidentalis (63 individuals), followed by Carpinus 

caroliniana (ironwood; 35 plants), Quercus palustris (pin 

oak; 33), Alnus serrulata (smooth alder; 30), Acer rubrum

(red maple; 26), Acer saccharinum (silver maple; 17), and 

Sal. nigra (10). The most prevalent shrubs in 2003 were 

Cornus spp. (dogwood species; 98 individuals), followed by 

Salix discolor (pussy willow; 51), Physocarpus opulifolius

(ninebark) and Viburnum dentatum (arrowood) (28 plants 

each), Clethra alnifolia (summersweet; 27), and Spirea virginiana (Virginia spirea; 4). A large percentage of trees and 

shrubs were stressed in 2003 after surviving two previous 

years of extensive drought. The most-stressed species in 2003 

included Q. palustris (65 percent), Al. serrulata (36 percent), 

Ac. rubrum (34 percent), and Sa. discolor (57 percent). Trees 

and shrubs that appreciably declined in number between 2003 

and 2006 (including Sal. nigra, Al. serrulata, Ag. saccharinum, Sa. discolor, and Cl. alnifolia) generally exhibited more 

stress in 2003 compared to their counterparts that remained 

nearly constant or increased in number throughout the study.

In the year preceding the fall 2006 monitoring, infrequent but debris-laden overbank flows breached some of the 

exclosure fences, allowing deer and other herbivores uninhibited access. Browsing that ensued was most common among 

the planted shrub species; greater than 25 percent of Cornus 

spp., Cl. alnifolia, V. dentatum, and Sa. discolor plants were 

browsed. Dissimilarities in the incidence of browsing and 

stress among these species contributed to a decrease in the 

number of planted trees and shrubs and an increase in the 

number of non-planted plants between 2001 and 2006. Despite 

replacement of dead individuals in 2001 and 2002, planted 

trees decreased from 214 in 2001 to 171 in 2006 and shrubs 

decreased from 546 in 2001 to 225 in 2006. By contrast, the 

two most prevalent non-planted native species [Acer negundo

(box elder) and Gymnocladus dioicus (Kentucky coffee tree)] 

more than doubled in number over the same time period (from 

110 to 244). The density of planted and non-planted trees and 

shrubs was 711 plants per acre. Determination of compliance 

with permit condition 29, which establishes density requirements for planted and appropriate non-planted species within 

the riparian buffer, will be evaluated by the U.S. Army Corps 

of Engineers.

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and vegetative characteristics of a relocated stream reach, 

constructed wetland, and riparian buffer, Upper Saucon 

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Geological Survey Scientific Investigations Report 2006–

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data, Pennsylvania, water year 2002, volume 1, Delaware 

River Basin: U.S. Geological Survey Water-Data Report 

PA-02-1, 527p.

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for Pennsylvania, water year 2003, volume 1, Delaware 

River Basin: U.S. Geological Survey Water-Data Report 

PA-03-1, 637 p.

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for Pennsylvania, water year 2004, volume 1, Delaware 

River Basin: U.S. Geological Survey Water-Data Report 

PA-04-1, 651 p.

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resources data for Pennsylvania, water year 2005, volume 1, 

Delaware River Basin: U.S. Geological Survey WaterData Report PA-05-1, 575 p.

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Maupin, M.A., and Gurtz, M.E., 1998, Revised methods for 

characterizing stream habitat in the National Water-Quality 

Assessment Program: U.S. Geological Survey WaterResources Investigation Report 98–4052, 67 p.

Gordon, N.D., McMahon, T.A., and Finlayson, B.L., 1992, 

Stream hydrology, and introduction for ecologist: Chichester, England, John Wiley and Sons, 526 p.

Kunkle, M.W., 1963, Soil Survey of Chester and Delaware 

Counties, PA: U.S. Department of Agriculture, Soil Conservation Service, 124 p.

Munsell Color, 2000, Munsell Soil Color Charts: New Windsor, N.Y., Gretag Macbeth, variously paged.

Natural Resources Conservation Service, 2008, Web 

soil survey [online]: Soil map for Chester County, 

Pennsylvania (PA029), accessed March 5, 2008, at 

http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx

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System: Cornell University, accessed January 11, 2007, at 

http://climod.nrcc.cornell.edu/.
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2007, at http://www.nrcc.cornell.edu/drought/

PA_drought_periods.html

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riparian forest buffers, revised in 1998, U.S. Department of 

Agriculture report NA-TP-0297, variously paged.

Pennsylvania Department of Conservation and Natural 

Resources, 2000, Limestone and dolomite distribution in 

Pennsylvania (4th ed.) [online]: Bureau of Topographic 

and Geologic Survey, map 15, accessed March 5, 2008, at 

http://www.dcnr.state.pa.us/topogeo/maps/map15.pdf

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data: ESRI International User Conference 2003 Proceedings, accessed January 23, 2008, at http://gis.esri.com/

library/userconf/proc03/ p0904.pdf

Reed, P.B., Jr., 1988, National list of plant species that occur in 

wetlands –northeast region 1 (amended 1993): Fort Collins, Colo., U.S. Fish and Wildlife Service, National Ecology Research Center. Biological Report 88 (26.1), 113 p.

Rhoads, A.F., and Block, T.A., 2000, The plants of Pennsylvania: Philadelphia, Pa., University of Pennsylvania Press, 

1061 p.

Rosgen, D., 1996, Applied river morphology: Minneapolis, 

Minn., Printed Media Companies, 352 p.

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Pennsylvania (4th ed.) [online]: Bureau of Topographic 

and Geologic Survey map 13, accessed March 5, 2008, at 

http://www.dcnr.state.pa.us/topogeo/maps/map13.pdf

Tiner, R.W., 1999, Wetland indicators—A guide to wetland identification, delineation, classification, and mapping: Boca Raton, Fla., Lewis Publishers, 392 p.

URS Greiner Woodward Clyde, 1999a, Valley Creek stream 

enhancement plan for Valley Forge National Historical 

Park, Valley Forge, Pa: King of Prussia, Pa., 10 p.

URS Greiner Woodward Clyde, 1999b, Details and plant 

schedules wilson tract wetland mitigation plan for route 

202, section 400 roadway improvements: King of Prussia, 

Pa., 5 p.

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Engineers Waterways Experiment Station, Technical 

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21, 2005, at http://www.saj.usace.army.mil/permit/

documents/87manual.pdf

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adr06/pdfs/01473169.2006.pdf

Wolman, M.G., 1954, A method of sampling coarse riverbed material: Transactions of the American Geophysical 

Union, v. 35, p. 951–956.

Appendix 1. Photographs of the Constructed Wetland, Tredyffrin Township, 

Chester County, Pennsylvania

Appendix 1 33
34 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 1–1. Photo stations and sampling plots at the constructed wetland, Tredyffrin Township, Chester County, Pennsylvania.

Wetland-compensation siteEnhanced natural wetlandEmergent part of constructed wetlandScrub-shrub/forested part of constructed wetland

BaselineTransect

Sampling plot and number within the constructed wetlandSampling plot and number outside the constructed wetlandPhoto-documentation stationCulvert

PENNSYLVANIA

MONTGOMERYCOUNTY

PHILADELPHIA

CHESTERCOUNTY

TREDYFFRINTOWNSHIP

VALLEY FORGE NATIONAL HISTORICAL PARK 

PHILADELPHIA INTERNATIONAL AIRPORT

WETLAND-COMPENSATION SITE

0 100 FEET

Unnamed

Tributary
Appendix 1 35

Figure 1–2. Annual views of the constructed wetland 

looking northeast to southwest from photo station 1, 

Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 1–1 for location and orientation of photo 

station.)

Oct. 2000

Sept. 2001

Sept. 2002

Sept. 2003

Sept. 2004

Sept. 2005

Sept. 2006
36 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 1–3. Annual views of the constructed wetland 

looking south to north from photo station 2, Tredyffrin 

Township, Chester County, Pennsylvania.

(See figure 1–1 for location and orientation of photo 

station.)

Oct. 2000

Sept. 2001

Sept. 2002

Sept. 2003

Sept. 2004

Sept. 2005

Sept. 2006
Appendix 1 37

Figure 1–4. Annual views of the constructed wetland 

looking southeast to northwest from photo station 3, 

Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 1–1 for location and orientation of photo 

station.)

Oct. 2000

Sept. 2001

Sept. 2002

Sept. 2003

Sept. 2004

Sept. 2005

Sept. 2006
38 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 1–5. Annual views of the constructed wetland 

looking southwest to northeast from photo station 4, 

Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 1–1 for location and orientation of photo 

station.)

Oct. 2000

Sept. 2001

Sept. 2002

Sept. 2003

Sept. 2006

Sept. 2005

Sept. 2004
Appendix 1 39

Figure 1–6. Annual views of the constructed wetland 

looking northwest to southeast from photo station 5, 

Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 1–1 for location and orientation of photo 

station.)

Oct. 2000

Sept. 2001

Sept. 2002

Sept. 2003

Sept. 2006

Sept. 2005

Sept. 2004
40 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 1–7. Annual views of the constructed wetland 

looking northwest to southeast from photo station 6, 

Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 1–1 for location and orientation of photo 

station.)

Oct. 2000

Sept. 2001

Sept. 2002

Sept. 2003

Sept. 2006

Sept. 2005

Sept. 2004
Appendix 2. Water Levels in Plots Outside of the Constructed Wetland

Appendix 2 41
42 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 2–1. Monitoring grid used to sample vegetation at the wetland compensation site, Tredyffrin Township, Chester County, Pennsylvania. 

Wetland-compensation siteEnhanced natural wetlandEmergent part of constructed wetlandScrub-shrub/forested part of constructed wetland

BaselineTransect

Sampling plot and number within the constructed wetlandSampling plot and number outside the constructed wetlandPhoto-documentation stationCulvert

PENNSYLVANIA

MONTGOMERYCOUNTY

PHILADELPHIA

CHESTERCOUNTY

TREDYFFRINTOWNSHIP

VALLEY FORGE NATIONAL HISTORICAL PARK 

PHILADELPHIA INTERNATIONAL AIRPORT

WETLAND-COMPENSATION SITE

0 100 FEET

Unnamed

Tributary
Appendix 2 43

Figure 2–2. Water levels within sampling plots outside of the constructed wetland, Tredyffrin Township, Chester County, Pennsylvania, 

2000-2006. 

plot 0101 plot 0102

plot 0104 plot 0201

plot 0203 plot 0501

plot 0503

GROUND SURFACE

DEPTH TO WATER BELOW GROUND SURFACE

INDICATES WATER LEVEL IS DEEPER BELOW GROUND

EXPLANATION

DEPTH OF, OR DEPTH TO, WATER WITH RESPECT TO GROUND SURFACE, IN INCHES

Appendix 3. Plant Species Growing in Plots Outside of the Constructed Wetland

Table 3–1. Species richness and areal cover of vegetation growing in sampling plots outside of the constructed wetland, Tredyffrin 

Township, Chester County, Pennsylvania, 2000-2006.—Continued

[—, not observed; FACW, facultative-wetland species; FAC, facultative species; FACU, facultative-upland species; NI, no regional indicator status assigned, 

+, indicates a frequency of occurrence in the upper end of the probability range for that category; -, indicates a frequency of occurrence in the lower end of the 

probability range for that category; sp., species]

Species Indicator Areal cover, in percent

Latin name Common name 2000 2001 2002 2003 2004 2005 2006

Acer rubrum red maple FACW+ 1 1 1 — — — —

Agrostis alba redtop FACW — 11 — — 1 — —

Agrostis stolonifera spreading bentgrass FACW — — — 14 11 17 19

Ailanthus altissima tree-of-heaven NI — — 1 3 4 2 1

Ambrosia artemisifolia common ragweed FACU 2 2 — — — — —

Apocynum cannabinum hemp-dogbane FACU — — — 1 1 1 1

Aster novae-angliae New England aster FACW- — — — — — — 1

Aster racemosus small white aster FACW — 3 1 — — — —

Bidens frondosa leafy beggar-ticks FACW 1 — — — — — —

Celastrus orbiculata Oriental Bitter-Sweet UPL — 1 1 — — — —

Celastrus scandens Climbing Bittersweet FACU- 2 — — — 1 4 6

Chenopodium album Lambsquarter FACU+ — 1 — — — — —

Cirsium discolor Field Thistle NI — 1 1 — 11 4 —

Coronilla varia Crown Vetch NI — 1 15 16 — — —

Cornus amomum Silky Dogwood FACW 3 1 1 — — — —

Cornus racemosa (foemina) Gray Dogwood FAC — — 1 10 4 2 1

Cyperus strigosus Sedge Grass FACW 1 — — — — — —

Daucus carota Queen Ann’s Lace NI 1 — — — — — —

Dipsacus sylvestris Teasel NI — 2 2 3 3 1 —

Echinochloa crusgalli Barnyard Grass FACU 5 4 1 — 0 — —

Elaeagnus umbellata Autumn-Olive NI 1 1 4 9 15 21 22

Eleocharis sp. Spikerush Species NI — — — — 1 — —

Eupatorium perfoliatum Common Boneset FACW+ 1 1 1 2 2 2 2

Eupatorium rugosum White Snakeroot FACU- — — — 1 1 — —

Festuca rubra Red Fescue FACU — — 3 4 9 — 3

Impatiens capensis Jewelweed FACW — — — 1 1 — —

Juglans nigra Black Walnut FACU — 6 1 1 3 4 1

Juncus tenuis Yard Rush FAC- 1 — — — — 1 1

Lobelia cardinalis Cardinal Flower FACW+ 2 1 1 1 1 1 1

Lolium perenne Perennial Rye FACU- 26 4 — — — — —

Lonicera japonica Japanese Honeysuckle FAC- — 1 — — 1 — 1

Lonicera sp. Honeysuckle NI — — — — 4 4 1

Lotus Corniculatus Birdsfoot Trefoil FACU- 23 20 11 — 1 — —

Lycopus uniflorus Northern Bunglewed OBL — — — 1 — — —

Lysimachia nummularia Moneywort OBL — — — — — — 0

Appendix 3 45
46 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Table 3–1. Species richness and areal cover of vegetation growing in sampling plots outside of the constructed wetland, Tredyffrin 

Township, Chester County, Pennsylvania, 2000-2006.—Continued

[—, not observed; FACW, facultative-wetland species; FAC, facultative species; FACU, facultative-upland species; NI, no regional indicator status assigned, 

+, indicates a frequency of occurrence in the upper end of the probability range for that category; -, indicates a frequency of occurrence in the lower end of the 

probability range for that category; sp., species]

Species Indicator Areal cover, in percent

Latin name Common name 2000 2001 2002 2003 2004 2005 2006

Melilotus sp. Sweet Clover NI — 2 — — — — —

Morus rubra Red Mulberry FACU 6 6 6 7 7 7 7

Nasturtium officinale Watercress OBL 1 — — — — — —

Oenothera biennis Common Evening Primrose FACU- — — 2 — 1 — —

Panicum dichotomiflorum Witch Grass FACW- 1 — — — — — —

Panicum rigidulum (stipitatum) Red-Top Panic Grass FACW+ — 1 15 1 — — —

Pastinaca sativa Parsnip NI — — — 2 — — —

Phytolacca americana Pokeweed FACU+ 3 1 2 1 — — —

Plantago major Great Plantain FACU 1 — — — — — —

Platanus occidentalis Sycamore FACW- — — 1 3 5 4 4

Polygonum persicaria Lady’s Thumb FACW 2 — — 1 0 — —

Quercus bicolor Swamp Oak FACW+ 1 1 2 4 1 1 2

Quercus palustris Pin Oak FACW — — 1 — — — —

Rosa Multiflora Multiflora Rose FACU 1 — — 2 2 1 3

Rubus hispidus Bristly Blackberry FACW — — — 4 2 1 1

Rubus occidentalis Black Raspberry NI 4 3 2 1 1 4 1

Salix nigra Black Willow FACW+ 6 6 4 4 3 3 4

Scirpus cyperinus Woolgrass FACW+ — — — — 1 — —

Setaria faberi Foxtail UPL 2 1 — — — — —

Solidago canadensis Canada Goldenrod FACU 9 7 11 22 11 12 17

Thaspium trifoliatum Woodland Meadow Parsnip NI — — — — — 2 2

Trifolium pratense Red Clover FACU- — — — 1 — — —

Trifolium repens White Clover FACU- — 6 — — 2 — —

Triodia flava Purpletop NI — — — — 8 6 5

Typha latifolia Broadleaf Cattail OBL 1 1 1 3 6 6 4

Ulmus rubra Red Elm FAC — — — — — 1 1

Viburnum dentatum Arrowwood FAC 1 — 1 — 0 — —

Vitis spp. Grape NI 2 4 1 9 9 10 3

Cumulative Areal Cover 111 101 95 132 134 122 113
Appendix 4. Photographs of Surveyed Cross Sections and Rock Deflectors in 

Valley Creek, Tredyffren Township, Chester County, Pennsylvania

Appendix 4 47
48 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

0 100 FEET 0 100 FEET

0 100 FEET

Group of planted trees and shrubsand identification number

Foot Bridge

Valley Forge Farm

Covered Bridge

PENNSYLVANIA

MONTGOMERY COUNTY

PHILADELPHIA

CHESTER COUNTY

TREDYFFRIN TOWNSHIP VALLEY FORGE NATIONAL HISTORICAL PARK

Stream Reaches and Riparian Buffer

Figure 4–1. Reach of Valley Creek modified with rock deflectors and riparian plantings, Tredyffrin Township, Chester County, Pennsylvania. 
Appendix 4 49

Figure 4–2. Views of the upstream rock deflector and cross section during the initial survey in June 2001 and last survey in September 

2006. 

ROCK DEFLECTOR, JUNE 2001 ROCK DEFLECTOR, SEPTEMBER 2006

LOOKING UPSTREAM, JUNE 2001 LOOKING UPSTREAM, SEPTEMBER 2006

LOOKING FROM LEFT TO RIGHT BANK, JUNE 2001 LOOKING FROM LEFT TO RIGHT BANK, SEPTEMBER 2006
50 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Figure 4–2. Views of the upstream rock deflector and cross section during the initial survey in June 2001 and last survey in September 

2006.—Continued

LOOKING FROM RIGHT TO LEFT BANK, JUNE 2001 LOOKING FROM RIGHT TO LEFT BANK, SEPTEMBER 2006

LOOKING DOWNSTREAM, JUNE 2001 LOOKING DOWNSTREAM, SEPTEMBER 2006
Appendix 4 51

Figure 4–3. Views of the downstream rock deflector and cross section during the initial survey in June 2001 and last survey in 

September 2006.

ROCK DEFLECTOR, JUNE 2001

LOOKING UPSTREAM, JUNE 2001

LOOKING FROM LEFT TO RIGHT BANK, JUNE 2001

ROCK DEFLECTOR, SEPTEMBER 2006

LOOKING UPSTREAM, SEPTEMBER 2006

LOOKING FROM LEFT TO RIGHT BANK, SEPTEMBER 2006
52 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach

Figure 4–3. Views of the downstream rock deflector and cross section during the initial survey in June 2001 and last survey in 

September 2006.—Continued

LOOKING FROM RIGHT TO LEFT BANK, JUNE 2001 LOOKING FROM RIGHT TO LEFT BANK, SEPTEMBER 2006

LOOKING DOWNSTREAM, JUNE 2001 LOOKING DOWNSTREAM, SEPTEMBER 2006
Appendix 5. Photographs of Selected Tree and Shrub Plantings in the Riparian 

Buffer, Tredyffrin Township, Chester County, Pennsylvania

Appendix 5 53
54 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

0 100 FEET 0 100 FEET

0 100 FEET

Group of planted trees and shrubsand identification number

Foot Bridge

Valley Forge Farm

Covered Bridge

PENNSYLVANIA

MONTGOMERY COUNTY

PHILADELPHIA

CHESTER COUNTY

TREDYFFRIN TOWNSHIP VALLEY FORGE NATIONAL HISTORICAL PARK

Stream Reaches and Riparian Buffer

Figure 5–1. Locations of tree and shrub plantings in the riparian buffer along Valley Creek, Tredyffrin Township, Chester County, Pennsylvania. 
Appendix 5 55

Figure 5–2. Annual views of riparian-buffer plantings in group 1, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2002 Sept. 2005

Sept. 2003 Sept. 2006

Sept. 2004
56 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 5–3. Annual views of riparian-buffer plantings in group 4, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2004

Sept. 2002

Sept. 2003 Sept. 2006

Sept. 2005
Appendix 5 57

Figure 5–4. Annual views of riparian-buffer plantings in group 10, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2004

Sept. 2003 Sept. 2006

Sept. 2002 Sept. 2005
58 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 5–5. Annual views of riparian-buffer plantings in group 11, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2004

Sept. 2003 Sept. 2006

Sept. 2002 Sept. 2005
Appendix 5 59

Figure 5–6. Annual views of riparian-buffer plantings in group 13, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2002 Sept. 2005

Sept. 2004

Sept. 2003 Sept. 2006
60 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 5–7. Annual views of riparian-buffer plantings in group 15, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2004

Sept. 2003 Sept. 2006

Sept. 2002 Sept. 2005
Appendix 5 61

Figure 5–8. Annual views of riparian-buffer plantings in group 17, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2004

Sept. 2003 Sept. 2006

Sept. 2002 Sept. 2005
62 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 5–9. Annual views of riparian-buffer plantings in group 18, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2004

Sept. 2003 Sept. 2006

Sept. 2002 Sept. 2005
Appendix 5 63

Figure 5–10. Annual views of riparian-buffer plantings in group 24, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2002 Sept. 2005

Sept. 2003 Sept. 2006

Sept. 2004
64 Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach 

Figure 5–11. Annual views of riparian-buffer plantings in group 34, Tredyffrin Township, Chester County, Pennsylvania. 

(See figure 5–1 for location.)

Sept. 2002 Sept. 2005

Sept. 2003 Sept. 2006

Sept. 2004

Chaplin—Physical and Vegetative Characteristics of a Newly Constructed Wetland and Modified Stream Reach—Scientific Investigations Report 2009-5020