U.S. Department of the Interior

U.S. Geological Survey

REGIONAL CURVE DEVELOPMENT AND

SELECTION OF A REFERENCE REACH IN THE

NON-URBAN, LOWLAND SECTIONS OF THE

PIEDMONT PHYSIOGRAPHIC PROVINCE,

PENNSYLVANIA AND MARYLAND

by Kirk E. White

Water-Resources Investigations Report 01-4146

In cooperation with the

PENNSYLVANIA DEPARTMENT OF ENVIRONMENTAL PROTECTION

New Cumberland, Pennsylvania

2001
ii

U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information Copies of this report may be

write to: purchased from:

District Chief U.S. Geological Survey

U.S. Geological Survey, WRD Branch of Information Services

215 Limekiln Road Box 25286

New Cumberland, Pennsylvania 17070-2424 Denver, Colorado 80225-0286

Email: dc_pa@usgs.gov Telephone: 1-888-ASK-USGS
iii

CONTENTS

Page

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

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

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Purpose and scope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Description of study area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Study design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

Regional-curve development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Description of streamflow-measurement stations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Evaluation of the regional curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Reference-reach selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

Comparison of estimates from lowland regional curves and Dunne and Leopold regional

curves for reference-reach characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Limitations of the investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Summary and conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

Selected references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

ILLUSTRATIONS

Figure 1. Map showing locations of the Lowland Sections of the Piedmont

Physiographic Province, project site, reference reach, and streamflowmeasurement stations selected for regional-curve development,

Pennsylvania and Maryland . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2-7. Photographs showing:

2. View looking upstream at stream reach containing the surveyed cross

section for Manatawny Creek near Pottstown, Pennsylvania. . . . . . . . . 6

3. View looking downstream at stream reach containing both surveyed

cross sections for French Creek near Phoenixville, Pennsylvania. . . . . 7

4. View looking downstream at stream reach containing one of the two

surveyed cross sections for Perkiomen Creek at East Greenville,

Pennsylvania. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

5. View looking upstream at stream reach containing both surveyed cross

sections at West Branch Perkiomen Creek at Hillegas,

Pennsylvania. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

6. View looking downstream at stream reach containing both surveyed

cross sections at Sucker Run near Coatesville, Pennsylvania. . . . . . . . 10

7. View looking upstream at stream reach containing the surveyed cross

section for Big Pipe Creek at Bruceville, Maryland. . . . . . . . . . . . . . . . 11
iv

ILLUSTRATIONS—Continued

Page

Figures 8-11. Graphs showing:

8. Regional curve representing relation between bankfull cross-sectional

area and drainage area in non-urban, Lowland Sections of the

Piedmont Physiographic Province, Pennsylvania and Maryland.. . . . 12

9. Regional curve representing relation between bankfull cross-sectional

mean depth and drainage area in non-urban, Lowland Sections of

the Piedmont Physiographic Province, Pennsylvania and

Maryland. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

10. Regional curve representing relation between bankfull cross-sectional

width and drainage area in non-urban, Lowland Sections of the

Piedmont Physiographic Province, Pennsylvania and Maryland.. . . . 13

11. Regional curve representing relation between bankfull discharge and

drainage area in non-urban, Lowland Sections of the Piedmont

Physiographic Province, Pennsylvania and Maryland. . . . . . . . . . . . . 14

12. Map showing location of project site and reference reach on Bermudian Creek,

Adams County, Pennsylvania . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

13. Photograph showing view looking downstream at cross section 526 of the

reference reach on Bermudian Creek, Adams County, Pennsylvania . . . . . . 15

TABLES

Table 1. Data collected during assessment of streamflow-measurement stations used

for regional curves in the Lowland Sections of the Piedmont

Physiographic Province, Pennsylvania and Maryland . . . . . . . . . . . . . . . . . . . . . 5

2. Cross-section data collected from assessment of reference reach on

Bermudian Creek, Adams County, Pennsylvania. . . . . . . . . . . . . . . . . . . . . . . . . 17

3. Longitudinal-profile data collected from assessment of reference reach on

Bermudian Creek, Adams County, Pennsylvania. . . . . . . . . . . . . . . . . . . . . . . . . 18
v

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATIONS

Multiply By To obtain

Length

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

Area

square foot (ft2) 0.09290 square meter

square mile (mi2) 2.590 square kilometer

Flow

cubic foot per second (ft3/s) 0.02832 cubic meter per second

Vertical datum: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929—a

geodetic datum derived from a general adjustment of the first-order level nets of the United States and

Canada, formerly called Sea Level Datum of 1929.
vi

GLOSSARY

The terms in this glossary were compiled from numerous sources. Some definitions have been

modified for use within this report.

Bankfull channel—The active stream channel during the bankfull discharge.

Bankfull cross-sectional area—The cross-sectional area of the bankfull channel measured

perpendicular to the streamflow.

Bankfull discharge—The most effective streamflow for moving sediment, forming or removing bars,

forming or changing bends and meanders, and generally doing work that results in the

average morphological characteristics of channels (Dunne and Leopold, 1978).

Bankfull mean depth—The mean depth of the bankfull channel measured perpendicular to the

streamflow.

Bankfull stage—The elevation of the water surface during bankfull discharge.

Bankfull width—The width of the bankfull channel measured perpendicular to the streamflow.

Belt width—Lateral extent of two sequential meanders measured perpendicular to the valley slope.

D##—The numerical value (##) is the percentage of measured particles within a cross section having

an intermediate axis measuring less than a provided dimension.

Drainage area—That area, measured in a horizontal plane, enclosed by a topographic divide from

which direct surface runoff from precipitation normally drains by gravity into the stream

above the specified point.

Gage height—Water-surface elevation referred to some arbitrary station datum. Gage height

commonly is used interchangeably with the more general term “stage.”

Reference reach—A reach of stream displaying characteristics of a stable stream channel that is used

as a template for design of a stream-restoration project.

Regional curve—A regression of the relations among drainage area, selected cross-sectional

parameters, and streamflow.

Regulation—A condition where streamflow is controlled by an upstream man-made feature.

Stream reach—A section of stream extending between 10 and 20 bankfull widths in length.

Stream restoration—For this report, adjusting stream dimensions, pattern, and profile to a condition

where it effectively accommodates a range of streamflow and sediment and supports diverse

habitat.

Watershed—For this report, used interchangeably with drainage area.
1

ABSTRACT

Stream-restoration projects utilizing naturalstream designs frequently are based on the bankfull-channel characteristics of a stream reach that is

accommodating streamflow and sediment transport without excessive erosion or deposition. The

bankfull channel is identified by the use of field

indicators and confirmed with tools such as

regional curves. Channel dimensions were surveyed at six streamflow-measurement stations

operated by the U.S. Geological Survey in the

Gettysburg-Newark Lowlands Section and Piedmont Lowlands Section of the Piedmont Physiographic Province in Pennsylvania and Maryland.

Regional curves were developed from regression

analyses of the relation between drainage area and

cross-sectional area, mean depth, width, and

streamflow of the bankfull channel. Regional

curves were used to confirm the identification of

the bankfull channel at a reference reach. Stream

dimensions and characteristics of the reference

reach were measured for extrapolation into the

design of a steam-restoration project on Bermudian

Creek in Adams County, Pa.

Dimensions for cross-sectional area, mean

depth, width, and computed streamflow of the

bankfull channel in all surveyed riffle cross sections in the reference reach were within the

95-percent confidence interval bounding the

regression line representing bankfull channel

geometry in the Lowland Sections of the Piedmont

Physiographic Province. The average bankfull

cross-sectional area, bankfull mean depth, and

computed bankfull discharge for riffle cross sections in the reference reach ranged from 15.4 to

16.5 percent less than estimates determined from

the lowland regional curves. Average bankfull

channel width was about 2 percent greater than

estimates. Cross-sectional area, mean depth, and

computed streamflow corresponding to the bankfull stage at the reference reach were 31.4, 44.4, and

9.6 percent less, respectively, than estimates

derived from the regional curves developed by

Dunne and Leopold in 1978. Average bankfull

channel width at the reference reach was 16.7 percent greater than the Dunne and Leopold estimate.

The concepts of regional curves and reference reaches can be valuable tools to support

efforts in stream restoration. Practitioners of

stream restoration need to recognize them as such

and realize their limitations. The small number of

stations available for analysis is a major limiting

factor in the strength of the results of this investigation. Subjective selection criteria may have

unnecessarily eliminated streamflow-measurement stations that could have been included in the

regional curves. A bankfull discharge with a recurrence interval within the 1- to 2-year range was

used as a criteria for confirmation of the bankfull

stage at each streamflow-measurement station.

Many researchers accept this range for recurrence

interval of the bankfull discharge; however, literature provides contradictory evidence. The use of

channel-characteristics data from a reference reach

without any monitoring data to document the

stability of the reference reach over time is a topic

of debate.

INTRODUCTION

Restoration projects of stream channels with

excessive erosion, deposition, or degraded habitat

are being proposed by Federal, state, local, and private organizations in an effort to return the

impaired streams to more stable and biologically

productive conditions. Traditional engineering

practices for stream stabilization frequently rely on

hardening the sections of a stream impacted by

erosive forces. Recent restoration projects propose

to utilize a natural stream design approach that

emphasizes working in concert with natural

stream processes as opposed to combating them.

Accelerated bank erosion in a section of Bermudian Creek, Adams County, Pa., is endangering

some structures that border the creek and may

impair present habitat. This reach of Bermudian

REGIONAL CURVE DEVELOPMENT AND SELECTION OF A REFERENCE REACH

IN THE NON-URBAN, LOWLAND SECTIONS

OF THE PIEDMONT PHYSIOGRAPHIC PROVINCE, PENNSYLVANIA AND MARYLAND

By Kirk E. White
2

Creek has been identified for streambank stabilization utilizing natural stream design. The restoration project will be designed by the Pennsylvania

Department of Environmental Protection (PaDEP),

Bureau of Waterways Engineering, to accommodate the bankfull discharge1 for this segment of

Bermudian Creek.

The bankfull discharge is considered to be

the most effective streamflow for moving sediment, forming or removing bars, forming or

changing bends and meanders, and generally

doing work that results in the average morphological characteristics of channels (Dunne and

Leopold, 1978). Bankfull discharge occurs 1 or

2 days each year with an average recurrence interval of 1.5 years (Leopold, 1994).

As the basis of the restoration design, the

bankfull channel is defined and verified by field

reconnaissance and direct measurement of channel

features. In addition to identifying the bankfull

channel on the basis of field indicators, an independent source of information that supports the

identification is needed.

Some of the more common tools available

for supporting the selection of the bankfull channel

are regional curves. One set of regional curves

developed by Dunne and Leopold (1978) was

intended to be representative of bankfull-channel

dimensions throughout the eastern United States.

The applicability of one set of regional curves to

the multiple physiographic provinces and/or geology throughout Pennsylvania has not been verified.

Dimensions of the bankfull channel are

defined by characteristics such as cross-sectional

area, width, and mean depth. These characteristics

are highly correlated with drainage area (Dunne

and Leopold, 1978). Regional curves are developed

by regression analysis and provide estimated

bankfull-channel dimensions when drainage area

is known. Estimates of bankfull dimensions are

helpful for confirming field identification of the

bankfull channel.

PaDEP will develop a restoration design on

the basis of stream-channel measurements made at

a stream reach having similar runoff characteristics to those of the proposed restoration site. The

stream reference reach must appear stable, for

example, capable of effectively accommodating

streamflow and sediment without excessive channel erosion or deposition. A comprehensive site

assessment of a reference reach will quantify

numerous bankfull-channel characteristics of an

apparently stable form from which to simulate the

morphology of restored channel.

In 1999, PaDEP proposed a study to develop

regional curves representative of channel geometry in the Piedmont Physiographic Province and to

quantify channel characteristics of a stream reach

for use as a template in a stream-restoration

design. PaDEP and the U.S. Geological Survey

(USGS) conducted this study as a cooperative

effort.

Purpose and Scope

This report describes the methods used, data

collected, the results of regional-curve development, and the selection of a reference reach.

Regional curves developed from channel-characteristics data collected from December 1999 to

March 2000 that represent channel dimensions in

the Piedmont Lowland and Gettysburg-Newark

Lowland Sections of the Piedmont Physiographic

Province within Pennsylvania and Maryland are

presented. Channel characteristics of a reference

reach on Bermudian Creek in the Gettysburg-Newark Lowland Section in Adams County, Pa., also

are presented.

Description of Study Area

The Piedmont Physiographic Province is

separated into three sections: Piedmont Upland

Section, Piedmont Lowland Section, and the Gettysburg-Newark Lowland Section. This investigation is restricted to streamflow-measurement

stations in the two lowland sections. Major locations and their physiographic contexts related to

this investigation are shown in figure 1.

The Piedmont Lowland Section study area in

Pennsylvania consists of broad, moderately dissected valleys separated by broad low hills. The

Section is developed primarily on limestone and

dolomite rock. Karst topography is common. Local

relief in the Section generally is less than 100 ft but

may be as much as 300 ft. Land-surface elevations

in the Section range from 170 to 630 ft. Drainage is

basically dendritic in pattern, but some areas have

virtually no pattern because of the well-developed

subsurface drainage (Sevon, 2000).

1 Words presented in bold type are defined in the

Glossary section of this report.
3

The Gettysburg-Newark Lowland Section

study area in Pennsylvania and Maryland consists

mainly of rolling low hills and valleys developed

on red sedimentary rock. Isolated higher hills

developed on diabase, baked sedimentary rock,

and conglomerates. Almost all the underlying sedimentary rock dips to the north or northwest, and

many smaller drainageways are oriented normal to

the direction of dip so that some topography has a

northeast-southwest linearity. The basic drainage

pattern is dendritic. Relief generally is in the area

of 100 to 200 ft but locally is up to 600 ft on some of

the isolated hills. Elevation in the Section ranges

from 40 to 1,335 ft (Sevon, 2000).

Figure 1. Locations of the Lowland Sections of the Piedmont Physiographic Province, project site, reference

reach, and streamflow-measurement stations selected for regional-curve development, Pennsylvania and

Maryland. (Physiographic Provinces from Sevon, 2000.)
4

STUDY DESIGN

Only streamflow-measurement stations in

the Lowland Sections of the Piedmont Physiographic Province (Sevon, 2000) were included in

developing these regional curves. Streamflowmeasurement stations in the Upland Section of the

Piedmont are omitted from this initial regional

relation because of potentially major differences in

runoff characteristics between the Upland and

Lowland Sections. Subjective filtering criteria utilizing Geographic Information System land-use

(U.S. Geological Survey, 1996) and stream coverages (Pennsylvania Department of Transportation,

1997; Alexander and others, 1999) and additional

station-information criteria were used to identify

streamflow-measurement stations with similar

runoff characteristics. The distribution of watershed size, upstream from the selected stations,

needed to be large enough to provide confidence in

the relation over a range of drainage areas. The filtering criteria used for selecting streamflow-measurement stations are listed below.

• The station is within the boundaries of a

Lowland Section of the Piedmont

Physiographic Province.

• The station has at least 10 years of record.

• The period of record for the station extends

at least to 1985 to minimize the extent to

which changes in land use may have affected

the channel since the station was active.

• No more than 20 percent of the upstream

watershed is classified as urban land use.

• Streamflow at the station is subjected to no

greater than 20 percent regulation.

The filtering criteria were applied to a comprehensive listing of current and historical continuous- and partial-record stations operated by the

USGS in Pennsylvania and Maryland. Stations

meeting all criteria were considered for inclusion

in the investigation. Station descriptions describing flow conditions and site characteristics are on

file in USGS offices, and in some instances, field

reconnaissance was used to finalize the list of stations included in the formulation of the regional

curves. On the basis of the filtering criteria, six

streamflow-measurement stations were selected

for inclusion in the regional-curve development.

Procedures for field assessments, outlined by

Leopold (1994) and Rosgen (1996), were followed

for the data collection at each station. Deviations

from the established procedure, warranted because

of site conditions, are discussed along with the specific details describing each streamflow-measurement station. Surveyed elevations are recorded to

the hundredth of a foot. Stream slopes calculated

from survey data are presented to the thousandth

of a foot to provide the user with relative differences between stream slopes and sufficient data for

rounding purposes.

Field reconnaissance was conducted to

locate a reference reach that could serve as a template for the restoration design. Qualitative criteria

were developed to identify a stream reach that

appeared to effectively accommodate streamflow

and sediment transport without excessive channel

erosion or deposition. The criteria used to identify

the reference reach are as follows.

• Runoff characteristics are similar to those of

the restoration project site.

• Channel width and depth within the reach

do not change dramatically.

• Rapidly eroding banks or areas of excessive

deposition are not evident.

• Riffles are characterized by an appropriate

degree of embeddedness.

• Accumulation of debris is not excessive.

The selection criteria were applied to stream

segments in Bermudian Creek and elsewhere in

the vicinity of the restoration project site. A 1,000-ft

reach of Bermudian Creek upstream from the

project site met the criteria and was selected. Field

procedures for characterizing a reference reach,

outlined by Harrelson and others (1994) and Rosgen (1996), were followed for the assessment of the

reference reach on Bermudian Creek.
5

REGIONAL-CURVE DEVELOPMENT

Because many restoration designs are dependent on bankfull-channel dimensions, correctly

identifying the bankfull stage is essential to a successful design. According to Dunne and Leopold

(1978), the width, mean depth, and cross-sectional

area of the bankfull channel are highly correlated

with the size of the basin (drainage area) in a given

region. Familiarity with these regional relations is

useful for field identification of the bankfull channel. A regional curve is a regression of these relations and provides estimated channel dimensions

and streamflow for the bankfull channel when

drainage area is known.

USGS streamflow-measurement stations

provide a source of readily available and reliable

information from which regional curves can be

developed. The drainage area has been accurately

determined for each station. Streamflow measurements provide a long-term record of channel

dimensions over a broad range of streamflows.

Peak-flow analysis of station record provides the

frequencies of occurrence for a range of streamflows. By identifying the bankfull stage at a

streamflow-measurement station, the investigator

can determine if the associated streamflow is

within the 1- to 2-year recurrence-interval range.

Once confirmed, the bankfull channel is surveyed

at riffle cross sections and the cross-sectional

dimensions are determined. Plotting the bankfullchannel dimensions and streamflow for each

streamflow-measurement station in relation to its

drainage area provides the data necessary for

defining the relation. A “best-fit” regression line is

applied to the data to form the regional curve. Use

of the USGS streamflow-measurement data does

not necessarily provide absolute confirmation of

the bankfull discharge but does support the identification of the bankfull channel when used along

with other field indicators. Once developed, investigators can use regional curves at unmonitored

sites to support or refute their identification of the

bankfull channel within regions having similar

runoff characteristics.

Applying the previously described filtering

criteria to USGS streamflow-measurement stations

identified six stations in the Lowland Sections of

the Piedmont Physiographic Province. Characteristics of each streamflow-measurement station

included in the investigation are discussed below.

Other data directly relating to the site assessments

are included in table 1. Rosgen (1996) stream type

refers to a stream classification based on the morphological characteristics of a stream reach.

Table 1. Data collected during assessment of streamflow-measurement stations used for regional curves in the

Lowland Sections of the Piedmont Physiographic Province, Pennsylvania and Maryland

[WY, water year1; mi2, square miles; ft, feet; ft2, square feet; ft3/s, cubic feet per second; ft/ft, feet per foot;

GNL, Gettysburg-Newark Lowland Section; PL, Piedmont Lowland Section]

U.S.

Geological

Survey

station

identification

number

(see fig. 1)

Period of

record

(WY)

Physiographic

section

Rosgen

stream

type2

Drainage

area

(mi2)

Bankfull

crosssectional

area

(ft2)

Bankfull

width

(ft)

Bankfull

mean

depth

(ft)

Estimated

bankfull

stage

(ft)

Estimated

bankfull

discharge

(ft3/s)

Recurrence

interval

(years)

Slope

(ft/ft)

01471980 1974–2000 GNL C4 85.5 468 90.1 5.19 6.26 2,340 1.3 30.001

01472157 1969–2000 GNL C3 59.1 316 87.1 3.63 7.78 1,440 1.3 .004

01472198 1982–2000 GNL C4 38.0 304 117 2.65 3.83 1,190 1.4 .002

01472199 1982–2000 GNL C4 23.0 202 96.5 1.94 4.79 1,000 1.5 .004

01480610 1964–2000 PL B5c 2.57 24.0 17.8 1.36 4.83 143 1.2 .009

01639500 1948–2000 GNL C4 102 616 101 6.12 7.93 3,060 1.5 .001

1 The 12-month period October 1 through September 30 designated by the calendar year in which it ends.

2 Rosgen, 1996.

3 Slope not computed from entire reach.
6

Description of Streamflow-Measurement

Stations

USGS Station Number: 01471980

Stream Name: Manatawny Creek

Location: near Pottstown, Pennsylvania

(Lat 40°16′22′′, Long 75°40′49′′)

The streamflow-measurement station on

Manatawny Creek monitors streamflow from an

85.5-mi2 watershed, less than 2 percent of which is

classified as urban land use (U.S. Geological Survey, 1996). Streamflow upstream from the station is

not regulated, 26 percent of the watershed is

underlain by carbonate geology, and 56 percent is

covered by forest. Only about 15 percent of the

Manatawny Creek watershed upstream from the

station is in the Gettysburg-Newark Lowland Section of the Piedmont Physiographic Province

(Pennsylvania Department of Transportation, 1997;

Sevon, 2000). The remainder is in the Great Valley

Section of the Ridge and Valley Physiographic

Province (45 percent) and the Reading Prong Section of the New England Physiographic Province

(40 percent). Manatawny Creek near Pottstown is a

continuous streamflow-measurement station about

180 ft upstream from a bridge. The bridge does not

appear to constrict the bankfull discharge. Streamflow-measurement data stored in the USGS hydrologic data base indicate wading measurements at

this station are usually made in the approximate

location of the cross-section survey. High-water

measurements are made from the bridge.

The bankfull channel clearly was defined

throughout most of the reach by field indicators

such as riparian vegetation and depositional features. The cross-section survey was limited to one

cross section conducted in a “run” (an area of intermediate relative velocity) because of the presence

of a divided channel throughout the upstream half

of the reach. Two riffles were eliminated from consideration because of their proximity to the

divided channel. One riffle was within the divided

channel section, and channel geometry was

strongly affected. The other riffle was at the confluence of the two flow paths and was still in transition to a single flow path. The stream reach

containing the surveyed cross section is shown in

figure 2. A pebble count was conducted within the

cross section to determine the distribution of particle sizes on the streambed. The elevation of the

bankfull stage was surveyed to the outside vertical

staff gage from which the gage height and associated bankfull discharge were determined. The

channel geometry at the estimated bankfull discharge, as indicated by streamflow-measurement

data in the USGS database, was used to assist with

confirmation of bankfull selection.

Figure 2. View looking upstream at stream reach containing the surveyed

cross section for Manatawny Creek near Pottstown, Pennsylvania.
7

USGS Station Number: 01472157

Stream Name: French Creek

Location: near Phoenixville, Pennsylvania

(Lat 40°09′05′′, Long 75°36′06′′)

The streamflow-measurement station on

French Creek monitors streamflow from a 59.1-mi2

watershed, less than 1 percent of which is classified

as urban land use (U.S. Geological Survey, 1996).

About 2 percent of the watershed upstream from

the station is regulated, carbonate geology is not

present within the watershed, and 64 percent of

the watershed is covered by forest. About 38 percent of the French Creek watershed upstream from

the station is in the Gettysburg-Newark Lowland

Section of the Piedmont Physiographic Province

(Pennsylvania Department of Transportation, 1997;

Sevon, 2000). The remainder is in the Piedmont

Uplands. French Creek near Phoenixville is a continuous streamflow-measurement station about

70 ft downstream from a bridge. The bridge may

have a slight effect on the bankfull discharge.

Streamflow-measurement data stored in the USGS

hydrologic data base indicate wading measurements usually are made in the vicinity of the station. High-water measurements are made from the

bridge.

The bankfull channel, in the vicinity of the

streamflow-measurement station, was poorly

defined because of excessive bank erosion. Directly

across from the streamflow-measurement shelter is

an auxiliary channel, separated from the main

channel by a berm that extends 500 ft downstream.

This auxiliary channel is a component of the bankfull channel and contains flowing water during

moderate streamflow. Riffles within this area were

not surveyed because of the resulting divided

channel at the bankfull discharge. Excellent bankfull indicators were identified on a point bar beginning about 700 ft downstream from the station.

Two cross sections were surveyed at riffles within

the reach, and pebble counts were conducted

within each to determine the particle distribution.

The stream reach containing both surveyed cross

sections is shown in figure 3. The bankfull widths,

mean depths, and cross-sectional areas of the two

cross sections were averaged to determine the

input for the regional curves. The bankfull elevation was extended upstream to the streamflowmeasurement station, with some difficulty, to

determine the gage height and streamflow associated with the bankfull stage. The channel geometry at the estimated bankfull discharge, as

indicated by streamflow-measurement data in the

USGS data base, was used to assist with confirmation of the bankfull selection.

Figure 3. View looking downstream at stream reach containing both surveyed

cross sections for French Creek near Phoenixville, Pennsylvania.
8

USGS Station Number: 01472198

Stream Name: Perkiomen Creek

Location: at East Greenville, Pennsylvania

(Lat 40°23′38′′, Long 75°30′57′′)

The streamflow-measurement station on

Perkiomen Creek monitors streamflow from a

38.0-mi2 watershed, 2 percent of which has urban

land use (U.S. Geological Survey, 1996). Streamflow upstream from the station is not regulated,

3 percent of the watershed is underlain by carbonate geology, and 54 percent is covered by forest.

About 51 percent of the Perkiomen Creek watershed, upstream from the station, is in the Gettysburg-Newark Lowland Section of the Piedmont

Physiographic Province (Pennsylvania Department of Transportation, 1997; Sevon, 2000). The

remainder is in the Reading Prong Section of the

New England Physiographic Province (40 percent)

and the Great Valley Section of the Ridge and Valley Physiographic Province (9 percent). Perkiomen

Creek at East Greenville is a continuous streamflow-measurement station adjacent to a pool created by a weir immediately downstream from the

shelter. A multi-span bridge is 100 ft downstream

from the weir and does not appear to constrict the

bankfull discharge. Wading streamflow measurements usually are made downstream from the weir

and the bridge. High-water measurements are

made from the bridge.

The bankfull channel in the assessed reach

was fairly well defined. Two cross sections were

surveyed at riffles within the reach, and pebble

counts were conducted within each to determine

the particle distribution. A section of the stream

reach previously was stabilized; however, cross

sections were beyond the affected stream section.

The stream reach containing the upstream surveyed cross section is shown in figure 4. The bankfull widths, mean depths, and cross-sectional areas

of the two cross sections were averaged to determine the input for the regional curves. The bankfull water-surface elevation could not be extended

upstream to the streamflow-measurement station

because of the relatively high-profile weir. The

channel geometry at the estimated bankfull discharge, as indicated by streamflow-measurement

data stored in the USGS data base, was used to

assist with confirmation of the bankfull selection.

Figure 4. View looking downstream at stream reach containing one of the two

surveyed cross sections for Perkiomen Creek at East Greenville, Pennsylvania.
9

USGS Station Number: 01472199

Stream Name: West Branch Perkiomen Creek

Location: at Hillegas, Pennsylvania

(Lat 40°22′26′′, Long 75°31′22′′)

The streamflow-measurement station on the

West Branch of Perkiomen Creek monitors streamflow from a 23.0-mi2 watershed, 2 percent of which

is classified as urban land use (U.S. Geological Survey, 1996). Streamflow is not regulated above the

station, 4 percent of the watershed is underlain by

carbonate geology, and 61 percent is covered by

forest. About 43 percent of the watershed upstream

from the station is in the Gettysburg-Newark Lowland Section of the Piedmont Physiographic Province (Pennsylvania Department of Transportation,

1997; Sevon, 2000). The remainder of the watershed is in the Reading Prong Section of the New

England Physiographic Province (50 percent) and

the Great Valley Section of the Ridge and Valley

Physiographic Province (7 percent). West Branch

Perkiomen Creek at Hillegas is a continuous

streamflow-measurement station adjacent to a pool

created by a weir immediately downstream from

the shelter. The rating is considered to be poorly

defined above 560 ft3/s because of the lack of a

good location from which to make high-water

measurements. Wading streamflow measurements

are conducted throughout the stream reach both

upstream and downstream from the weir.

The assessed reach was separated from the

pool behind the weir by a high-profile rock outcrop. The bankfull channel clearly was defined

throughout most of the assessed reach. Two cross

sections were surveyed at riffles within the

assessed reach, and pebble counts were conducted

within each to determine the particle distribution.

The stream reach containing both surveyed cross

sections is shown in figure 5. The bankfull widths,

mean depths, and cross-sectional areas of the two

cross sections were averaged to determine the

input for the regional curves. Despite the presence

of the rock outcrop, the bankfull elevation could be

extended to the outside vertical staff gage adjacent

to the streamflow-measurement station, with reasonable certainty, to determine the gage height and

streamflow associated with the bankfull stage. The

channel geometry at the estimated bankfull discharge, as indicated by measurement data in the

USGS database, was used to assist with confirmation of the bankfull selection.

Figure 5. View looking upstream at stream reach containing both surveyed

cross sections at West Branch Perkiomen Creek at Hillegas, Pennsylvania.
10

USGS Station Number: 01480610

Stream Name: Sucker Run

Location: near Coatesville, Pennsylvania

(Lat 39°58′20′′, Long 75°51′03′′)

The streamflow-measurement station on

Sucker Run monitors streamflow from a 2.57-mi2

watershed, 11.6 percent of which is classified as

urban land use (U.S. Geological Survey, 1996).

Streamflow is not regulated above the station,

35.7 percent of the watershed is underlain by carbonate geology, and about 45 percent is covered by

forest. Just over half of the Sucker Run watershed

(53 percent) upstream from the station is in the

Piedmont Lowland Section of the Piedmont Physiographic Province. (Pennsylvania Department of

Transportation, 1997; Sevon, 2000). The remainder

of the watershed is in the Piedmont Upland Section. Two bridges, which are 227 ft apart, bound

the reach and may slightly constrict the bankfull

discharge. Sucker Run near Coatesville is a creststage, partial-record station that does not collect

continuous data but is operated primarily to document peak streamflow. Wading streamflow measurements usually are made throughout the

section of stream in which the cross-section surveys were conducted. High-water measurements

are made from the bridge immediately upstream

from the station.

Definition of the bankfull channel, in the

vicinity of the streamflow-measurement station,

was fair. Two cross sections were surveyed at riffles within the reach, and pebble counts were conducted within each to determine the particle

distribution. The stream reach containing both surveyed cross sections is shown in figure 6. The

bankfull widths, mean depths, and cross-sectional

areas of the two cross sections were averaged to

determine the input for the regional curves. The

bankfull water-surface elevation was extrapolated

to the outside vertical staff gage, with reasonable

certainty, to determine the gage height and streamflow associated with the bankfull stage. The channel geometry at the estimated bankfull discharge,

as indicated by streamflow-measurement data in

the USGS data base, was used to assist with confirmation of the bankfull selection.

Figure 6. View looking downstream at stream reach containing both surveyed

cross sections at Sucker Run near Coatesville, Pennsylvania.
11

USGS Station Number: 01639500

Stream Name: Big Pipe Creek

Location: at Bruceville, Maryland

(Lat 39°36′45′′, Long 77°14′10′′)

The streamflow-measurement station on Big

Pipe Creek monitors streamflow from a 102-mi2

watershed. Limited quantitative data describing

land use in the watershed are available. There is little or no effect from urban land use, regulation has

no appreciable effect on streamflow, there is no

apparent carbonate geology, and about 17 percent

of the watershed upstream from the station is covered by forest (R.W. James, Jr., U.S. Geological Survey, oral commun., 2001). About 32 percent of the

Big Pipe watershed upstream from the station is in

the Gettysburg-Newark Lowland Section of the

Piedmont Physiographic Province; the remainder

is in the Piedmont Upland Section. Big Pipe Creek

at Bruceville is a continuous streamflow-measurement station adjacent to a pool created by a lowprofile weir 25 ft downstream from the shelter.

A multi-span bridge is 300 ft upstream from the

station and does not appear to constrict the bankfull discharge. Wading streamflow measurements

usually are made upstream from the station. Highwater measurements are made from the bridge.

The site assessment was limited to one crosssection survey within the reach because of a storm

event and resulting elevated streamflow midway

through the assessment. The stream reach containing the surveyed cross section is shown in figure 7.

A pebble count was conducted within the cross

section to determine the particle distribution. The

bankfull channel clearly was defined throughout

most of the reach with the exception of within the

bridge right-of-way. The bankfull water-surface

elevation passed the outside vertical staff gage

from which the gage height and streamflow associated with the bankfull stage were determined. The

channel geometry at the estimated bankfull discharge, as indicated by measurement data in the

USGS database, was used to assist with confirmation of the bankfull selection.

Field evidence suggested by researchers

(Dunne and Leopold, 1978, Rosgen, 1996, Harrelson and others, 1994) as being indicative of the

bankfull channel was used at each station in the

initial identification of the bankfull channel. Stations where a clearly defined bankfull stage elevation passed through (for example, Manatawny

Creek near Pottstown and Big Pipe Creek at

Bruceville), or was extrapolated to (for example,

Figure 7. View looking upstream at stream reach containing the surveyed cross

section for Big Pipe Creek at Bruceville, Maryland.
12

Sucker Run near Coatesville and West Branch

Perkiomen Creek at Hillegas), the outside vertical

staff gage with reasonable certainty provided the

most confidence for the bankfull determination.

Stations where the bankfull stage was not clearly

defined in the vicinity of the streamflow-measurement station (for example, French Creek near

Phoenixville) required more emphasis on additional data for confirmation. Perkiomen Creek at

East Greenville, with fair definition of the bankfull

channel but no opportunity for comparison of

bankfull stage to the outside vertical staff gage,

required the most reliance on additional data for

confirmation of bankfull identification. Channel

geometry as indicated from streamflow measurements made at the station, streamflow computed

from cross-section characteristics, and determination of the sediment size being transported during

the bankfull discharge were used to assist with

confirmation of bankfull channel dimensions at all

stations.

Evaluation of the Regional Curves

The regional curves presented in figures 8

through 11 show the relation between drainage

area and bankfull cross-sectional area, bankfull

mean depth, bankfull width, and bankfull discharge, respectively. The 95-percent confidence

interval indicates a band within which there is a

95-percent probability that estimates of channel

geometry and streamflow for that particular drainage area will occur. The coefficient of determination, R2, is a measure of the variability in the

channel-geometry estimate accounted for by the

drainage area. Bankfull cross-sectional area (fig. 8)

and bankfull discharge (fig. 11) have the strongest

relation to drainage area as evidenced by R2 values

of 0.98. Both relations have a p-value less than

0.001, a residual standard error of 0.07 or less, and

a t-value for the drainage-area coefficient between

15.8 and 16.4. Users of these two regional curves

would expect to obtain the most reliable estimates.

The relation between bankfull mean depth and

drainage area (fig. 9) with an R2 of 0.84 and a

p-value less than 0.01 (residual standard error

= 0.11 and a t-value = 4.6) indicates a very strong

linear trend between all the stations except the one

with the smallest drainage area. The relation

between bankfull width and drainage area (fig. 10)

is the weakest of the four—R2 value of 0.79,

p-value less than 0.02, a residual standard error of

0.16, and a t-value for the drainage area coefficient

of 3.9.

Figure 8. Regional curve representing relation between bankfull cross-sectional area

and drainage area in non-urban, Lowland Sections of the Piedmont Physiographic

Province, Pennsylvania and Maryland.
13

Figure 9. Regional curve representing relation between bankfull cross-sectional mean

depth and drainage area in non-urban, Lowland Sections of the Piedmont Physiographic

Province, Pennsylvania and Maryland.

Figure 10. Regional curve representing relation between bankfull cross-sectional width

and drainage area in non-urban, Lowland Sections of the Piedmont Physiographic

Province, Pennsylvania and Maryland.
14

Regression diagnostics and visual inspection

of the relations in figures 8 through 11 indicate the

channel-characteristics data from the Sucker Run

station have a strong effect on all the regression

lines. Removing Sucker Run from the analysis

improved the strength of the correlation between

bankfull mean depth and drainage area as indicated by increasing the R2 to 0.99 (p-value < 0.001,

residual error = 0.02, and t-value for the drainage

area coefficient = 17.9). Removing Sucker Run from

the curves for bankfull discharge and bankfull

cross-sectional area resulted in a reduction of the

R2 values but at least 90 percent of the variability of

the data was explained by the drainage area. Without Sucker Run, the plot of bankfull channel width

is basically flat and shows essentially no slopinglinear relation to drainage area.

REFERENCE-REACH SELECTION

New stream-restoration designs for

impaired stream reaches frequently are based on a

series of measurements made at streams of similar

type that effectively accommodate streamflow and

sediment without excessive channel erosion or

deposition. The “stable” reach of stream, called a

reference reach, can be on a different reach of the

same stream as the project site or on a different

stream that has similar runoff characteristics and

valley type. Measurements at the reference reach

are directed at quantifying conditions of the bankfull channel. Measured channel characteristics are

presented as dimensionless ratios (for example,

width/depth ratio) and extrapolated to the project

site for incorporation into the restoration design.

Use of dimensionless ratios allows for the transfer

of channel characteristics among similar stream

types. By incorporating dimensionless ratios that

characterize an apparent stable reach of stream

into the restoration design, practitioners assume

the newly designed channel will function as effectively as the reference reach at transporting streamflow and sediment.

A 1,000-ft reach of stream that met all established criteria for a reference reach was identified

on Bermudian Creek, less than 1 mi upstream from

the project site. The location of the reference reach

and its proximity to the project site is shown on

figure 12. A representative riffle cross section in the

reference reach on Bermudian Creek is shown in

figure 13. Both the project site (14.8 mi2) and the

ference reach (11 mi2) are in the Gettysburg-Newark Lowland Section of the Piedmont Physiographic Province. Most of the Bermudian Creek

Figure 11. Regional curve representing relation between bankfull discharge and

drainage area in non-urban, Lowland Sections of the Piedmont Physiographic Province,

Pennsylvania and Maryland.
15

Figure 12. Location of project

site and reference reach on

Bermudian Creek, Adams

County, Pennsylvania.

Figure 13. View looking

downstream at cross section

526 of the reference reach on

Bermudian Creek, Adams

County, Pennsylvania.
16

watershed upstream from the project site (83 percent) and the reference reach (76 percent) is in the

Gettysburg-Newark Lowland Section of the Piedmont Physiographic Province. The remainder is in

the South Mountain Section of the Blue Ridge

Physiographic Province. Less than 1 percent of the

watershed upstream from the reference reach and

project site is classified as urban land use. Streamflow above the reference reach and the project site

is not regulated, geology is predominantly triassicaged sandstone, siltstone, shales, and diabase with

no carbonate rock, and about 29 percent of the

watershed is covered by forest.

The reference reach is heavily wooded, point

bars are well developed and vegetated, and excessive erosion or deposition is not evident. Riffles

and pools have heterogeneous distributions of

coarse- and fine-grained bed material. Geometry of

the bankfull channel is fairly consistent throughout

the reach. The bankfull channel is well defined

throughout most of the reach as indicated by a flattening of the bank to a flood-plain profile, changes

in depositional material, and the noticeable boundary of present woody and herbaceous vegetation.

Channel dimensions of the riffle cross sections

were applied to the Piedmont Lowland regional

curves to confirm bankfull identification.

Three riffle and three pool cross sections

were surveyed to define bank and channel characteristics. Pebble counts were conducted in each

cross section to determine the particle distribution

within the bankfull cross section. Representative

data that characterize each cross section are shown

in table 2. The longitudinal profile of the entire

1,000-ft reach was surveyed. Channel features

included in the survey were the thalweg (deepest

part of the stream), edge of water, bankfull elevations, and other major channel characteristics.

Channel-characteristic data from the longitudinal

profile and other reach descriptor data collected

during the site assessment are presented in table 3.

Procedures to collect and/or compute data contained in table 3 followed those outlined by Harrelson and others (1994) and Rosgen (1996).

COMPARISON OF ESTIMATES FROM

LOWLAND REGIONAL CURVES AND

DUNNE AND LEOPOLD REGIONAL

CURVES FOR REFERENCE-REACH

CHARACTERISTICS

The bankfull cross-sectional area of 90.1 ft2

estimated from the lowland regional curve for an

11-mi2 basin was 18 percent less than the estimate

from the Dunne and Leopold (1978) curve (110 ft2).

Estimates of bankfull mean depth (2.00 ft) and

bankfull width (44.7 ft) from the lowland regional

curves differ by about –33 and 15 percent, respectively, from the Dunne and Leopold estimates of

3.00 and 39.0 ft. The estimate of the bankfull

discharge from the lowland regional curve is

466 ft3/s. This estimate is 7 percent greater than the

Dunne and Leopold estimate of 436 ft3

/s.

Only cross-section surveys conducted within

riffles are applied to regional curves. All applicable

bankfull-channel dimensions, surveyed within the

reference reach, are within the 95-percent confidence interval on the lowland regional curves.

The measured bankfull cross-sectional area

for the three riffle cross sections at the reference

reach was less than estimates from the lowland

regional curve. All surveyed areas were within

-17 percent of the estimated value; the average difference was -16 percent. Measured bankfull crosssectional areas averaged 31 percent less than the

estimate from the Dunne and Leopold regional

curve for cross-sectional area of the bankfull channel.

The bankfull mean depth for all three riffle

cross sections at the reference reach ranged from

12 to 23 percent (average was 16.5 percent) less

than estimates from the lowland regional curve.

Measured bankfull mean depth averaged about

44 percent less than the estimate from the Dunne

and Leopold regional curve for mean depth of the

bankfull channel.

The bankfull widths measured at the three

riffle cross sections within the reference reach

ranged from 4 percent less to 9 percent more (average was 2 percent more) than estimates from the

lowland regional curve. Measured bankfull width

averaged about 17 percent less than the estimate

from the Dunne and Leopold regional curve for

bankfull width.
17

Table 2. Cross-section data collected from assessment of reference reach on Bermudian Creek, Adams County, Pennsylvania[ft, feet; ft2, feet squared; mm, millimeters; <, less than; +, actual width exceeds measured width; NA, not applicable]

Crosssection

station

number

 Riffle

or

pool

Rosgen

stream

type1

Bankfull

width

(ft)

Mean

bankfull

depth

(ft)

Maximum

bankfull

depth

(ft)

Bankfull

crosssectional

area

(ft2)

Width of flood

prone area1

(ft)

D15

(mm)

D35

(mm)

D50

(mm)

D84

(mm)

D95

(mm)

W

per

228 Riffle C4 45.0 1.70 2.33 76.4 190+ 0.1 7.6 15.0 96.0 211 4281 Riffle C4 42.9 1.76 2.11 75.5 88.4 .1 3.6 8.9 87.7 171 4367 Pool NA 41.5 1.51 3.23 62.6 NA <.1 2.0 12.0 39.2 81.6 4

526 Riffle C4 48.6 1.54 2.82 74.6 151+ .1 2.7 8.0 89.7 256 4758 Pool NA 32.7 2.02 3.26 66.0 NA .1 1.4 7.6 48.0 168 3

791 Pool NA 38.0 2.08 3.75 79.0 NA .4 11.1 26.4 140 233 4

1 Does not apply to pool cross sections.
18

Streamflows associated with each cross section at the reference reach were computed from

channel dimensions, representative channel roughness, and surface-water slope as surveyed

throughout the reach. The computed bankfull discharges for each cross section ranged from 389 to

401 ft3/s; the average was 394 ft3/s. The lowland

regional curve estimated 466 ft3/s for the bankfull

discharge in an 11.0-mi2 watershed, about 18 percent greater than the average at the reference reach.

The streamflow estimated from the Dunne and

Leopold regional curve for the bankfull discharge

(436 ft3/s) was 10.6 percent greater than the average computed streamflow for riffle cross sections at

the reference reach.

LIMITATIONS OF THE INVESTIGATION

The small number of stations available for

analysis is a major limiting factor in the strength of

the results of this investigation. Including additional data in each regression would provide a better estimate of the relations among bankfull

channel geometry, streamflow, and drainage area.

Additional data points would most likely reduce

the appreciable effect of Sucker Run. Subjective filtering criteria may have eliminated unnecessarily

the streamflow-measurement stations that could

have been included in the regional curves. Conversely, the land-use percentages characterizing

the watershed may effect runoff characteristics at a

much lower percentage than the criteria would

indicate. For example, numerous studies suggest

channel stability may be affected by urban land

use and regulation at percentages lower than the

20 percent used in this report. As additional

streamflow-measurement stations in the Piedmont

Upland Section are assessed, the estimates provided by the relations of channel characteristics

and drainage in the Lowland Sections of the Piedmont Physiographic Province may be improved by

including these data. Statistical tests could be used

to determine if the differences in runoff characteristics warrant separate regional curves for the

Upland Section and the two Lowland Sections of

the Piedmont Physiographic Province or if one allinclusive regional curve is appropriate.

The regional curves presented here should

only be used for the confirmation of the bankfull

channel at streams in the Lowland Sections of the

Piedmont Physiographic Province. The assumption made for this investigation is that the bankfull

discharge is within the 1- to 2-year recurrenceinterval range. Thorne and others (1997) state “the

widely reported assertion that bankfull discharge

occurs on average once every 1 to 2 years is now

seen as an oversimplification.” If runoff patterns at

a streamflow-measurement station are such that

the bankfull discharge may occur more often than

this 1- to 2-year frequency, the recurrence-interval

criteria did not substantiate identification of the

bankfull channel as it was intended. In addition,

land use and other basin characteristics upstream

from the reach in consideration should be similar

to those used for the selection criteria in this

assessment.

Table 3. Longitudinal-profile data collected from assessment of

reference reach on Bermudian Creek, Adams County, Pennsylvania

[ft, feet; ft/ft, feet per foot; <, less than]

Reach length

(ft)

Bankfull slope

(ft/ft) Sinuosity Valley slope(ft/ft)

1,000 0.008 1.12 0.008

Average riffle

slope

(ft/ft)

Average

pool slope

(ft/ft)

Average poolto-pool

spacing

(ft)

Average

meander

length

(ft)

Average radius

of curvature

(ft)

Average belt

width

(ft)

0.016 0.001 93.0 149 126 77.0

Riffle slope

range

(ft/ft)

Pool slope

range

(ft/ft)

Pool-to-pool

spacing range

(ft)

Meander

length range

(ft)

Radius of

curvature

range

(ft)

Belt width

range

(ft)

0.008 - 0.026 <0.001 - 0.003 39.0 - 150 105 - 248 60.0 - 340 44.0 - 100
19

With regard to the reference reach, the qualitative designation of stability for the stream reach,

without monitoring over time, may be inaccurate.

The incorrect designation of the reference reach as

a stable channel may introduce errors into the

project design that is so closely related to the reference reach and its assumed stability. Use of these

reference-reach data should be limited to project

sites in areas having similar runoff characteristics

and valley type.

SUMMARY AND CONCLUSIONS

The USGS, in cooperation with PaDEP, conducted a study to develop regional curves and

characterize a reference reach. This study took

place from 1999-2000 in the Lowland Sections of

the Piedmont Physiographic Province in Pennsylvania and Maryland. A regional curve is a valuable

tool used to confirm the identification of the bankfull channel. Regional curves were developed from

channel-geometry and streamflow data collected at

six USGS streamflow-measurement stations in the

Gettysburg-Newark Lowland and Piedmont Lowland Sections of the Piedmont Physiographic Province (Manatawny Creek near Pottstown, Pa.–

01471980, French Creek near Phoenixville, Pa.–

01472157, Perkiomen Creek at East Greenville, Pa.–

01472198, West Branch Perkiomen Creek at Hillegas, Pa.–01472199, Sucker Run near Coatesville,

Pa.–01480610, Big Pipe Creek at Bruceville, Md.–

01639500). The range in size of watersheds monitored by these stations is 2.57 to 102 mi2. The bankfull channel was identified at each station by use of

field indicators and confirmed by use of historical

streamflow-measurement data. Representative

cross sections were surveyed in riffles. Width,

mean depth, and cross-sectional area of the bankfull channel were plotted as a function of drainage

area and a “best-fit” regression line was applied to

the data. The resulting regression line, and the corresponding equation defining that line, can be

used to estimate the dimensions and streamflow of

the bankfull channel at stream sites having similar

runoff characteristics throughout the two Piedmont Lowland Sections when the drainage area is

known.

A reference reach is a segment of a stream

channel that appears to be effectively accommodating streamflow and sediment without excessive

channel erosion or deposition. Channel characteristics defining a reference reach in the lowland sections of the Piedmont will serve as a template for

design of a stream-restoration project on an

impaired reach of Bermudian Creek. A reference

reach meeting established criteria was identified

on Bermudian Creek, less than 1 mi upstream from

the proposed stream-restoration site. Surveys of

multiple cross sections and the longitudinal profile

of the stream were conducted to characterize that

channel. Bankfull channel dimensions of cross-sectional area (range = 62.6 to 79.0 ft), width

(range = 32.7 to 48.6 ft), and mean depth

(range = 1.51 to 2.08 ft) varied throughout the

reach. The particle distribution of the streambed

material within each cross section was determined.

Median particle size in each cross-section ranged

from 7.6 to 26.4 millimeters. Monitoring changing

channel characteristics over time is essential to

confirm or refute the designation of “stable.”

The concepts of regional curves and reference reaches can be valuable tools to support

efforts in stream restoration. Practitioners of

stream restoration need to recognize them as such

and realize their limitations. Regional curves provide an estimate of bankfull-channel dimensions

and streamflow. The curves developed for this

study are based on limited highly variable data.

The small number of streamflow-measurement stations used in these regressions limits the strength

of the regional curves presented.

The use of channel-characteristics data from

a reference reach without any monitoring data to

document the stability of the reference reach over

time is a topic of debate. Applying qualitative criteria to a selected reach of stream in an attempt to

designate stability is subject to interpretation. In

the early stages of stream restoration utilizing natural stream design, few other options are available.

With the emphasis on the reference reach as a template for design, an enhanced network of stream

reaches where long-term monitoring data are collected is essential to quantitatively document

stream condition and improve confidence in the

stability of the selected reference.
20

SELECTED REFERENCES

Alexander, R.B., Brakebill, J.W., Brew, R.E., Smith,

R.A., 1999, ERF1—Enhanced River Reach

File 1.2 [online]: U.S. Geological Survey

Open-File Report 99-457 [accessed May 17,

2001, at URL http://water.usgs.gov/GIS/

metadata/usgswrd/erf1.html].

Andrews, E.D., 1980, Effective and bankfull

discharges of streams in the Yampa River

Basin, Colorado and Wyoming: Journal of

Hydrology, v. 46, p. 311-330.

Dunne, T., and Leopold, L.B., 1978, Water in

Environmental Planning: San Francisco,

Calif., W.H. Freeman, 818 p.

Federal Interagency Stream Restoration Working

Group, 1998, Stream corridor restoration,

principles, processes, and practices: GPO

Item No. 0120-A; SuDocs No. A 57.6/2:EN

3/PT.653. ISBN-0-934213-59-3.

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

1992, Stream hydrology, an introduction for

ecologist: Chichester, England, John Wiley

and Sons, 526 p.

Hammer, T.R., 1972, Stream channel enlargement

due to urbanization: Water Resources

Research, v. 8, p. 1,530-1,540.

Harrelson, C.C., Rawlins, C.L., and Potyondy, J.P.,

1994, Stream channel reference sites—An

illustrated guide to field technique: U.S.

Forest Service, General Technical Report

RM-245, 61 p.

Leopold, L.B., 1994, A view of the river:

Cambridge, Mass., Harvard University

Press, 298 p.

Pennsylvania Department of Transportation, 1997,

1997 Pennsylvania cartographic/GIS

information: Harrisburg, Pa., Bureau of

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