U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2007–5162

Prepared in cooperation with the Virginia Coastal Zone Management Program and the 

Virginia Department of Conservation and Recreation Coastal Nonpoint Source Pollution 

Control Program

Bankfull Regional Curves for Streams in the Non-Urban, 

Non-Tidal Coastal Plain Physiographic Province, 

Virginia and Maryland
Cover.  Bush Mill Stream. View looking upstream from the bridge on State Highway 601 near Heathsville, Virginia (photograph taken 

by Jennifer L. Krstolic, U.S. Geological Survey, April 15, 2005).
Bankfull Regional Curves for Streams in the 

Non-Urban, Non-Tidal Coastal Plain Physiographic 

Province, Virginia and Maryland

By Jennifer L. Krstolic and Jeffrey J. Chaplin

Prepared in cooperation with the Virginia Coastal

 Zone Management Program and the 

Virginia Department of Conservation and Recreation

 Coastal Nonpoint Source Pollution Control Program

Scientific Investigations Report 2007–5162

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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Suggested citation:

Krstolic, J.L., and Chaplin, J.J., 2007, Bankfull regional curves for streams in the non-urban, non-tidal Coastal Plain 

Physiographic Province, Virginia and Maryland: U.S. Geological Survey Scientific Investigations Report 2007–5162, 

48 p. (available online at http://pubs.water.usgs.gov/sir2007–5162)
iii

Contents

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

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

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

Description of Study Area ...................................................................................................................2

Development of Coastal Plain Bankfull Regional Curves........................................................................4

Site Selection.........................................................................................................................................4

Basin Characteristics...........................................................................................................................5

Field Data Collection.............................................................................................................................6

Surveys of the Bankfull Channel ...............................................................................................7

Pebble Counts ..............................................................................................................................8

Bankfull Discharge ......................................................................................................................8

Comparison Surveys of Maryland Sites...................................................................................9

Analysis of Bankfull Channel Data.....................................................................................................9

Comparison of Coastal Plain Regressions for Maryland, North Carolina, and Virginia 

Stations ...................................................................................................................................11

Coastal Plain Regional Curves..........................................................................................................15

Limitations............................................................................................................................................19

Summary........................................................................................................................................................20

Acknowledgments.......................................................................................................................................21

References Cited..........................................................................................................................................21

Appendix 1—Streamflow-Gaging Station Numbers, Site Descriptions and Photographs, 

Longitudinal Profiles, Riffle Cross Sections, and Bed Material Particle-Size 

Distributions of Cross Sections....................................................................................................23

Figures

1. Map of site locations in Virginia, Maryland, and Delaware in the Coastal Plain 

Physiographic Province...............................................................................................................3

2. A flood plain wetland at the Cat Point Creek study site in Virginia ......................................6

3. Bankfull features representing the top of the bank at Mill Creek in Maryland..................7

4. Bankfull bench or point bar along the right bank of Cat Point Creek in Virginia................7

5. Log-log plot of three regressions of bankfull cross-sectional area and drainage 

area for streams in the Coastal Plain Physiographic Province in Maryland, 

Virginia, and North Carolina......................................................................................................12

6. Log-log plot of three regressions of bankfull width and drainage area for streams 

in the Coastal Plain Physiographic Province in Maryland, Virginia, 

and North Carolina .....................................................................................................................12

7. Log-log plot of three regressions of bankfull mean depth and drainage area 

for streams in the Coastal Plain Physiographic Province in Maryland, Virginia, 

and North Carolina .....................................................................................................................13

8. Log-log plot of three regressions of estimated bankfull discharge and drainage 

area for streams in the Coastal Plain Physiographic Province in Maryland, 

Virginia, and North Carolina......................................................................................................13
iv

9. Regional curve relating bankfull cross-sectional area to drainage area 

for streams in the non-urban, non-tidal Coastal Plain Physiographic Province 

of Virginia and Maryland ...........................................................................................................16

10. Regional curve relating bankfull width to drainage area for streams in the 

non-urban, non-tidal Coastal Plain Physiographic Province of Virginia 

and Maryland ..............................................................................................................................16

11. Regional curve relating bankfull mean depth to drainage area for streams in 

the non-urban, non-tidal Coastal Plain Physiographic Province of Virginia 

and Maryland ..............................................................................................................................17

12. Regional curve relating estimated bankfull discharge to drainage area 

for streams in the non-urban, non-tidal Coastal Plain Physiographic Province 

of Virginia and Maryland ...........................................................................................................17

13. Regression residuals for regional curves relating drainage area to bankfull 

cross-sectional area and box plot of the distribution of residuals for bankfull 

cross-sectional area ..................................................................................................................18

14. Regression residuals for regional curves relating drainage area to bankfull width 

and box plot of the distribution of residuals for bankfull width...........................................18

15. Regression residuals for regional curves relating drainage area to bankfull mean 

depth and box plot of the distribution of residuals for bankfull mean depth....................19

16. Regression residuals for regional curves relating drainage area to estimated 

bankfull discharge and box plot of the distribution of residuals for estimated 

bankfull discharge ......................................................................................................................19

Tables

1. Streamflow-gaging stations used for development of regional curves for the 

Coastal Plain Physiographic Province in Virginia and Maryland .........................................5

2. Basin characteristics for streamflow-gaging stations surveyed during this study 

for development of regional curves for the Coastal Plain Physiographic Province 

in Virginia and Maryland .............................................................................................................6

3. Duplicate-survey results from stream bankfull channel geometry surveys at two 

streamflow-gaging stations in Maryland..................................................................................9

4. Bankfull channel geometry data collected for this study in streams in the 

Coastal Plain Physiographic Province in Virginia and Maryland .......................................10

5. Bankfull channel geometry data collected by McCandless (2003) in streams 

in the Coastal Plain Physiographic Province in Maryland...................................................14

6. Equations and diagnostic statistics for regional curves relating drainage area 

to bankfull discharge and bankfull channel geometry for streams in the Coastal 

Plain Physiographic Province in Virginia and Maryland......................................................15
v

Conversion Factors

SI to Inch/Pound

Multiply By To obtain

Length

centimeter (cm) 0.3937 inch (in.)

millimeter (mm) 0.03937 inch (in.)

meter (m) 3.281 foot (ft) 

kilometer (km) 0.6214 mile (mi)

Area

square centimeter (cm2) 0.001076 square foot (ft2)

square meter (m2) 10.76 square foot (ft2) 

hectare (ha) 0.003861 square mile (mi2

) 

square kilometer (km2) 0.3861 square mile (mi2)

Volume

cubic decimeter (dm3) 0.03531 cubic foot (ft3) 

cubic meter (m3) 35.31 cubic foot (ft3)

Flow rate

meter per second (m/s) 3.281 foot per second (ft/s) 

cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s)

Vertical coordinate information is referenced to the North American Vertical Datum 

of 1988 (NAVD88).

Horizontal coordinate information is referenced to the North American Datum 

of 1927 (NAD27).

Abstract

Natural-channel design involves constructing a stream 

channel with the dimensions, slope, and plan-view pattern 

that would be expected to transport water and sediment and 

yet maintain habitat and aesthetics consistent with unimpaired 

reaches. The adequate description of channel geometry in 

unimpaired reaches often is an important component of 

natural-channel design projects and can be facilitated through 

empirical regression relations, or regional curves, relating 

bankfull geometry to drainage area. One-variable, ordinary 

least-squares regressions relating bankfull discharge, bankfull 

cross-sectional area, bankfull width, and bankfull mean depth 

to drainage area were developed based on data collected at 

20 streamflow-gaging stations in Virginia and Maryland. 

These regional curves can be used to estimate the bankfull 

discharge and bankfull channel geometry when the drainage 

area of a watershed is known. 

Field data collected at the site for each streamflow-gaging 

station included one longitudinal profile of bankfull features 

and channel-bed slope, two riffle cross-section surveys of 

channel geometry, cross-section pebble counts, and one site 

sketch with photographs of the channel and bankfull features. 

The top of the bank was the bankfull feature most indicative 

of bankfull geometry. Field data were analyzed to determine 

bankfull cross-sectional area, bankfull width, bankfull mean 

depth, and D50- and D84-particle sizes for the two riffles at 

each site. The bankfull geometry from the 8 sites surveyed 

during this study represents the average of two riffle cross 

sections for each site, and the bankfull geometry from the 

12 Maryland sites represents one cross section for each site. 

Regional curves developed for the 20 sites had coefficient of 

determination (R2) values of 0.945, 0.890, 0.871, and 0.793 

for bankfull cross-sectional area, width, mean depth, and 

discharge, respectively. The regional curves represent conditions for streams with defined channels and bankfull features 

in Virginia and Maryland with drainage areas ranging from 

0.28 to 113 square miles. All sites included in the development 

of the regional curves were located on streams with U.S. 

Geological Survey streamflow-gaging stations. These curves 

can be used to verify bankfull features identified in the field 

and bankfull stage for ungaged streams in non-urban areas.

Introduction

Rebuilding physically degraded stream channels has 

become a key element in the management of surface-water 

resources throughout the Nation. Driven largely by Section 

404 of the Clean Water Act, many states are required to 

remedy excess stream-channel adjustment that commonly 

results from alteration of flows or sediment supply in a 

watershed. Restoration of stream channels that have excessive 

erosion, deposition, or degraded habitat is commonly proposed 

and implemented by Federal, state, local, or private organizations in an effort to return the channels to more stable and 

biologically productive conditions. Traditional engineering 

practices for stream stabilization frequently rely on hardening 

the stream channel with rip-rap, gabions, concrete, or other 

countermeasures in reaches that are subjected to erosive 

forces. Stream restoration efforts that utilize natural-channel 

design techniques—with the philosophy of working in concert 

with stream processes rather than resisting them—have 

become common practice in the eastern United States and 

elsewhere (2007). Natural-channel design involves rebuilding 

a channel with the dimensions, slope, and plan-view pattern 

that is expected to transport water and sediment without excessive aggradation or degradation while maintaining habitat and 

aesthetics consistent with unimpaired reaches subjected to 

similar hydrologic conditions (Rosgen, 1996). 

For those subscribing to this approach, the notion of a 

bankfull channel is the cornerstone concept. Many naturalchannel designs are based on the geometry of the bankfull 

channel and the discharge occurring when the bankfull 

channel is flowing full. Although the bankfull channel is 

formed by a wide range of flows (Emmett, 2004), moderate 

flows, with recurrence intervals commonly ranging from 1 to 

2 years, do more work in terms of sediment redistribution than 

Bankfull Regional Curves for Streams in the Non-Urban, 

Non-Tidal Coastal Plain Physiographic Province, 

Virginia and Maryland 

By Jennifer L. Krstolic and Jeffrey J. Chaplin
extreme high flows, which occur less frequently (Wolman and 

Miller, 1960; Dunne and Leopold, 1978). For the purposes of 

this report, the bankfull discharge is defined as the flow that 

represents, or is a surrogate for, the full range of flows forming 

the bankfull channel.

Bankfull discharge and bankfull channel geometry are 

highly correlated with drainage area (Dunne and Leopold, 

1978). Empirical regression relations, or regional curves, have 

recently been developed to estimate bankfull geometry in the 

Valley and Ridge Physiographic Province of Virginia (Keaton 

and others, 2005), the Atlantic Coastal Plain Physiographic 

Province (Coastal Plain) of Maryland (McCandless, 2003), 

the Coastal Plain of North Carolina (Doll and others, 2003), 

and elsewhere in the eastern United States (McCandless and 

Everett, 2002; Dudley, 2004; Chaplin, 2005; Sherwood and 

Huitger, 2005; Westergard and others, 2005). These bankfull 

regional curves are one-variable ordinary least-squares regressions relating bankfull discharge, bankfull cross-sectional 

area, bankfull width, and bankfull mean depth to drainage 

area in settings that are expected to have mostly homogenous 

hydrologic characteristics. Regression equations describing 

the regional curves can be used to estimate the discharge and 

geometry of a natural bankfull channel when drainage area of 

a watershed is known. 

At the beginning of this study, no regional curves 

were available for the Coastal Plain of Virginia, and the 

applicability of curves developed in coastal areas of Maryland 

(McCandless, 2003) and North Carolina (Doll and others, 

2003) in Virginia was not known. In support of streamrestoration activities, regional curves for bankfull geometry 

can be used to verify field identification of bankfull features 

in ungaged streams. As part of an ongoing effort to support 

stream restoration and natural-channel design endeavors in 

Virginia, the U.S. Geological Survey (USGS), in cooperation 

with the Virginia Coastal Zone Management Program and the 

Virginia Department of Conservation and Recreation (DCR) 

Coastal Nonpoint Source Pollution Control Program, began 

development of bankfull regional curves for use in non-urban, 

non-tidal coastal areas of Virginia in 2005. 

Purpose and Scope

The purpose of this report is to present the data for 

and results of bankfull regional curve development in the 

non-urban, non-tidal Coastal Plain of Virginia and Maryland. 

Bankfull geometry was surveyed in 2005–2006, and bankfull 

discharge was calculated at six streamflow-gaging stations 

and associated stream reaches (sites) in Virginia and two sites 

on the Delmarva Peninsula of Maryland. Because regression 

relations are more robust when the sample size is large (Helsel 

and Hirsch, 2002), data from these 8 sites were combined with 

data from 12 sites previously surveyed in Maryland (McCandless, 2003) for the development of bankfull regional curves. 

Description of Study Area

The Coastal Plain includes portions of all the states that 

border the Atlantic Ocean from Maine to Florida. The portion 

of the Coastal Plain of interest in this investigation includes 

parts of Virginia; Maryland; Delaware; Washington, DC; 

and North Carolina east of the Fall Line—the transition area 

between the Piedmont Physiographic Province and the Coastal 

Plain. The streams in the Piedmont Physiographic Province 

flow over resistant bedrock, which transitions into more easily 

eroded sediments in the Coastal Plain, producing numerous 

rapids, or falls at the boundary. While most of the data were 

collected in Virginia and Maryland (fig. 1), the potential 

transferability of regional curves within the Coastal Plain may 

prove useful to the stream restoration community. The portion 

of the Coastal Plain included in this investigation is an area 

of approximately 39,900 square miles (mi2). Fifty Virginia 

counties and independent cities lie entirely or partially within 

the Coastal Plain, approximately 22 percent of the total land 

area in Virginia. Eighteen Maryland counties, 3 Delaware 

counties, 44 North Carolina counties, and Washington, DC, lie 

entirely or partially within the Coastal Plain. 

According to the 2000 census (U.S. Census Bureau, 

2004 a, b, c, d), approximately 13 million people live in the 

Coastal Plain in Delaware (4.5 million), Virginia (3.3 million), 

Maryland (2.5 million), North Carolina (2.4 million), and 

Washington, DC (0.3 million). The majority of people are 

concentrated in large urban areas, including the northern 

Virginia and western Maryland metropolitan areas near 

Washington, DC; the cities of Fredericksburg, Richmond, and 

the localities that collectively make up the Hampton Roads 

metropolitan area in Virginia; Baltimore, Annapolis, and 

Ocean City in Maryland; and Dover, Delaware. The remainder 

of the Coastal Plain is relatively sparsely populated, ranging 

from small towns to outlying non-urban areas composed of 

forest and agricultural land. 

The climate of the region is temperate and humid, with 

a mean annual precipitation of approximately 43 inches 

(National Climate Data Center, 2005). The majority of 

precipitation falls during the months of May, June, July, and 

August (Daly, 1998).

The Coastal Plain is defined geologically by the underlying, mostly unconsolidated sediments of fluvial-deltaic and 

marine origin that thin toward their western limit near the Fall 

Line, where the Coastal Plain sediments meet the crystalline 

rock of the Piedmont Physiographic Province (Fenneman, 

1938). In Virginia, a number of major rivers drain eastward 

into the Chesapeake Bay, most of which become brackish and 

tidal as they enter estuaries east of the Fall Line. From north to 

south, these rivers include, the Potomac River, Rappahannock 

River, York River, and James River. South of the Chesapeake 

Bay, the Nottoway and Meherrin Rivers flow through Virginia, 

into North Carolina, and into the Atlantic Ocean. 

 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
02042710

02042250

01674700

01674200

01668500

01661800

01594526

01661500

01661050

01492500

01485500

01487000

01484000

01492550

01658000 01492050

01661430

01491000 01484100

Richmond

Fredericksburg

Dover

Annapolis

Baltimore

01489000

ATLANTIC OCEAN

CHESAPEAKE BAY

James

River

Potomac

River

River

River

York

Rappahannock

Nottoway

Meherrin

River

River

Washington, D.C.

Middle Peninsula

York-James Peninsula

Northern Neck

Delmarva Peninsula DELAWARE MARYLAND

MARYLAND

VIRGINIA

Ocean City

Eastern Shore

79 ̊ 78 ̊ 77 ̊ 76 ̊ 75 ̊

39 ̊38 ̊37 ̊

0 10 20 MILES

0 10 20 KILOMETERS

Fall

Line

Fall

Line

COASTAL PLAIN

PIEDMONT

APPALACHIAN

BLUE RIDGE

PLATEAU

VALLEY

AND

RIDGE

Line Fall

EXPLANATION

Drainage basinCoastal Plain PhysiographicProvinceMcCandless (2003)Current study

Base, state boundaries, and physiographic province boundaries from U.S. Geological Survey  Digital Line Graph, 1:2,000,000, 1987Universal Transverse Mercator 18 Projection, NAD27, Central Meridian 75o00’WHydrography from U.S. Environmental Protection Agency Reach File Version 1.0, 1:100,000, 1996City locations from U.S. Census Cartographic Boundary Files, Consolidated Cities, 1:500,000, 2000Virginia watersheds from Hayes and Wiegand (2006), 1:24,000Maryland watersheds delineated from U.S. Geological Survey Digital Raster Graphics, 1:24,000

Figure 1. Site locations in Virginia, Maryland, and Delaware in the Coastal Plain Physiographic Province.

Introduction 
The topography of the Virginia Coastal Plain is characterized by rolling terrain with deeply incised stream valleys 

in the northwestern section and by gently rolling to level 

terrain with broad stream valleys in the eastern and southern 

sections (McFarland and Bruce, 2006). Detailed information 

about the underlying geology and aquifer system in Virginia 

is available in McFarland and Bruce (2006). Land-surface 

elevations decline seaward, ranging from over 300 feet (ft) 

above the North American Vertical Datum of 1988 (NAVD88) 

in the western Coastal Plain to sea level at the Atlantic coast. 

The mean land-surface elevation in the Coastal Plain in 

Virginia; Maryland; Washington, DC; and Delaware is 75.5 ft 

(U.S. Geological Survey, 2001). On the eastern side of the 

Chesapeake Bay, the land is referred to as the Eastern Shore in 

Virginia or the Delmarva Peninsula in Delaware and Maryland 

(fig. 1). 

Development of Coastal Plain Bankfull 

Regional Curves

Six sites at streamflow-gaging stations in Virginia 

were surveyed, and 14 sites at streamflow-gaging stations in 

Maryland (surveyed by McCandless, 2003) were added to 

the dataset to develop regional curves for the Coastal Plain in 

Virginia and Maryland. Two sites from McCandless (2003) 

were re-surveyed during this study to verify results. Both field 

surveys and historical discharge data were used for bankfull 

identification. Detailed longitudinal and cross-sectional 

surveys of bankfull features at each site were used to calculate 

the bankfull channel geometry. The stage associated with the 

1- to 2-year recurrence interval was used as a guide for field 

identification of bankfull features, although the true bankfull 

features may be higher or lower than that stage (Williams, 

1978; Richards, 1982; Knighton, 1998). After surveys were 

completed, historical data were used to calculate the bankfull 

discharge for field-identified bankfull features. The bankfull 

cross-sectional area, bankfull width, bankfull mean depth, 

and bankfull discharge were regressed with drainage area by 

using the ordinary least squares method to construct bankfull 

regional curves. 

Site Selection

Sites were selected by following criteria found in recent 

similar studies (Cinotto, 2003; McCandless, 2003; Chaplin, 

2005; Keaton and others, 2005). Streams considered for this 

study showed few human alterations, such as channelization, 

dredging, or manmade bank stabilization structures. However, 

the existence of a streamflow-gaging station indicates 

some past human alteration to the stream, usually through 

the construction of a bridge or culvert to which the gage 

is attached. All streams with active or discontinued USGS 

streamflow-gaging stations in the Coastal Plain of Virginia 

were evaluated against seven selection criteria:

At least 10 years of peak-flow data, 

Recoverable benchmarks referenced to staff gage 

elevations,

Non-tidal flow conditions, 

Drainage basin area less than 250 mi2, 

Drainage basin land use less than 20 percent urban, 

Flow regulated from less than 10 percent of the drainage area, and 

Stream reach exhibiting consistent bankfull features 

over a length of approximately 20 bankfull channel 

widths. 

Six out of 51 Virginia sites met all seven selection 

criteria. Fifty-one streamflow-gaging stations met the peakflow data criteria. Of the 51, 12 sites were excluded because 

the drainage areas were too large, and 11 sites were excluded 

because the land use in the basin was more than 20-percent 

urbanized. Twenty-five sites were visited to determine if 

bankfull features were identifiable. East of the Fall Line and 

at close proximity to the Chesapeake Bay, streams at low 

elevations often were tidal. Nine stream sites that were visited 

had flood plains filled with dense wetlands with undefined 

channel geometry. The primary reason they did not meet the 

selection criteria was the lack of consistent bankfull features. 

Streams in the Coastal Plain often transition between swamps 

with no identifiable channels and streams with identifiable 

channels. Streamflow-gaging stations often are installed at 

the short stretches where the flows are constricted by bridges 

or culverts. Examples include Dragon Swamp at Mascot 

(01669520), Seacock Creek near Ivor (02048400), and multiple sites on Cypress Swamp (02043500 and 02049700). Even 

though peak-flow data were available, there simply were not 

channel forms that met the classification criteria for this study. 

Other streams recently had experienced catastrophic events, 

such as a 200-year flood at Totopotomy Creek (01673550) that 

modified the channel geometry. Field observations suggest that 

recent hurricanes altered the geometry of many of the Coastal 

Plain streams making identification of bankfull features 

questionable. 

The dearth of appropriate sites in Virginia prompted the 

inclusion of sites from Maryland (table 1). Fourteen sites in 

Maryland had previously been surveyed and were included in 

regional curves for the Coastal Plain of Maryland (McCandless, 2003). Although these sites meet the selection criteria set 

forth in this study, two were selected for duplicate surveys to 

compare results before the data from this study were combined 

with data from McCandless (2003). 

•

•

•

•

•

•

•

 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
Basin Characteristics

Basin characteristics were derived to characterize basinspecific details about the land use, elevation, and precipitation 

regime of the sites surveyed during this investigation. Digital 

representations of the basin boundaries in this study were 

delineated for the six Virginia sites as part of an update of 

USGS drainage-basin areas for streamflow-gaging stations in 

Virginia (Hayes and Wiegand, 2006). The same methodology 

was followed for the two Maryland sites that were re-surveyed 

as part of this study. The digital basin-boundary geographic 

information system (GIS) layers for the eight sites surveyed 

during this study were used to extract basin characteristics for 

land use, mean elevation, and mean annual precipitation. A 

land-use raster dataset (30-meter (m) resolution) representing 

the year-2000 conditions (Goetz and others, 2004) was used to 

calculate the percent forest and percent wetland for each basin. 

The National Elevation Dataset (30-m resolution) was used to 

calculate mean elevation (U.S. Geological Survey, 2001). An 

average-annual precipitation vector dataset (4-kilometer (km) 

accuracy) derived from the Parameter-Elevation Regressions 

on Independent Slopes Model (PRISM) climate mapping 

system (Daly, 1998) was used to calculate mean annual 

precipitation for each basin.

Six sites were located on the western side of the 

Chesapeake Bay in Virginia, and two sites were located on 

the Delmarva Peninsula of Maryland. The sites range in size 

from 0.28 mi2 to 113 mi2 (table 2). The land-surface elevation 

Table 1. Streamflow-gaging stations used for development of regional curves for the Coastal Plain 

Physiographic Province in Virginia and Maryland. 

[mi2, square miles; ddmmss, degrees, minutes, seconds; NAD27, North American Datum of 1927; CSG, crest-stage gage;

CRG, continuous-record gage]

Station name Station 

number

Drainage 

area 

(mi2)

Period of 

record

Station 

type

Latitude 

NAD27

(dd mm ss)

Longitude 

NAD27

(ddmmss)

Data from the current study

Collins Run Tributary near Providence Forge, VA 02042710 0.28 1965–1975 CSG 372415 -770250

Bailey Branch Tributary at Spring Grove, VA 02042250 .71 1967–2004 CSG 371029 -765913

Mill Creek near Skipton, MDa 01492550 4.6 1966–1975 CSG 385500 -760342

Aylett Creek at Aylett, VA 01674700 6.17 1969–1995 CSG 374705 -770623

Bush Mill Stream near Heathsville, VA 01661800 6.82 1963–2005 CRG 375236 -762942

Reedy Creek near Dawn, VA 01674200 16.8 1951–2005 CSG 375255 -772135

Cat Point Creek near Montross, VA 01668500 45.6 1935–1999 CRG 380223 -764938

Choptank River near Greensboro, MDa 01491000 113 1948–2003 CRG 385950 -754709

Data from McCandless (2003)

Glebe Branch at Valley Lee, MD 01661430 0.3 1968–1978 CSG 381140 -763113

Beaverdam Branch at Houston, DE 01484100 2.8 1958–2006 CRG 385420 -753047

Mill Creek near Skipton, MD 01492550 4.6 1966–1976 CSG 385500 -760342

Faulkner Branch at Federalsburg, MD 01489000 7.1 1950–1992 CRG 384244 -754734

Sallie Harris Creek near Carmichael, MD 01492500 8.1 1951–2006 CRG 385753 -760633

Gravel Run at Beulah, MD 01492050 8.4 1966–1975 CSG 384054 -755353

Murderkill River near Felton, DE 01484000 13.6 1931–1999 CRG 385833 -753403

St. Clements Creek near Clements, MD 01661050 18.5 1968–2006 CRG 381959 -764331

St. Mary’s River at Great Mills, MD 01661500 24 1946–2005 CRG 381430 -763014

Nassawango Creek near Snow Hill, MD 01485500 44.9 1949–2007 CRG 381344 -752819

Mattawoman Creek near Pomonkey, MD 01658000 54.8 1949–2007 CRG 383546 -770323

Nanticoke River near Bridgeville, DE 01487000 75.4 1935–2006 CRG 384342 -753344

Western Branch at Upper Marlboro, MD 01594526 89.7 1985–2007 CRG 384851 -764456

Choptank River near Greensboro, MD 01491000 113 1948–2007 CRG 385950 -754710

a

 These streamflow-gaging stations were also surveyed by McCandless (2003) for the development of regional curves in the

Maryland Coastal Plain. They were re-surveyed to establish whether the surveying techniques used in this study produced results

similar to surveys conducted by McCandless (2003).

Development of Coastal Plain Bankfull Regional Curves 
in the Coastal Plain in Virginia; Maryland; Washington, DC; 

and Delaware ranges from 11.5 ft to 252 ft, with a mean 

elevation of 75.5 ft (U.S. Geological Survey, 2001). The mean 

elevation for each basin ranged from 52.0 ft to 196.7 ft above 

NAVD88. Seventy-five percent of mean elevations for each 

basin were higher than the mean elevation of the Coastal 

Plain in the study area. The minimum elevation for each basin 

ranged from 11.5 ft to 94.5 ft above NAVD88. Two sites had 

minimum elevations that were higher than the mean elevation 

of the Coastal Plain. All sites were non-tidal and higher on the 

landscape than many streams in the Coastal Plain. 

The sites all exhibit fairly well-defined crosssectional geometry, while many low-lying coastal 

water courses, whether tidal or not, do not exhibit 

these characteristics. Mean annual precipitation 

at the sites was about 43 inches (in.), except 

for Bailey Branch Tributary near Spring Grove, 

Virginia, which had a mean annual precipitation 

of about 45 in. (table 2).

Basin land use was dominated by forest, with 

all but one basin having more than 50-percent 

forested land (table 2). Mill Creek has 13.6-

percent forested land and 80-percent agricultural 

land. An average of 4 percent of each basin land 

use was wetland as classified in Goetz and others 

(2004). The National Wetlands Inventory reported 

an average of 6 percent of each basin land use as 

wetland (U.S. Fish and Wildlife Service, 1979). 

The predominance of wetlands in the flood plain 

may not be accurately represented by the numbers 

presented in table 2 because field observations 

indicated a high percentage of the active flood 

plain consisted of herbaceous and forested 

wetlands, which appeared to be closely tied to the stream and 

shallow ground-water system (fig. 2).

Field Data Collection

Field data were collected between May 2005 and October 

2006 for the purpose of computing bankfull geometry and 

discharge. Because these computations are based on the 

relative elevation of the bankfull channel, data collection 

Table 2 Basin characteristics for streamflow-gaging stations surveyed during this study for development of regional curves 

for the Coastal Plain Physiographic Province in Virginia and Maryland. 

[mi2, square miles; ft, feet; NAVD88, North American Vertical Datum of 1988; in., inches]

Station name Station 

number

Drainage 

area

(mi2)

Area 

foresteda

(percent)

Area 

wetlandsa

(percent)

Mean basin 

elevationb

(ft NAVD88)

Mean 

annual 

precipitation 

(in.)

24-hour, 

2-year 

rainfallc

(in.)

Collins Run Tributary near Providence Forge, VA 02042710 0.28 88.9 1.7 108.2 43 3.13

Bailey Branch Tributary at Spring Grove, VA 02042250 .71 66.0 4.2 125.6 45 3.21

Mill Creek near Skipton, MD 01492550 4.6 13.6 2.0 52.0 43 3.02

Aylett Creek at Aylett, VA 01674700 6.17 75.8 1.9 124.9 43 2.96

Bush Mill Stream near Heathsville, VA 01661800 6.82 68.9 7.9 107.4 43 3.04

Reedy Creek near Dawn, VA 01674200 16.8 81.4 4.4 196.7 43 3.00

Cat Point Creek near Montross, VA 01668500 45.6 68.0 4.7 138.9 43 3.00

Choptank River near Greensboro, MD 01491000 113 50.6 5.4 57.0 43 3.00

a

 Percent forested and wetland areas from 2000 land cover dataset (Goetz and others, 2004).

b

 Mean basin elevation from U.S. Geological Survey National Elevation Dataset 30-m data (U.S. Geological Survey, 2001).

c

 Bonnin and others (2004).

Figure 2. A flood plain wetland at the Cat Point Creek study site in Virginia. View 

from the left bank of the cross section toward the water edge near large trees.

 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
was focused on identification and surveying of 

bankfull features. Before surveying, the field 

team walked a distance of at least 20 times the 

estimated bankfull width upstream or downstream 

from the streamflow-gaging station to identify 

potential morphological features representing 

bankfull stage. These bankfull features typically 

included:

the top of the bank (fig. 3), or

a prominent break in slope at an elevation 

lower than the top of the bank, or

the elevation of depositional features, such 

as a bench feature on the bank (fig. 4).

At most sites in this study, the top of the 

bank represented the top of the bankfull channel. 

The active flood plain often decreased in elevation as it sloped away from the active channel 

into flood plain wetlands. This indicated that 

sediment has been repeatedly deposited as the 

stage exceeded bankfull and energy dissipated on 

the flood plain. Breaks in slope at an elevation 

lower than the top of the bank and point bars 

(fig. 4) were the next most common features that 

indicated the bankfull channel. In Bailey Branch 

Tributary and Collins Run Tributary (table 1), the 

channel was slightly incised but appeared to be 

building a new bankfull channel with identifiable 

benches. The higher features in these basins were 

terraces, with lower bankfull features defining 

the bankfull channel. These two sites are the only 

sites located south of the James River; they have 

the smallest drainage areas in Virginia and the 

steepest slopes. They were included in the dataset 

partly because they represent channel forms that 

were not present in more northern parts of the 

study area. The consistency of these benches 

throughout the surveyed sites indicates that the 

streams met the selection criteria for inclusion in 

the study. 

Surveys of the Bankfull Channel

At each site, a longitudinal profile of the 

study reach and two cross-section surveys at 

selected riffles within the reach were completed 

following procedures described by Harrelson and others 

(1994), Leopold (1994), and Rosgen (1996). By definition, 

streams that have bed material in the size range of 2 millimeters (mm) to 256 mm develop the characteristic riffle-pool 

sequences (Knighton, 1998) that are common in the streams 

in other physiographic provinces in Virginia and Maryland. 

The streams in the Coastal Plain observed during this study 

had varied bed material, usually dominated by sand (0.125 

•

•

•

mm to 2 mm). Often the bed material was heterogeneous, 

with gravel as large as 90 mm in size. It has been noted that 

concentrations of coarse particles analogous to riffles and 

spaced at five to seven times the channel width can be found 

in sand-bed streams (Leopold and others, 1966). Throughout 

the field surveys, streams were evaluated under the premise 

that pool-riffle sequences could be present. In the sand-bed 

streams, the shallowing of the thalweg and coarsening of the 

bed material were used to indicate the location of a riffle. This 

Figure 3. Bankfull features representing the top of the bank at Mill Creek in 

Maryland. Survey rod base is at the top of the bankfull feature.

Figure 4. Bankfull bench or point bar along the right bank of Cat Point Creek in 

Virginia. Flow is from right to left.

Development of Coastal Plain Bankfull Regional Curves   
methodology was used to keep the selection criteria consistent 

for all streams. 

The longitudinal profile consisted of an elevation profile 

of bankfull indicators, thalweg, and current water surface 

along the study reach, which extended at least 20 bankfull 

widths. The study reach also included the location of the 

streamflow-gaging station. If more than one possible bankfull 

feature was consistent throughout the reach, all features were 

surveyed but only one was ultimately selected as the bankfull 

feature. At stations along the longitudinal profile where 

bankfull features were not well defined, only water surface 

and thalweg were surveyed. Cross-section surveys were 

completed at two riffles within the study reach for computation of bankfull area, width, mean depth, and discharge. The 

elevation of the bankfull feature selected at each cross section 

was graphically compared to the longitudinal elevation profile 

of the bankfull channel to ensure that the two were similar. 

The longitudinal profile of the bankfull channel and 

cross sections were surveyed using a laser level and a 2–3 

person field crew. All surveys were referenced to a previously 

established datum at each streamflow-gaging station. Laser 

levels provide vertical elevation information but do not provide 

horizontal coordinates. For the longitudinal profile, horizontal 

stationing was determined with a measuring tape placed along 

one edge of the stream. For the cross sections, a tape was 

secured on the left bank and strung across to the right bank for 

stationing. The average of the channel geometry parameters 

from the two cross-section surveys was used in the regression 

analysis to develop regional curves. 

Pebble Counts

Pebble counts were conducted at the two riffle cross 

sections, following a modified Wolman (1954) methodology 

to document the particle-size distributions. Pebbles were 

selected by extending a finger into the water without looking 

and picking up the first particle touched (first blind touch). 

Particles were collected within the bankfull channel at regular 

intervals from bankfull to bankfull, including some bank 

particles, until a count of 100 was reached. The intermediate 

diameter (Wolman, 1954) of particles larger than 2 mm was 

measured with a ruler to the nearest millimeter. Particles 

smaller than 2 mm were compared with a sand gauge card for 

size classification. The diameter of each particle was recorded 

and grouped by sieve-size classes (comparable to using a 

square sieve to sort the material) based on the Wentworth 

scale (Leopold and others, 2000; Bunte and Abt, 2001). The 

sieve-size class for a particle of 15 mm would be represented 

as 16 mm, indicating that the particle is smaller than 16 mm 

but larger than 11 mm. The diameter of the median particle 

(D50) (Leopold and others, 1964) was calculated by ranking all 

records for particle sizes and selecting the 50th percentile. The 

particle size that is two standard deviations higher is the D84

or the particle size that is larger than 84 percent of the sample 

(Leopold and others, 1964). The data from both cross sections 

were combined to determine the D50 and D84 representative of 

riffles within the reach. 

Bankfull Discharge

For this study, bankfull discharge is defined as the flow 

that represents, or is a surrogate for, the range of flows that 

form the bankfull channel (Emmett, 2004). Even though 

larger flows may move appreciably more sediment during a 

given event, the bankfull discharge is expected to move the 

most sediment in a stream over time, thereby maintaining the 

flood plain, building point bars and meanders, and shaping 

the channel (Dunne and Leopold, 1978). This characterization 

of bankfull discharge has also been referred to as effective 

discharge—the discharge that transports the largest fraction of 

annual-sediment yield over a period of years (Andrews, 1980). 

Even though the similarity of these terms is debatable (Pickup 

and Warner, 1975), many have concluded that the bankfull 

discharge reasonably represents the effective discharge 

(Wolman and Miller, 1960; Andrews, 1980; Rosgen, 1996) 

and is an adequate surrogate for the range of flows that form a 

channel in streams that do not have very resistant boundaries 

(Knighton, 1998).

The recurrence frequency for bankfull discharge has also 

been a source of debate. Some investigators have suggested 

there is no common recurrence frequency (Williams, 1978), 

but the majority have indicated bankfull discharge can be 

expected over a relatively narrow range of recurrence intervals. 

For example, Rosgen (1996) indicates bankfull discharge 

occurs approximately every 1 to 2 years, and Wolman and 

Miller (1960) define the recurrence frequency even more 

narrowly as approximately every 1.5 years. Data-collection 

methods developed in the mid-1990s for natural-channel 

design assumed that bankfull discharge has a recurrence frequency of less than 2 years (Harrelson and others, 1994). More 

recently, bankfull discharge was assumed to have a recurrence 

frequency of 1 to 3 years for regional curve development in 

New York (Powell and others, 2004; Westergard and others, 

2005) and 1 to 2 years for regional curve development in 

Pennsylvania (White, 2001; Cinotto, 2003; Chaplin, 2005) 

and parts of Maryland, Virginia, and West Virginia (Keaton 

and others, 2005). The assumptions for this study generally 

are consistent with previous work of similar nature. The 

recurrence frequency of bankfull discharge was expected to be 

between 1 to 2 years, but bankfull features corresponding to 

discharges outside of this range were considered. 

Procedures described by Harrelson and others (1994), 

Rosgen (1996), and Powell and others (2004) were followed 

for identification of the bankfull channel and subsequent 

determination of bankfull discharge. These procedures are 

consistent with those used by Keaton and others (2005) in the 

Valley and Ridge Physiographic Province of Virginia. Longterm streamflow and cross-sectional geometry data stored by 

the USGS in the Automated Data Processing System (ADAPS; 

U.S. Geological Survey, 2003) were used in combination with 

   Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
bankfull indicators identified in the field to define the bankfull 

channel at each site. 

After the bankfull channel was defined along the reach 

including the streamflow-gaging station, the water-surface 

elevation (stage) that would occur in the bankfull channel 

and a relation between stage and discharge (rating) were used 

to select the discharge that corresponded to the elevation of 

the bankfull channel at the streamflow-gaging station. The 

recurrence frequency of the bankfull discharge was then 

determined by comparing the bankfull discharge to a frequency distribution of annual peak discharges fit to a Pearson 

Type III frequency distribution (Hydrology Subcommittee of 

the Interagency Advisory Committee on Water Data, 1982). 

Comparison Surveys of Maryland Sites

Two sites were selected for duplicate surveys to establish 

whether the surveying techniques used in this study produced 

results similar to surveys conducted for the Maryland Coastal 

Plain regional curves (McCandless, 2003). One site with a 

large drainage area, Choptank River near Greensboro, MD 

(113 mi2), and one site with a small drainage area, Mill Creek 

near Skipton, MD (4.6 mi2), were selected for duplicate 

surveys to compare channel geometry at both ends of the 

range of drainage areas. The duplicate surveys were conducted 

to ensure that the variability observed was not due to differing 

survey techniques. The methods described in this report were 

used to survey both Maryland sites. Cross sections were 

selected on the basis of field personnel judgment and not 

necessarily at the exact same location as McCandless (2003). 

The resulting channel geometry measurements indicate that 

the surveying techniques used in this study produced similar 

results (table 3). 

Bankfull width and mean depth can be highly variable, 

but their product, cross-sectional area, tends to be a more 

consistent characteristic. For Choptank River, the largest 

site included in this investigation, there was a 0.2-percent 

difference in cross-sectional area between the McCandless 

(2003) survey and that conducted in this study (table 3). For 

Mill Creek there was a 12.2-percent difference in the crosssectional area between the McCandless (2003) survey and that 

conducted in this study (table 3). Streams with large basins 

tend to have less variability in cross-sectional channel geometry than streams with small basins, so it was not surprising 

that the difference between Mill Creek surveys was larger. 

Bankfull width and mean depth measurements were more variable than cross-sectional area for the duplicate surveys. For the 

Choptank River, the bankfull width differed by 19.2 percent, 

and mean depth differed by 16.6 percent. For Mill Creek, 

the bankfull width differed by 26.3 percent, and mean depth 

by 18.8 percent. The McCandless (2003) cross section 

locations for Mill Creek appear to be 400 ft downstream from 

those surveyed for this study, and there were some wetland 

drainages in between the cross sections, which may account 

for the differences in width and depth. In addition to the 

duplicate field surveys, an analysis of covariance test between 

the McCandless (2003) data and that of this study showed 

no significant difference in the slope or intercepts for either 

regression. The test and results are described in the section 

comparing the Coastal Plain Regressions for Maryland, North 

Carolina, and Virginia. The McCandless (2003) data and the 

six sites surveyed during this study were combined into one 

dataset for the development of one set of regional curves for 

the Coastal Plain in Virginia and Maryland. 

Analysis of Bankfull Channel Data

Bankfull features from the longitudinal profile surveys 

that were relatively consistent throughout the reach, nearly 

parallel to the water-surface slope, and were located at a 

reasonable elevation based on the 1- to 2-year recurrence 

interval range were used to define the bankfull channel 

throughout the reach. Only bankfull features that met these 

criteria were retained in the final longitudinal profile plots 

(appendix 1). Bankfull elevations from the two cross-section 

surveys were plotted with the longitudinal profiles and served 

as an additional check that bankfull was appropriately defined. 

The longitudinal profiles and cross-section bankfull 

elevations were used to select the bankfull stage at the 

streamflow-gaging station. A trend line through the longitudinal profile bankfull features was extended through the location 

of the streamflow-gaging station. The elevation where the 

trend line crossed the location of the streamflow-gaging station represents bankfull stage. Bankfull discharge (table 4) was 

determined by comparing this bankfull stage to ratings available for each site. The ratings relate stage to discharge over a 

range of hydrologic conditions, including bankfull discharge. 

Table 3. Duplicate-survey results from stream bankfull channel 

geometry surveys at two streamflow-gaging stations

in Maryland.

[USGS, U.S. Geological Survey; na, not applicable]

McCandless

(2003)

USGS

(This study)

Percent 

difference 

Choptank River near Greensboro, Maryland (01491000)

Bankfull area, in square feet 383.0 382.5 0.2

Bankfull width, in feet 97.2 115.9 -19.2

Bankfull mean depth, in feet 3.9 3.3 16.6

Width-to-depth ratio 24.7 35.5 -43.9

Rosgen stream typea C5c C na

Mill Creek near Skipton, Maryland (01492550)

Bankfull area, in square feet 27.1 23.8 12.2

Bankfull width, in feet 26.8 19.8 26.3

Bankfull mean depth, in feet 1.0 1.2 -18.8

Width-to-depth ratio 26.5 16.2 38.9

Rosgen stream typea C5 C na

a

 From Rosgen (1996).

Development of Coastal Plain Bankfull Regional Curves 
Table 4. Bankfull channel geometry data collected for this study in streams in the Coastal Plain Physiographic Province in Virginia and Maryland.

[Values in the table represent the average of two cross sections for each site. mi2, square miles; ft2, square feet; ft, feet; ft3/s, cubic feet per second; mm, millimeters; >, greater than; <, less than]

Station name Station number Drainage area (mi2

)

Crosssectional 

area (ft2

)

Width 

(ft)

Mean 

depth 

(ft)

Estimated 

discharge 

(ft3/s)

Recurrence 

interval 

(years)

1.5-year 

discharge 

(ft3/s)

D50

a

(mm)

D84

b

(mm)

Width:

depth 

ratio

Entrenchment

ratio

Channel 

slope 

(ft/ft)

Rosgen 

stream 

typec

Collins Run Tributary near Providence Forge, VA 02042710 0.28 6.2 7.7 0.8 19.5 1.5 20.2 2 8 9.8 2.7 0.0049

E

Bailey Branch Tributary at Spring Grove, VA 02042250 .71 13.4 10.3 1.3 48.0 2.1 30.0 11 32 7.6 2.7 .0039

E

Mill Creek near Skipton, MD 01492550 4.6 23.8 19.8 1.2 30.1 1.0 90.6 .5 2 16.2 > 4.6* .0017

C

Aylett Creek at Aylett, VA 01674700 6.17 30.8 16.6 1.9 170.0 1.3 198.4 4 8 8.9 > 6.3* .0015

E

Bush Mill Stream near Heathsville, VA 01661800 6.82 58.3 23.3 2.5 49.8 < 1 year 127.0 .5 2 9.3 > 4.2* .0025

E

Reedy Creek near Dawn, VA 01674200 16.8 50.5 25.9 2.0 116.0 1.1 144.3 .25 2 13.3 > 4.5* .0038

C

Cat Point Creek near Montross, VA 01668500 45.6 97.0 31.3 3.1 109.6 < 1 year 476.4 1 2 10.4 > 10.2* .0025

E

Choptank River near Greensboro, MD 01491000 113 382.5 115.9 3.3 636.6 1.1 1450.0 11 23 35.5 > 2.2* .0002

C

a Particle size larger than 50 percent of cross section streambed material, or median particle size; value represents the sieve size a particle would not pass through.b Particle size larger than 84 percent of cross section streambed material.c From Rosgen (1996). This classification system is not applicable for all Coastal Plain streams. Numerical designation for particle size was not assigned because pebble counts were only conducted at 

riffles.

 * The flood-prone elevation was not surveyed because the flood-plain elevation was lower than two times bankfull elevation for more than 60 feet in either direction from the channel.

10 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
The recurrence interval (table 4) of each bankfull discharge 

was determined from a frequency distribution of annual peak 

discharges following methods described by the Hydrology 

Subcommittee of the Interagency Advisory Committee on 

Water Data (1982). All but two sites had recurrence intervals 

between 1 and 2 years. Cat Point Creek, VA, and Bush Mill 

Stream, VA, had recurrence intervals less than 1 year. Both 

sites are in the Northern Neck, have sand-bed channels, and 

have high percentages of wetlands in the basin. Only one site 

had a recurrence interval greater than 1.5 years. Coastal Plain 

basins may have large percentages of wetland storage, which 

may contribute to low bankfull-discharge recurrence intervals. 

The slope of the reach from one riffle thalweg elevation to a 

downstream riffle thalweg elevation was calculated for each 

site (table 4; Leopold and others, 1964). 

Two cross-section profiles for each site were plotted 

showing the water-surface elevation at the time of the survey 

and the bankfull stage (appendix 1). Bankfull cross-sectional 

area, bankfull width, and bankfull mean depth for each riffle 

were determined from field data, along with the D50- and D84-

particle size for the two riffles combined (table 4; appendix 1). 

Additional ratios were calculated from the cross-section 

geometry data (table 4): width-to-depth ratio (bankfull width 

divided by mean depth) and entrenchment ratio (flood-prone 

width divided by bankfull width). The flood-prone width 

represents the elevation on the flood plain that equals the 

elevation of two times the deepest point of the bankfull cross 

section (Rosgen, 1996). The entrenchment ratio provides a 

reference to how steep and wide the flood plain is relative to 

the bankfull width. The width-to-depth ratio and entrenchment 

ratio values in table 4 were calculated as the average of the 

two cross sections for each site. 

Comparison of Coastal Plain Regressions for 

Maryland, North Carolina, and Virginia Stations 

More than 15 sets of regional curves have been developed 

for physiographic provinces in the Eastern United States 

(Natural Resources Conservation Service, 2007). Dunne and 

Leopold (1978) found consistent patterns in channel geometry 

within this portion of the United States. The availability of 

data for the Coastal Plain in Virginia and the two adjacent 

states of Maryland and North Carolina provides an opportunity 

to examine regional patterns within one physiographic 

province. There are three questions to consider: 

Are the datasets from Virginia, Maryland, and North 

Carolina significantly different from each other? 

Are the site-selection criteria and survey methodologies 

similar for each state? 

Could the datasets be combined to create one set of 

Coastal Plain regional curves that explain more variability than the regional curves for any one state? 

•

•

•

The first question was addressed through statistical 

examination of the slopes and intercepts of channel geometry 

regressions for each state. Individual regressions for Virginia 

(n = 6), Maryland (n = 14; McCandless, 2003), and North 

Carolina stations (n = 16; Doll and others, 2003) were plotted 

together for comparison (figs. 5, 6, 7, and 8). An analysis of 

covariance (ANCOVA) was performed to determine if there 

were significant differences in slopes or intercepts between the 

regressions plotted in figures 5–8. Within the statistical package, MATLAB (The MathWorks, Inc., 2006), the ‘aoctool’ 

function was used to perform the ANCOVA and calculate the 

simple linear regressions for three groups—Virginia, 

Maryland, and North Carolina. A multiple comparison 

procedure was used to compare regressions of each group 

(Virginia and Maryland, Maryland and North Carolina, North 

Carolina and Virginia) and to determine whether pairs of 

slopes or intercepts were significantly different based on a 

specified alpha level (alpha = 0.05). 

The compare procedure subtracts the Virginia slope 

from the Maryland slope to examine the overlap in the slopes 

of each pair of regressions. The same is done for paired 

regression intercepts. The range of overlap is described by 

a 95-percent confidence interval for the difference in values 

(The MathWorks, Inc., 2006). If the confidence interval 

includes zero, there is enough overlap in the slope or intercept 

values of the two regressions that they cannot be considered 

significantly different (The MathWorks, Inc., 2006). 

The slopes and intercepts for each regression model were 

paired with those of another state, with all combinations examined as part of the ANCOVA procedure. The results of this 

analysis indicated no differences in the slopes or intercepts for 

the regressions of drainage area and bankfull cross-sectional 

area, bankfull width, or bankfull mean depth at the 95-percent 

significance level (all confidence intervals contained zero). 

However, the results of the analysis of the regressions of 

drainage area and bankfull discharge indicated a significant 

difference in the slopes of Virginia and Maryland, and Virginia 

and North Carolina. In the Maryland Coastal Plain regional 

curves study, the bankfull discharge was significantly higher 

for sites on the west side of the Chesapeake Bay than on the 

east side (McCandless, 2003). This was attributed to differences in channel slope in the basins studied. To test whether 

western sites (which commonly have steeper slopes (McCandless, 2003)) would show a similar distribution, the Virginia 

regression was compared with a regression of only Maryland 

western sites, but the results still showed a significant difference between the slopes of the regressions. By including 

only western sites from the Maryland dataset, the regression 

contained four sites with large drainage areas and only one site 

with a small drainage area, increasing the potential that the site 

with a small drainage area could disproportionately influence 

the regression slope. The Virginia regression contained six 

sites with mid-range drainage areas. 

Development of Coastal Plain Bankfull Regional Curves 11
Figure 6. Log-log plot of three regressions of bankfull width (W) and drainage area (DA) for streams 

in the Coastal Plain Physiographic Province in Maryland, Virginia, and North Carolina.

12  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland

Figure 5. Log-log plot of three regressions of bankfull cross-sectional area (CSA) and drainage area (DA) for 

streams in the Coastal Plain Physiographic Province in Maryland, Virginia, and North Carolina.

0.1 1 10 100 1,000

1

10

100

1,000

DRAINAGE AREA, IN SQUARE MILES

BANKFULL AREA, IN SQUARE FEET

Figure 5. Log-log plot of three regressions of bankfull cross-sectional area (CSA) and drainage area (DA) for 

streams in the Coastal Plain Physiographic Province in Maryland, Virginia, and North Carolina. 

EXPLANATION

Regression data point, line style, and equation of regression line

Maryland CSA = 10.358 (DA) 0.698

Virginia CSA = 12.843 (DA) 0.607

North Carolina CSA = 14.330 (DA) 0.657

0.1 1 10 100 1,000

1

10

100

1,000

DRAINAGE AREA, IN SQUARE MILES

BANKFULL WIDTH, IN FEET

Figure 6. Log-log plot of three regressions of bankfull width (W) and drainage area (DA) for streams in the Coastal 

Plain Physiographic Province in Maryland, Virginia, and North Carolina. 

Maryland W = 10.304 (DA) 0.381

Virginia W = 10.777 (DA) 0.383

North Carolina W = 10.967 (DA) 0.363

EXPLANATION

Regression data point, line style, and equation of regression line
Figure 7. Log-log plot of three regressions of bankfull mean depth (D) and drainage area (DA) for 

streams in the Coastal Plain Physiographic Province in Maryland, Virginia, and North Carolina.

Figure 8. Log-log plot of three regressions of estimated bankfull discharge (Q) and drainage 

area (DA) for streams in the Coastal Plain Physiographic Province in Maryland, Virginia, and North 

Carolina.

Development of Coastal Plain Bankfull Regional Curves 13

0.1 1 10 100 1,000

DRAINAGE AREA, IN SQUARE MILES

Figure 7. Log-log plot of three regressions of bankfull mean depth (D) and drainage area (DA) for streams in 

the Coastal Plain Physiographic Province in Maryland, Virginia, and North Carolina. 

0.1

1

10

100

BANKFULL MEAN DEPTH, IN FEET

Maryland D = 1.008 (DA) 0.317

Virginia D = 1.184 (DA) 0.227

North Carolina D = 1.289 (DA) 0.296

EXPLANATION

Regression data point, line style, and equation of regression line

0.1 1 10 100 1,000

1

10

100

1,000

DRAINAGE AREA, IN SQUARE MILES

BANKFULL DISCHARGE, IN CUBIC FEET PER SECOND

Figure 8. Log-log plot of three regressions of estimated bankfull discharge (Q) and drainage area (DA) for 

streams in the Coastal Plain Physiographic Province in Maryland, Virginia, and North Carolina. 

Maryland Q = 19.655 (DA) 0.742

Virginia Q = 34.413 (DA) 0.459

North Carolina Q = 18.281 (DA) 0.704

EXPLANATION

Regression data point, line style, and equation of regression line
The site-selection criteria and the survey methodologies 

were evaluated for Maryland and North Carolina studies. 

The Maryland data (McCandless, 2003; table 5) represent 

channel geometry from published surveys of sites where 

USGS streamflow-gaging stations are located. The site-selection process for inclusion in the Maryland regional curves 

was similar to that of this study. Survey results published in 

McCandless (2003) were verified during this investigation 

with two duplicate surveys (table 3). The North Carolina data 

(Doll and others, 2003) represent channel geometry from an 

on-line draft report and include nine reference reaches that are 

not located at USGS streamflow-gaging stations. Only seven 

of the North Carolina sites surveyed were located at USGS 

streamflow-gaging stations. While reference sites are useful 

in stream restoration design, they lack the historical data to 

verify the discharge relation and recurrence interval that a long 

period of record at a USGS streamflow-gaging station affords. 

North Carolina survey results were not verified through 

duplicate surveys during this investigation because this was 

outside the scope of work. The North Carolina cross-section 

surveys were conducted at both riffles and runs, whereas the 

Virginia and Maryland cross-section surveys were conducted 

only at riffles. 

The source of variability in bankfull geometries is an 

important consideration in the decision to include or omit 

data. Variability due to natural channel-forming processes can 

largely be explained by drainage area (Leopold, 1994; Rosgen, 

1996). However, variability resulting from different siteselection criteria or methods cannot be explained by drainage 

area and may lead to spurious relations. The similarity of the 

site-selection criteria for this study and McCandless (2003), 

along with relatively good agreement between duplicate surveys, supports the combination of these two datasets into one 

composite dataset. Because survey results presented in Doll 

and others (2003) were not verified through duplicate surveys 

and some sites were not at USGS streamflow-gaging stations, 

further study would be necessary to support inclusion of the 

North Carolina data. For this study, only the data collected 

at the 20 sites in Maryland and Virginia were considered for 

regional curve development.

The third question was addressed by comparing the 

regression statistics for sites surveyed for this study and a 

combined dataset of sites surveyed for this study and sites 

surveyed by McCandless (2003). The regression statistics for 

regional curves developed with data from this study (n = 8) 

compared with regional curves developed with the combined 

data from both studies (n = 20) indicate that the regression 

was strengthened with the addition of McCandless (2003) 

data. The amount of variability in bankfull geometry or 

discharge that is explained by drainage area is measured with 

the coefficient of determination (R2). With the addition of 

McCandless (2003) data to the regression, the R2 statistic for 

cross-sectional area increased from 0.925 to 0.945, indicating 

that drainage area explains 2 percent more of the variability. 

It is expected that the residual standard error (SE) would 

decrease as the predictive power of a regression increases. 

Table 5. Bankfull channel geometry data collected by McCandless (2003) in streams in the Coastal Plain 

Physiographic Province in Maryland and Delaware.

[mi2, square miles; ft2, square feet; ft, feet; ft3/s, cubic feet per second; mm, millimeters]

Station name Station 

number

Drainage 

area

(mi2)

Crosssectional 

areaa (ft2)

Width 

(ft)

Mean 

depth 

(ft)

Estimated 

discharge 

(ft3/s)

Recurrence 

interval 

(years)

Rosgen 

stream 

typeb

Glebe Branch at Valley Lee, MD 01661430 0.3 5.3 7.4 0.7 11.9 1.1 C4

Beaverdam Branch at Houston, DE 01484100 2.8 20.9 14.7 1.4 35.0 1.4 E5

Mill Creek near Skipton, MD 01492550 4.6 27.1 26.8 1.0 39.1 1.1 C5

Faulkner Branch at Federalsburg, MD 01489000 7.1 31.6 17.6 1.8 85.9 1.2 E5

Sallie Harris Creek near Carmichael, MD 01492500 8.1 51.3 17.4 3.0 78.0 1.1 E5

Gravel Run at Beulah, MD 01492050 8.4 33.5 17.9 1.9 64.7 1.4 E5

Murderkill River near Felton, DE 01484000 13.6 76.7 33.5 2.3 100.0 1.1 C5cSt. Clements Creek near Clements, MD 01661050 18.5 92.1 30.1 3.1 273.4 1.2 E5

St. Mary’s River at Great Mills, MD 01661500 24 121.4 38.8 3.1 464.9 1.2 C4

Nassawango Creek near Snow Hill, MD 01485500 44.9 111.4 36.4 3.1 221.6 1.1 E5

Mattawoman Creek near Pomonkey, MD 01658000 54.8 119.1 37.0 3.2 540.0 1.2 C4

Nanticoke River near Bridgeville, DE 01487000 75.4 213.0 53.8 4.0 340.7 1.2 C5cWestern Branch at Upper Marlboro, MD 01594526 89.7 271.0 56.7 4.8 673.2 1.0 C5cChoptank River near Greensboro, MD 01491000 113 383.0 97.2 3.9 689.3 1.1 C5ca

 Values updated to represent the product of width and depth, and rounded to one decimal place.

b

 From Rosgen (1996).

14  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
With the addition of the McCandless (2003) data, the SE for 

cross-sectional area decreased from 0.372 to 0.279. Prediction intervals around the regression of the combined dataset 

were 33 percent narrower than prediction intervals around 

the regression of data from this study alone. Increases in R2

statistic and the decreases in SE were of similar magnitude for 

bankfull width, mean depth, and estimated bankfull discharge 

as those presented for cross-sectional area. These evaluations 

support the combination of sites surveyed for this study and 

sites surveyed by McCandless (2003; n = 20) into a composite 

dataset for the creation of one set of regional curves for the 

Coastal Plain. 

Coastal Plain Regional Curves

Simple linear regression techniques were used to develop 

regional curves for the Coastal Plain in Virginia and Maryland 

from two sources of data: (1) channel geometry data from 

8 sites that were surveyed for this study in the Coastal Plain 

of Virginia and the Delmarva Peninsula of Maryland (table 4), 

and (2) the remaining 12 sites surveyed by McCandless (2003) 

that were not duplicated in this study (table 5) for a total of 

20 sites in the regression analysis. MATLAB version 7.3.0.267 

(R2006b) software (The MathWorks, Inc., 2006) was used for 

the statistical analyses and graphics. 

The response variables—bankfull cross-sectional area, 

bankfull width, and bankfull mean depth and estimated bankfull discharge for all 20 sites (tables 4 and 5)—were regressed 

against the explanatory variable—drainage area—to show the 

relation between drainage area and each of the variables. The 

relation between drainage area and each response variable 

was described by fitting a power function with a best-fit 

line through the data points for each parameter using the 

least-squares method. The power functions were plotted on a 

log-log scale. The resulting power functions commonly have 

the form: y = a(DA)b. For the purpose of computing diagnostic 

statistics, the power functions were transformed to a log-linear 

form: 

where 

ln = natural log, base e, 

y = bankfull response variable,

DA = drainage area,

a = the intercept of the regression line, and 

b = a coefficient of the regression line 

representing the slope of the regression 

line. 

The power functions that relate bankfull cross-sectional 

area, width, mean depth, and estimated bankfull discharge 

to drainage area representing the Coastal Plain of Virginia 

and Maryland are illustrated in figures 9, 10, 11, and 12. 

Table 6 gives the equations and diagnostic statistics for each 

regression. These regional curves also show the 95-percent 

prediction intervals for individual estimates of the response 

variable. Prediction intervals represent a 95-percent certainty 

that an individual observed value of y for a given x will fall 

within the upper and lower limits of the interval (Helsel and 

Hirsch, 2002, p. 242–245; Keaton and others 2005).

Regional curves (and other regression relations) are 

only estimates of the true relation between bankfull response 

variables and drainage area because they are generated from 

a sample of sites that is intended to represent the population. 

The applicability of regional curves depends on how well the 

sample of sites represents the population, adherence to the 

assumptions of the underlying regression model, the fit of the 

(1)

Development of Coastal Plain Bankfull Regional Curves 15

Table 6. Equations and diagnostic statistics for regional curves relating drainage area to bankfull discharge and 

bankfull channel geometry for streams in the Coastal Plain Physiographic Province in Virginia and Maryland.

[R2, correlation coefficient; n, number of data points; CSA, bankfull cross-sectional area; DA, drainage area; W, bankfull width; D, bankfull 

mean depth; Q, estimated bankfull discharge]

Equation R2

Residual 

standard error 

(natural log 

base e)

Residual 

standard error 

(percent)a n

p-value for 

regression 

slopeb

F-statistic F-statistic 

p-valuec

p-value 

for 

Lillietestd

CSA = 11.9899*(DA)0.63803 0.945 0.279 28.6 20 <0.0001 306.39 < 0.0001 0.137

W = 10.4459*(DA)0.36543 .890 .232 23.1 20 < .0001 145.93 < .0001 .386

D = 1.145*(DA)0.27345 .871 .190 18.1 20 < .0001 121.80 < .0001 .116

Q = 28.3076*(DA)0.59834 .793 .552 59.3 20 < .0001 68.87 < .0001 .307

a

 Conversion from residual standard error natural log to percent, following Tasker (1978).

b

 p-value less than 0.05 means that the slope of the regression is different than zero.

c

 p-value of the F-statistic presented although assumption of log-normal distribution is not met.

d

 Lillietest (The MathWorks Inc., 2006) performs a Lillilifors test of the default null hypothesis that the sample in vector x comes

from a distribution in the normal family, against the alternative that it does not come from a normal distribution. A p-value of greater

than 0.05 indicates that the regression residuals are normally distributed.

ln( ) y a = + ln( ) ( l b D * n( A))
Figure 10. Regional curve relating bankfull width (W) to drainage area (DA) for streams in the non-urban, non-tidal Coastal 

Plain Physiographic Province of Virginia and Maryland.

16  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland

0.1 1 10 100 1,000

1

10

100

1,000

DRAINAGE AREA, IN SQUARE MILES

BANKFULL WIDTH, IN FEET

Figure 10. Regional curve relating bankfull width (W) to drainage area (DA) for streams in the non-urban, 

non-tidal Coastal Plain Physiographic Province of Virginia and Maryland.

W = 10.4459*(DA) 0.36543

95-percent prediction interval

Figure 9. Regional curve relating bankfull cross-sectional area (CSA) to drainage area (DA) for streams in the non-urban, 

non-tidal Coastal Plain Physiographic Province of Virginia and Maryland.

0.1 1 10 100 1,000

1

10

100

1,000

DRAINAGE AREA, IN SQUARE MILES

BANKFULL CROSS-SECTIONAL AREA, IN SQUARE FEET

Figure 9. Regional curve relating bankfull cross-sectional area (CSA) to drainage area (DA) for streams in the 

non-urban, non-tidal Coastal Plain Physiographic Province of Virginia and Maryland.

CSA = 11.9899*(DA) 0.63803

95-percent prediction interval
Figure 11. Regional curve relating bankfull mean depth (D) to drainage area (DA) for streams in the non-urban, non-tidal 

Coastal Plain Physiographic Province of Virginia and Maryland.

Figure 12. Regional curve relating estimated bankfull discharge (Q) to drainage area (DA) for streams in the non-urban, 

non-tidal Coastal Plain Physiographic Province of Virginia and Maryland.

Development of Coastal Plain Bankfull Regional Curves 17

0.1 1 10 100 1,000

0.1

1

10

DRAINAGE AREA, IN SQUARE MILES

BANKFULL MEAN DEPTH, IN FEET

Figure 11. Regional curve relating bankfull mean depth (D) to drainage area (DA) for streams in the non-urban, 

non-tidal Coastal Plain Physiographic Province of Virginia and Maryland.

D = 1.145*(DA) 0.27345

95-percent prediction interval

0.1 1 10 100 1,000

1

10

100

1,000

DRAINAGE AREA, IN SQUARE MILES

BANKFULL DISCHARGE, IN CUBIC FEET PER SECOND

Figure 12. Regional curve relating estimated bankfull discharge (Q) to drainage area (DA) for streams in the 

non-urban, non-tidal Coastal Plain Physiographic Province of Virginia and Maryland.

Q = 28.3076*(DA) 0.59834

95-percent prediction interval
curve used to develop it, influence of any given data point, and 

the confidence in the relation over the range of represented 

drainage areas. The applicability of regional curves developed 

here was evaluated on the basis of selected statistical diagnostics that measure the significance of the slope (indicated 

by p-values), the distribution of residuals, influence of each 

streamflow-gaging station (given by statistical measures of 

Cook’s distance and two leverage statistics: hi and standardized residual), and the amount of variability explained by 

drainage area (given by R2). For this study the slope of each 

regional curve was considered significantly different from zero 

if the p-value (probability that a difference occurs by chance) 

was less than 0.05. 

The regressions developed have slopes that are significantly different from zero (p-values are less than 0.0001; 

table 6) with residuals that upon visual inspection appear to 

be normally distributed and to vary randomly with drainage 

area (figs. 13, 14, 15, and 16). Higher R2 values suggest that 

a greater portion of the variability is explained but are not 

necessarily indicative of a better regression relation. The R2

value indicates that 94.5 percent of the variability in bankfull 

cross-sectional area is explained by drainage area, with 

89.0 percent, 87.1 percent, and 79.3 percent of the variability 

explained by drainage area for bankfull width, mean depth, 

and bankfull discharge, respectively (table 6). The relatively 

high R2 value for cross-sectional area indicates that it has the 

strongest relation to drainage area of the parameters measured. 

Lower R2 values for bankfull width and mean depth indicate 

the greater variability in the geometries measured. 

Width and depth may vary considerably from site to 

site due to differences in local morphology; however, they 

generally vary in opposite directions. Their product—crosssectional area—tends to be a more consistent characteristic 

and to maintain a higher correlation with drainage area. The 

lower R2 values for estimated bankfull discharge may reflect 

the time period for which streamflow data were available and 

the age of the rating tables for the streamflow-gaging stations. 

The variance in bankfull discharge also may be related to 

basin characteristics and geographic location. 

18 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland

Figure 13. (A) Regression residuals for regional curves relating 

drainage area to bankfull cross-sectional area (for data, see fig. 9) 

and (B) box plot of the distribution of residuals for bankfull crosssectional area.

Figure 14. (A) Regression residuals for regional curves relating 

drainage area to bankfull width (for data, see fig. 10) and (B) box 

plot of the distribution of residuals for bankfull width.

10-1 100 101 102 103

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

REGRESSION RESIDUALS FOR BANKFULL AREA

DRAINAGE AREA, IN SQUARE MILES

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

(A)

(B)

EXPLANATION

75th percentile

25th percentile

50th percentile

Outlier

Percentile—Percentage of

values equal to or less than

indicated values

REGRESSION RESIDUALS FOR BANKFULL AREA

Data value less than or equal to 1.5 times

the interquartile range outside the quartile

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

(A)

(B)

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

10-1 100 101 102 103

DRAINAGE AREA, IN SQUARE MILES

REGRESSION RESIDUALS FOR BANKFULL WIDTH REGRESSION RESIDUALS FOR BANKFULL WIDTH

EXPLANATION

75th percentile

25th percentile

50th percentile

Outlier

Percentile—Percentage of

values equal to or less than

indicated values

Data value less than or equal to 1.5 times

the interquartile range outside the quartile
Each regression was evaluated closely to determine if 

any points represented outliers. The residuals were visually 

inspected to see if there was non-constant variance (heteroscedascity) as the explanatory variable increased (figs. 13–16). 

Box plots of the residuals showed their approximate normality 

with only one outlier for bankfull width. A lillietest (The 

MathWorks Inc., 2006), a version of Lillilifors test, was 

performed to test the normality of the residuals. All p-values 

were greater than 0.05, indicating that the regression residuals 

are normally distributed.

The Choptank River, MD, was an outlier for bankfull 

width, but it was not an outlier for any other parameter. The 

measured width was more that twice the width of any other 

site measured, which may be why it does not fit with the other 

values in the regression. Measures of hi (leverage in the xdirection), standardized residual (leverage in the y-direction), 

and Cook’s Distance statistic for all regressions were within 

the expected limits, indicating no individual streamflowgaging station had excessive influential effects on the regressions. 

Limitations

The bankfull regional curves presented in this report 

are applicable to the identification of bankfull geometry and 

discharge in non-tidal, non-urban streams of the Coastal Plain 

Physiographic Province. Factors, such as land use, stream 

gradient, stream type, mean elevation, and drainage area, 

should be considered when assessing the applicability of the 

Coastal Plain bankfull regional curves. The streams of the 

Coastal Plain often transition between swamps with no defined 

channel geometry to areas of slightly higher gradient with 

defined channel geometry. The predominance of flood plain 

wetlands and the extremely low gradients of the flood plains 

may prove to be important considerations in stream restoration 

projects. 

Streams included in this study had well-defined bankfull 

channel geometries that could be surveyed. Because of the 

site-selection requirements, many streams were excluded 

from the dataset. The streams that were included in this study 

are single-channel, low-gradient, meandering, riffle/pool 

Development of Coastal Plain Bankfull Regional Curves 19

Figure 15. (A) Regression residuals for regional curves relating 

drainage area to bankfull mean depth (for data, see fig. 11) and 

(B) box plot of the distribution of residuals for bankfull mean 

depth.

Figure 16. (A) Regression residuals for regional curves 

relating drainage area to estimated bankfull discharge (for data, 

see fig. 12) and (B) box plot of the distribution of residuals for 

estimated bankfull discharge.

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

10-1 100 101 102 103

REGRESSION RESIDUALS FOR

BANKFULL MEAN DEPTH

REGRESSION RESIDUALS FOR

BANKFULL MEAN DEPTH

DRAINAGE AREA, IN SQUARE MILES

(A)

(B)

EXPLANATION

75th percentile

25th percentile

50th percentile

Outlier

Percentile—Percentage of

values equal to or less than

indicated values

Data value less than or equal to 1.5 times

the interquartile range outside the quartile

-1.0

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1.0

-1.0

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

10-1 100 101 102 103

REGRESSION RESIDUALS FOR

BANKFULL DISCHARGE

REGRESSION RESIDUALS FOR

BANKFULL DISCHARGE

DRAINAGE AREA, IN SQUARE MILES

(A)

(B)

EXPLANATION

75th percentile

25th percentile

50th percentile

Outlier

Percentile—Percentage of

values equal to or less than

indicated values

Data value less than or equal to 1.5 times

the interquartile range outside the quartile
streams with channel slopes less than 0.005. The valleys that 

contain the streams are broad, with wide floodplains and some 

terraces. Based on the Rosgen (1994) classification of natural 

rivers, the stream types represented by the regional curves 

developed in this study could be classified as 55-percent 

stream type E and 45-percent stream type C. No other stream 

types were included in the investigation. While the regional 

curves represent both types of streams together, the applicability of the curves for identifying bankfull features on other 

types of channels has not been tested. Seventy-five percent 

of mean elevations for each basin were higher than the mean 

elevation of the Coastal Plain. The mean basin elevation is 

an additional consideration as to the applicability of these 

regional curves. 

Fifty percent of the stage-discharge ratings for 

streamflow-gaging stations were at least 25 years old. The 

recurrence intervals presented in this report are based on 

short-record discharge datasets. Many of the datasets contain 

only 10 years of peak-flow data, and can contain one peak 

that could represent an outlier. For this reason, the recurrence 

intervals calculated from the peak-flow dataset may be slightly 

lower than would be expected if a longer-record dataset were 

available. 

The streams surveyed were in close proximity to a USGS 

streamflow-gaging station, which often was mounted on a 

bridge or culvert. Because of manmade features within the 

study reaches, the streams do not represent ‘reference reach 

conditions’. No assessment of habitat health was conducted, 

and no statements were made regarding habitat conditions. 

The regional curves provide an estimate of bankfull geometry 

and serve as tools for field identification of bankfull features. 

They can be used in stream assessments of ungaged streams 

as a guide for identifying the expected natural-channel 

geometry in those streams. The regional curves are believed 

to be accurate within the prediction intervals for the range of 

drainage areas studied. Outside this range it is uncertain how 

far the regression relations may be extended with accuracy.

Summary

The U.S. Geological Survey (USGS), in cooperation 

with the Virginia Coastal Zone Management Program and the 

Virginia Department of Conservation and Recreation Coastal 

Nonpoint Source Pollution Control Program, developed 

bankfull regional curves for streams in non-urban, non-tidal 

coastal areas of Virginia in 2005. These regional curves are 

one-variable, ordinary least-squares regressions relating 

bankfull discharge, bankfull cross-sectional area, bankfull 

width, and bankfull mean depth to drainage area in settings 

that are expected to have homogenous runoff characteristics. 

Equations describing the regional curves can be used to 

estimate the discharge and geometry of the bankfull channel 

when the drainage area of the watershed is known. 

Bankfull geometry and discharge data were collected at 

six streamflow-gaging stations and associated stream reaches 

(sites) in Virginia and two sites on the Delmarva Peninsula of 

Maryland. Data from these 8 sites were combined with data 

from 12 sites in Maryland for the development of regional 

curves. All sites represent drainages that feed into the Chesapeake Bay. Drainage areas for the 20 sites range from 0.28 mi2

to 113 mi2. 

Field-data collection included one longitudinal profile of 

bankfull features and channel slope, two cross-section surveys 

of channel geometry, one pebble count at each cross section, 

and one site sketch with photographs of the bankfull channel 

for each site. Field data were analyzed to determine bankfull 

area, bankfull width, bankfull mean depth, and D50- and 

D84-particle size for two riffles at each site. 

Two sites were selected for duplicate surveys to 

establish whether the surveying techniques used in this study 

(2005–2006) produced similar results to the surveys (in 2003) 

for the regional curves of the Coastal Plain in Maryland. 

The comparisons of the duplicate surveys indicated that the 

Maryland regional curve data were similar to those collected 

in this study. The similarity of data allowed the creation of a 

composite dataset and the development of one set of bankfull 

regional curves for the Coastal Plain in Virginia and Maryland. 

Simple linear regression techniques were used to develop 

regional curves for the Coastal Plain representing Virginia and 

Maryland from two sources of data: (1) channel geometry data 

from 8 stations that were surveyed for this study in the Coastal 

Plain of Virginia and the Delmarva Peninsula of Maryland, 

and (2) data from 12 stations in Maryland that were not 

duplicated in this study for a total of 20 sites in the regression 

analysis. Bankfull cross-sectional area, bankfull width, 

bankfull mean depth, and estimated bankfull discharge—the 

response variables—were regressed against drainage area—the 

explanatory variable—to show the relation between drainage 

area and each response variable. The relatively high R2 value 

(0.945) for cross-sectional area indicates that it had the 

strongest linear relation to drainage area of the parameters 

measured. The R2 values for the other geometry parameters 

indicate that 89.0 percent, 87.1 percent, and 79.3 percent 

of the variability in each regional curve was explained by 

drainage area for bankfull width, mean depth, and bankfull 

discharge, respectively. 

The regional curves provide an estimate of bankfull 

geometry and serve as tools for field identification of bankfull 

features. They can be used in stream assessments of ungaged 

streams as a guide for identifying the expected natural-channel 

geometry in those streams. The regional curves are believed 

to be accurate within the prediction intervals for the range of 

drainage areas studied. Outside this range it is uncertain how 

far the regression relations may be extended with accuracy. 

The bankfull regional curves developed are applicable to 

non-urban streams in the non-tidal Coastal Plain areas of 

Virginia and Maryland. 

20 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
Acknowledgments

This project was funded in part by the Virginia Coastal 

Zone Management Program at the Department of Environmental Quality through Grant # NA03NOS4190194 of the 

National Oceanic and Atmospheric Administration, Office 

of Ocean and Coastal Management, under the Coastal Zone 

Management Act of 1972, as amended. This project was 

conducted as part of the Coastal Nonpoint Source Pollution 

Control Program as administered by the Virginia Department 

of Conservation and Recreation.

The authors thank Edward J. Doheny and Donald C. 

Hayes for assistance with site selection and calculation of 

site statistics. The authors thank Judith A. Okay, Samuel H. 

Austin, Curtis Hickman, and Shannon Kapsha for providing 

volunteer field assistance during data collection. In addition 

we thank our colleague reviewers, Jefferson N. Keaton, Judith 

A. Okay, and James M. Sherwood, for thorough, technical 

reviews of this report. 

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Leopold, L.B., Emmett, W.W., and Myrick, R.M., 1966, Channel 

and hillslope processes in a semi-arid area, New Mexico: U.S. 

Geological Survey Professional Paper 352G, p. 153–253. 

Leopold, L.B., Silvey, L.H., and Rosgen, D.L., 2000, The river 

field book: Pagosa Springs, CO, Wildland Hydrology, Inc., 

256 p. 

Leopold, L.B., Wolman, M.G., and Miller, J.P., 1964, Fluvial 

processes in geomorphology: New York, Dover Publications, 

Inc., 522 p. 

McCandless, T.L., 2003, Maryland stream survey—Bankfull discharge and channel characteristics in the coastal plain hydrologic region: U.S. Fish and Wildlife Service, Chesapeake Bay 

Field Office Report S03–02, 28 p. + app. 

McCandless, T.L., and Everett, R.A., 2002, Maryland stream survey—Bankfull discharge and channel characteristics of streams 

in the Piedmont hydrologic region: U.S. Fish and Wildlife 

Service, Chesapeake Bay Field Office Report S02–01, 40 p. 

+ app. A and B.

McFarland, E.R., and Bruce, T.S., 2006, The Virginia Coastal 

Plain hydrogeologic framework: U.S. Geological Survey 

Professional Paper 1731, 353 p.; accessed June 4, 2007, at 

http://pubs.water.usgs.gov/pp1731/

National Climate Data Center, 2005, U.S. Climate Atlas; accessed 

September 12, 2007, at http://www.ncdc.noaa.gov

Natural Resources Conservation Service, 2007, Regional hydraulic geometry curves; accessed March 28, 2007, at http://wmc.

ar.nrcs.usda.gov/technical/HHSWR/Geomorphic/index.html

Pickup, G., and Warner, R.F., 1975, Effects of hydrologic regime 

on magnitude and frequency of dominant discharge: Journal of 

Hydrology, v. 29, p. 51–75. 

Powell, R.O., Miller, S.J., Westergard, B.E., Mulvihill, C.I., 

Baldigo, B.P., Gallagher, A.S., and Starr, R.R., 2004, Guidelines for surveying bankfull channel geometry and developing 

regional hydraulic-geometry relations for streams of New York 

State: U.S. Geological Survey Open-File Report 03–92, 20 p. 

Richards, K.S., 1982, Rivers—Form and process in alluvial channels: New York, Methuen and Co., 357 p.

Rosgen, D.L., 1994, A classification of natural rivers: Catena, 

v. 22, p. 169–199. 

Rosgen, D.L., 1996, Applied river morphology (2d ed.): Pogosa 

Springs, CO, Wildland Hydrology, variously paged. 

Sherwood, J.M., and Huitger, C.A., 2005, Bankfull characteristics 

of Ohio streams and their relation to peak streamflows: U.S. 

Geological Survey Scientific Investigations Report 2005–5153, 

38 p.

Tasker, G.D., 1978, Relation between standard errors in log units 

and standard errors in percent: U.S. Geological Survey Water 

Resources Bulletin, January–March, April–June, p. 86–87. 

The MathWorks, Inc., 2006, MATLAB software package, version 

7.3.0.267 (R2006b). 

U.S. Census Bureau, 2004a, Census 2000 data for the District 

of Columbia; accessed June 4, 2007, at http://www.census.

gov/census2000/states/DC.html

U.S. Census Bureau, 2004b, Census 2000 data for the State of 

Maryland; accessed June 4, 2007, at http://www.census.gov/

census2000/states/md.html

U.S. Census Bureau, 2004c, Census 2000 data for the State of 

North Carolina; accessed June 4, 2007, at http://www.census.

gov/census2000/states/nc.html

U.S. Census Bureau, 2004d, Census 2000 data for the State of 

Virginia; accessed June 4, 2007, at http://www.census.gov/

census2000/states/va.html

U.S. Fish and Wildlife Service, 1979, Classification of wetlands 

and deepwater habitats of the United States: FWS/OBS-79/31, 

131 p.

U.S. Geological Survey, 2001, National elevation dataset; 

accessed July, 26, 2006, at http://ned.usgs.gov/

U.S. Geological Survey, 2003, User’s manual for the national 

water information system of the U.S. Geological Survey—

Automated data processing system (ADAPS): U.S. Geological 

Survey Open-File Report 03–89, version 4.2. 

Westergard, B.E., Mulvihill, C.I., Ernst, A.G., and Baldigo, B.P., 

2005, Regionalized equations for bankfull-discharge and channel characteristics of streams in New York State—Hydrologic 

region 5 in central New York: U.S. Geological Survey Scientific Investigations Report 2004–5247, 16 p.

White, K.E., 2001, Regional curve development and selection of a 

reference reach in the non-urban, lowland sections of the Piedmont Physiographic Province, Pennsylvania and Maryland: 

U.S. Geological Survey Water-Resources Investigations Report 

01–4146, 20 p.

Williams, G.P., 1978, Bank-full discharge of rivers: Water 

Resources Research, v. 14, no. 6, p. 1141–1154.

Wolman, M.G., 1954, A method of sampling coarse river-bed 

material: Transactions of American Geophysical Union, v. 35, 

p. 951–956.

Wolman, M.G., and Miller, J.C., 1960, Magnitude and frequency 

of forces in geomorphic processes: Journal of Geology, v. 68 p. 

54–74.
Appendix 1—Streamflow-Gaging Station Numbers, Site Descriptions and 

Photographs, Longitudinal Profiles, Riffle Cross Sections, and Bed Material 

Particle-Size Distributions of Cross Sections

Station 01674700, Aylett Creek at Aylett, VA....................................................................................................................................24

Figure A1. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2 in the study reach of 

Aylett Creek at Aylett, VA, May 24, 2005 ...................................................................................................................................25

Figure A2. Particle-size distribution of bed material in the study reach of Aylett Creek at Aylett, VA, May 24, 2005 ...................................26

Station 02042250, Bailey Branch Tributary at Spring Grove, VA..................................................................................................27

Figure A3. (A) Longitudinal profile, (B) riffle cross secton 1, and (C) riffle cross section 2 in the study reach of 

Bailey Branch Tributary at Spring Grove, VA, May 26, 2005 ......................................................................................................28

Figure A4. Particle-size distribution of bed material in the study reach of Bailey Branch Tributary at 

Spring Grove, VA, May 26, 2005.................................................................................................................................................29

Station 01661800, Bush Mill Stream near Heathsville, VA............................................................................................................30

Figure A5. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2 in the study reach of 

Bush Mill Stream near Heathsville, VA, May 19, 2005 ..............................................................................................................31

Figure A6. Particle-size distribution of bed material in the study reach of Bush Mill Stream near 

Heathsville, VA, May 19, 2005....................................................................................................................................................32

Station 01668500, Cat Point Creek near Montross, VA...................................................................................................................33

Figure A7. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2 in the study reach of 

Cat Point Creek near Montross, VA, May 17, 2005 ....................................................................................................................34

Figure A8. Particle-size distribution of bed material in the study reach of Cat Point Creek near 

Montross, VA, May 17, 2005 ......................................................................................................................................................35

Station 01491000, Choptank River near Greensboro, MD..............................................................................................................36

Figure A9. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2 in the study reach 

of Choptank River near Greensboro, MD, September 1, 2005 ...................................................................................................38

Figure A10. Particle-size distribution of bed material in the study reach of Choptank River near 

Greensboro, MD, September 1, 2005 .........................................................................................................................................39

Station 02042710, Collins Run Tributary near Providence Forge, VA..........................................................................................40

Figure A11. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2 in the study reach of 

Collins Run Tributary near Providence Forge, VA, July 15, 2005, and May 6, 2006...................................................................41

Figure A12. Particle-size distribution of bed material in the study reach of Collins Run Tributary near 

Providence Forge, VA, July 15, 2005, and May 6, 2006 .............................................................................................................42

Station 01492550, Mill Creek near Skipton, MD..............................................................................................................................43

Figure A13. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2 in the study reach of 

Mill Creek near Skipton, MD, April 12, 2006..............................................................................................................................44

Figure A14. Particle-size distribution of bed material in the study reach of Mill Creek near 

Skipton, MD, April 12, 2006........................................................................................................................................................45

Station 01674200, Reedy Creek near Dawn, VA ..............................................................................................................................46

Figure A15. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2 in the study reach of 

Reedy Creek near Dawn, VA, May 11, 2005...............................................................................................................................47

Figure A16. Particle-size distribution of bed material in the study reach of Reedy Creek near Dawn, VA, May 11, 2005 .............................48

Appendix  23
Station 01674700

Aylett Creek at Aylett, VA

 View looking upstream at reach of Aylett Creek at Aylett, VA

The study reach for Aylett Creek was 920 ft long and included gages located at stations 258 and 338. The reach is bisected 

by a divided four-lane bridge. The west-bound lanes, on the upstream side of the reach, pass over a bridge, which has a scour 

hole underneath. Between the east- and west-bound lanes there is an area of deposition with a point bar on the left bank that 

almost cuts off flow to the left-most box of a 3-box culvert. The east-bound lanes pass over the 3-box culvert. The upstream 

and downstream crest-stage partial-record streamflow-gaging stations (CSG) were mounted on the bridge abutment for the 

east-bound lanes. Thirty feet downstream from the culvert there is a large scour hole 5 ft deep. There were large sand deposits 

along the banks at an elevation higher than bankfull for at least 200 ft below the culvert. They may be from recent hurricanes 

(Hurricane Gaston 2004) which brought intense rainfall to this area. It is likely that swift flows through the culvert and some 

straightening during the bridge construction influence the straight section of stream for 150 ft below the culvert. After 150 ft 

the stream became more sinuous. The cross sections were located toward the end of the reach in a part of the channel that was 

relatively unaffected by the culvert. Approximately 1,500 ft below the end of the reach, the channel becomes divided and flows 

into a swamp. 

The reach was narrow with deep pools (4 ft). Pools and runs dominated the reach, with riffles identifiable by particle size 

and depth. The slope was gradual with a few slight jumps making it somewhat difficult to identify riffles. The bed material was 

sand and small gravel with sand dominant except in the riffles. Coarse woody debris created short backwater areas and increased 

roughness in the channel. Often the woody debris was a contributor to pool formation.

Bankfull features along this reach were located at the top of the bank. The banks were stable with little erosion. The banks 

were stabilized by large small and trees with some grass. The active floodplain was covered with a mix of young trees, understory herbaceous plants, vines, and some manicured grass. The left bank was a residential area with a forested buffer of 50 to 

300 ft along the reach. The right bank was forested. 

24  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
-1

-2

-3

-4

-5

4

3

2

1

0

0 100 200 300 400 500 600 700 800 900 1,000

Cross section 2 Cross section 1 Streamflow-gaging station 1 Streamflow-gaging station 2

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET Thalweg

Water surface

Bankfull best-fit line

2-year recurrence interval

1-year recurrence interval

(A)

Figure A1. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2, in the study reach of Aylett Creek at Aylett, VA, May 24, 2005.

0

10

20

30

0 20 40 60 80 100 120

(B)

Cross section 1Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET 86

4

2

0

10

12

14

16

18

20

0 10 20 30 40 50 60 70 80 90 100

(C)

Cross section 2Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Appendix  25
0.01 0.1 1 10 100 1,000 10,000

0

10

20

30

40

50

60

70

80

90

100

PARTICLE SIZE, IN MILLIMETERS

PERCENT FINER THAN

Composite material

Size classification, in percent Percent finer, in millimeters

Siltclay Sand Gravel Cobble Boulder Bedrock D16 D50 D84

Total count = 206

7.77 41.26 50.97 0.00 0.00 0.00 0.25 4.00 8.00

Figure A2. Particle-size distribution of bed material in the study reach of Aylett Creek at Aylett, VA, May 24, 2005.

26  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
Station 02042250

Bailey Branch Tributary at Spring Grove, VA

 View looking upstream at reach of Bailey Branch Tributary at Spring Grove, VA 

The study reach at Bailey Branch Tributary was 300 ft long, ending at the location of the upstream crest-stage partial-record 

streamflow-gaging station (CSG). For the next 58 ft, the creek passes through a 2-box culvert which likely has some backwater 

affect at bankfull stage. At two locations (station 150 and 290) along the reach there were springs that contribute to the flow. The 

stream was more sinuous at the top of the reach with two major bends up to station 120 and then was relatively straight until the 

culvert where it turns to the right to pass under the road. 

The stream was narrow and shallow with few depths deeper than 1 ft during the time of survey. Throughout the reach the 

channel maintained a riffle-run-pool sequence. Slopes at riffles within this reach were visible during the survey, making this 

site slightly different than most of the other sites in this study. The bed material was dominated by gravel and sand with gravel 

present in the runs as well as riffles. A little cobble was present in the riffles. Much coarse woody debris was embedded in the 

channel. The floodplain slope was roughly 14 percent on the left bank of cross section 1, which is a much greater slope than 

other sites in this study. The valley shape and channel slope give this site the appearance of a Piedmont stream, but it is 

in the Coastal Plain. 

Bankfull features in this reach were low benches on the inside of a slightly entrenched channel. Two sets of bankfull 

features were surveyed here, the benches and top of the bank, but the top of the bank represents a 5-year flood or higher. The 

river may be forming new bank features within a previously used channel. The low-banks seem to fit with a 1-year event. The 

stream banks were heavily vegetated with herbaceous plants such as ferns, jewelweed, vines, grasses, and moss. Watercress was 

growing across at least half of the channel width at the two spring locations. The active floodplain contained mature deciduous 

trees, such as tulip, beech, maple, and sycamore, with a developing under-story of shrubs including privet and multiflora rose for 

50 ft on either side of the channel. 

Appendix  27
6

5

4

3

2

1

0

0 50 100 150 200 250 300 350 400

Cross section 2 Cross section 1

Thalweg

Water surface

Bankfull best-fit line

2-year recurrence interval

1-year recurrence interval

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

(A)

9

8

7

6

5

4

3

2

10

1112

13

14

1516

17

0 5 10 15 20 25 30 35 40 45 50 55 60

(B)

Cross section 1Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

98

7

65

4

3

2

101112

13

14

15

16

17

0 5 10 15 20 25 30 35 40 45 50 55 60

(C)

Cross section 2Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Figure A3. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2, in the study reach of Bailey Branch Tributary at Spring Grove, VA, May 26, 2005. 

Streamflow-gaging station 1 Streamflow-gaging station 2

28 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
Composite material

SiltClay Sand Gravel Cobble Boulder Bedrock D16 D50 D84

Total count = 231

6.06 22.08 69.70 2.16 0.00 0.00 0.50 11.00 32.00

0

10

20

30

40

50

60

70

80

90

100

PERCENT FINER THAN

0.01 0.1 1 10 100 1,000 10,000

PARTICLE SIZE, IN MILLIMETERS

Figure A4. Particle-size distribution of bed material in the study reach of Bailey Branch Tributary at

Spring Grove, VA, May 26, 2005.

Size classification, in percent Percent finer, in millimeters

Appendix  29
Station 01661800

Bush Mill Stream near Heathsville, VA

 View looking downstream at reach of Bush Mill Stream near Heathsville, VA 

The study reach at Bush Mill Stream was 530 ft long, ending at the location of the continuous-record streamflow-gaging 

station (CRG) just upstream from a 2-lane bridge with a 4-box culvert. There seems to be little backwater affect from the bridge 

at bankfull stage. An old railroad- or road-grade crosses the stream near station 300. This raised elevation of 10 ft above bankfull 

does not appear to affect the stream, but bankfull features in that section could not be identified. Cross section 1 was located at 

station 104. At station 270, a small tributary enters on the right bank and many of the bankfull features were lower in this part of 

the reach than upstream. Overland flow from the small tributary probably contributes to bank erosion in this section, making the 

bankfull features lower. After the tributary, Bush Mill Stream takes a turn to the left and flows straight to the CRG from station 

300 to 530. Cross section 2 was in this section at station 428. Station 270 appears to be a dividing point between a narrow, 

sinuous channel with slightly higher bankfull features and a wide, straight channel, which may have been altered when the road 

was constructed. 

The channel was run-pool dominated with riffles identifiable by particle size and depth. The slope was gradual with a few 

slight jumps making it somewhat difficult to identify riffles. The bed material was almost entirely sand with a minor amount of 

gravel present in the riffles. Coarse woody debris and fallen trees added to the roughness within the channel and created small 

backwater areas. 

Bankfull features selected in this reach represent the top of the bank. The break in slope was surveyed but considered too 

low. Banks were heavily vegetated with herbaceous vegetation, saplings, and some large trees including maple, oak, sycamore, 

and holly. Many of the bends in the river occurred at large, mature trees, which appeared to be stabilizing the banks. In the upper 

section of the reach there were undercut banks, but erosion was not common along the reach. The active floodplain was forested 

with mostly young trees, few mature trees, and green briar (smilax), and was heavily vegetated with grass. 

30 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
-1

-2

-3

8

7

6

5

4

3

2

1

0

0 100 200 300 400 500 600

Thalweg

Water surface

Bankfull best-fit line

2-year recurrence interval

1-year recurrence interval

Cross section 2 Cross section 1

(A)

Streamflow-gaging station

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

0

10

2030

40

0 20 40 60 80 100 120

(B)

Cross section 1Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

-

50

5

1015202530354045

0 10 20 30 40 50 60 70 80 90 100

(C)

Cross section 2Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Figure A5. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2, in the study reach of Bush Mill Stream near Heathsville, VA, May 19, 2005.

Appendix  31
0.01 0.1 1 10 100 1,000 10,000

0

10

20

30

40

50

60

70

80

90

100

PARTICLE SIZE, IN MILLIMETERS

PERCENT FINER THAN

Figure A6. Particle-size distribution of bed material in the study reach of Bush Mill Stream near Heathsville, VA,

May 19, 2005.

Composite material

Size classification, in percent Percent finer, in millimeters

Siltclay Sand Gravel Cobble Boulder Bedrock D16 D50 D84

Total count = 219

17.35 73.52 9.13 0.00 0.00 0.00 0.06 0.50 2.00

32  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
Station 01668500

Cat Point Creek near Montross, VA

 View looking upstream at reach at Cat Point Creek near Montross, VA 

The study reach at Cat Point Creek was 935 ft long, ending 85 ft downstream from the location of the continuous-record 

streamflow-gaging station (CRG) at the upstream end of a 2-lane bridge. There had been disturbance in the vicinity of the gage 

prior to its discontinuation. The location of the gage was close to an old road-grade, with wooden bridge pylons still present 

in the channel. A small tributary that enters on the right bank had washed out the land around the gage and caused the gage to 

fall into the river. At the mouth of the small tributary there was a scour hole with a mid-channel sand bar between the gage and 

the bridge downstream. The upstream 800 ft of reach were relatively unaffected by anthropogenic forces. There was a natural 

sinuosity throughout the reach. 

The creek was wide with deep holes that were undetectable because the water was murky brown with little light penetration, likely because of tannins in the water. The channel was run-pool dominated with riffles only identifiable by particle size 

and depth. The slope was gradual with a few slight jumps making it somewhat difficult to identify riffles. The bed material 

was almost entirely sand with a minor amount of very small gravel present in some riffles. Coarse woody debris added to the 

roughness within the channel and often seemed to contribute to riffle formation. 

The bankfull features were predominantly the top of the bank, although many low point bars, or benches, were forming. 

These were surveyed, but considered too low and inconsistent. The top of the bank was the highest feature for at least 100 ft 

away from the channel in either direction. The banks were heavily vegetated with herbaceous cover, shrubs, small saplings, and 

some large deciduous trees. There was a buffer of trees and shrubs for at least 10 ft on either side of the creek, including maple, 

birch, beech, and ironwood trees. The active floodplain on the right bank was forested; however, the left bank was an emergent 

wetland with arrow-head, pond lily, hibiscus, grass, and sedges with some birch trees. There was standing water in rivulets 

throughout the floodplain, but much of the land surface was dry during the survey. 

Appendix  33
-2

-4

8

6

4

2

0

10

0 100 200 300 400 500 600 700 800 900 1,000

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Streamflow-gaging station Cross section 2 Cross section 1

Thalweg

Water surface

Bankfull best-fit line

2-year recurrence interval1-year recurrence interval

(C)

-

5

0

5

10

15

20

25

30

35

40

45

505560

65

70

75

0 50 100 150 200 250 300

Cross section 2Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Figure A7. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2, in study reach of Cat Point Creek near Montross, VA, May 17, 2005.The water-surface elevation (WSL) rose 0.24 ft during the longitudinal profile survey. The difference in WSL between station 615 and 625 is not due to a dam,but rather the difference in WSL from rainfall. 

(A)

(B)

-

5

0

5

1015

20

25

303540

45

50

340 360 380 400 420 440 460 480 500 520 540 560 580 600

Cross section 1Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

34  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
0.01 0.1 1 10 100 1,000 10,000

0

10

20

30

40

50

60

70

80

90

100

PARTICLE SIZE, IN MILLIMETERS

PERCENT FINER THAN

Figure A8. Particle-size distribution of bed material in the study reach of Cat Point Creek near Montross, VA,

May 17, 2005.

Composite material

Size classification, in percent Percent finer, in millimeters

Siltclay Sand Gravel Cobble Boulder Bedrock D16 D50 D84

Total count = 207

0.48 99.52 0.00 0.00 0.00 0.00 0.50 1.00 2.00

Appendix  35
Station 01491000

Choptank River near Greensboro, MD

 View looking upstream at reach of Choptank River near Greensboro, MD

 View of weir and streamflow-gaging station on the left bank 

 at reach of Choptank River near Greensboro, MD

36  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
The study reach at Choptank River was 1,300 ft long, ending downstream of the continuous-record streamflow-gaging 

station (CRG) and weir, which were located at station 1135. The weir had a significant affect on the water-surface profile 

through the study reach. The weir may have contributed to a back water effect throughout the reach. Upstream from the weir was 

an old roadbed with a depression wetland on the left bank. Downstream from the weir there was a deep scour pool. This site had 

the largest drainage area available for the study and also served as a comparison stream with McCandless (2003). 

The stream was wide with consistent widths and depths. The bed material was a mixture of gravel and sand, with small 

gravel dominating in the riffles. The large amount of coarse woody debris in the form of mature tree trunks and limbs influenced 

sediment deposition patterns and scour. 

Bankfull features in the reach were represented by the top of the bank, although lower features were surveyed. There were 

breaks in slopes that were considered too low. 

The vegetation on the banks was made of herbaceous plants, briars (smilax), small saplings, shrubs, and mature trees. The 

banks contained cut banks and scour holes around the coarse woody debris. The active floodplain was forested wetland with 

deciduous trees, such as box elder, maple, oak, and birch. 

Appendix  37
-4

-3

-2

-

98

7

65

4

3

2

1

0

1

10

0 200 400 600 800 1,000 1,200 1,400

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Streamflow-gaging station Cross section 2 Cross section 1

Thalweg

Water surface

Bankfull best-fit line

2-year recurrence interval

1-year recurrence interval

(A)

Figure A9. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2, in the study reach of Choptank River near Greensboro, MD September 1, 2005.

-2

8

4838

2818

0 20 40 60 80 100 120 140 160 180 200

(B)

Cross section 1Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

-5

5

45

35

25

15

0 20 40 60 80 100 120 140 160 180 200

(C)

Cross section 2Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

38 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
0.01 0.1 1 10 100 1,000 10,000

0

10

20

30

40

50

60

70

80

90

100

PARTICLE SIZE, IN MILLIMETERS

PERCENT FINER THAN

Composite material

Size classification, in percent Percent finer, in millimeters

Siltclay Sand Gravel Cobble Boulder Bedrock D16 D50 D84

Total count = 259

7.34 31.66 61.00 0.00 0.00 0.00 0.50 11.00 23.00

Figure A10. Particle-size distribution of bed material in the study reach of Choptank River near Greensboro, MD,

September 1, 2005.

Appendix  39
Station 02042710

Collins Run Tributary near Providence Forge, VA

 View looking upstream at reach of Collins Run Tributary near Providence Forge, VA 

The study reach at Collins Run Tributary was 475 ft long, ending just downstream from an 85-ft-long single-box culvert. 

The upstream and downstream crest-stage partial-record streamflow-gaging stations (CSG) had been bolted to the wing walls of 

the culvert. The culvert opening was only 4 ft high and 4 ft wide, and given the low bankfull features near the culvert, it is likely 

that it causes a backwater affect at bankfull flows. The channel seemed to be transitioning with some scour and undercut banks, 

but bankfull features were identifiable. 

The stream was narrow and shallow with few depths deeper than 1.5 ft during the time of survey. Throughout the reach the 

channel maintained a riffle-run-pool sequence. Slopes at riffles within this reach were easily identifiable during the survey as 

well as coarse bed material. The bed material was dominated by sand with small gravel present in the riffles. 

Bankfull features in this reach were low benches on the inside of a slightly entrenched channel. There are many banks 

that are undercut with new point bars forming within the entrenched channel. The features that were selected are the low banks 

throughout the survey. The low banks, which were surveyed, seem to represent a slightly less than 1-year event. The banks 

were not highly vegetated throughout the reach. Many were covered with grass, ferns, and moss, but often sand and clay were 

exposed. The buffer and floodplain was a young forest with deciduous trees, including oak, sweet gum, sycamore, tulip, and 

holly. The understory was dominated by upland plants and was abundant with small Pawpaw trees and understory shrubs. 

40 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
9

8

7

6

5

4

3

2

1

0

10

50 150 250 350 450 550 650

ELEVATION, IN FEET

Streamflow-gaging station 1 Streamflow-gaging station 2 Cross section 2 Cross section 1

Thalweg

Water surface Bankfull best-fit line

2-year recurrence interval

(A)

CHANNEL DISTANCE, IN FEET

8

6

4

2

10

12

14

60 65 70 75 80 85 90 95 100 105 110

(B)

Cross section 1Water surfaceBankfull stageFloodprone stage

ELEVATION, IN FEET

CHANNEL DISTANCE, IN FEET

50

1015

20

25

0 10 20 30 40 50 60 70 80 90

(C)

Cross section 2Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Figure A11. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2, in the study reach of Collins Run Tributary near Providence Forge, VA,July 15, 2005 and May 6, 2006.

Appendix  41
0.01 0.1 1 10 100 1,000 10,000

0

10

20

30

40

50

60

70

80

90

100

PARTICLE SIZE, IN MILLIMETERS

PERCENT FINER THAN

Composite material

Size classification, in percent Percent finer, in millimeters

Siltclay Sand Gravel Cobble Boulder Bedrock D16 D50 D84

Total count = 212

10.85 42.92 46.23 0.00 0.00 0.00 0.13 2.00 8.00

Figure A12. Particle-size distribution of bed material in the study reach of Collins Run Tributary near Providence

Forge, VA, July 15, 2005, and May 6, 2006.

42  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
Station 01492550

Mill Creek near Skipton, MD

 View looking downstream from cross section 2 at reach of Mill Creek near Skipton, MD

The study reach at Mill Creek was 1,000 ft long, passing through a 2-box culvert under a two-lane bridge for a length of 

100 ft, then ending 125 ft downstream. The discontinued crest-stage partial-record streamflow-gaging station (CSG) had been 

located on the upstream side of the bridge at station 750. While the bridge did not seem to have much backwater affect on the 

reach, the numerous wetland drainages into the reach had an effect on the elevation of the bankfull features. The reach had one 

large drain that appeared to be a side-channel pond. 

The stream was narrow in the upper reaches and widened downstream. It was dominated by run-pool sequences. The riffles 

were somewhat difficult to identify because of the slight change in channel slope throughout the reach. The bed material was 

entirely sand, with much coarse woody debris, increasing the channel roughness slightly. 

The bankfull features selected were located at the top of the bank. Bankfull features were slightly lower than the 1-year 

recurrence interval. This site was one surveyed by McCandless (2003) who adjusted the peak-flow analysis to remove an outlier; 

thus, the calculation of recurrence interval by McCandless is slightly higher than the one presented in this report because of the 

difference in peak-flow statistic calculations. 

The vegetation on the banks was herbaceous with small shrubs, saplings, and some mature deciduous trees. In the active 

floodplain, red maple made up the overstory, with an understory of privet, multiflora rose, and skunk cabbage within hydric 

soils and standing water. On the left bank near station 500, the valley slope increased, and the vegetation changed to an upland 

community of beech, maple, and oak. 

Appendix  43
7

6

5

43

2

1

0

-50 150 350 550 750 950 1,150

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Streamflow-gaging station Cross section 2 Cross section 1

Thalweg

Water surface

Bankfull best-fit line

(A)

Figure A13. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2, in the study reach of Mill Creek near Skipton, MD, April 12, 2006.

2-year recurrence interval

1-year recurrence interval

8

6

4

2

0

10

12

14

16

18

10 20 30 40 50 60 70 80

(B)

Cross section 1Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

0

1020

130 140 150 160 170 180 190 200 210 220 230

(C)

Cross section 2Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

44  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
0.01 0.1 1 10 100 1,000 10,000

0

10

20

30

40

50

60

70

80

90

100

PARTICLE SIZE, IN MILLIMETERS

PERCENT FINER THAN

Composite material

Size classification, in percent Percent finer, in millimeters

Siltclay Sand Gravel Cobble Boulder Bedrock D16 D50 D84

Total count = 197

20.30 79.70 0.00 0.00 0.00 0.00 0.06 0.50 2.00

Figure A14. Particle-size distribution of bed material in the study reach of Mill Creek near Skipton, MD,

April 12, 2006.

Appendix  45
Station 01674200

Reedy Creek near Dawn, VA

 View looking downstream at reach of Reedy Creek near Dawn, VA 

The study reach at Reedy Creek was 810 ft long, passing under a bridge in the center of the reach at station 386 for a 

length of 41 ft, and then continuing 383 ft downstream. The discontinued crest-stage partial-record streamflow-gaging station 

(CSG) had been bolted to the upstream wing wall of the bridge at station 381. The bridge had a deep scour pool downstream for 

approximately 20 ft. There was a backwater effect in the vicinity of the bridge during the survey due to the presence of a small 

beaver dam at station 544. The beaver dam was not at the bankfull elevation, so it was assumed that the influence would not be 

great during bankfull flows. 

The stream was consistently wide throughout the reach, dominated by shallow runs less than 2 ft deep during the survey 

and pools of 5 ft or less during the survey. The riffles were easy to identify, though they were often formed by the woody debris 

in the channel. Bed material was dominated by sand, but contained small gravel and a little cobble in riffles. 

Bankfull features surveyed in this reach were the top of the bank, although lower features were surveyed. The most 

consistent features between the longitudinal profile and cross-section surveys were represented by the top of the bank. For more 

than 60 ft on either side of the channel there was little gain in elevation. The banks and flood plain were densely vegetated 

with herbaceous vegetation and shrubs, —green briar (smilax), blueberry, dog wood, and privet—and mature deciduous 

trees—maple, oak, and holly. The floodplain contained pockets of forested wetland on both banks upstream and downstream 

from the gage. 

46  Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
-4

-3

-2

-

65

4

3

2

1

0

1

0 100 200 300 400 500 600 700 800 900

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Streamflow-gaging station Cross section 2 Cross section 1

Thalweg

Water surface

Bankfull best-fit line

2-year recurrence interval

1-year recurrence interval

(A)

50

1015202530

5 25 45 65 85 105 125

(B)

Cross section 1Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

5

0

10

15

20

25

30

0 20 40 60 80 100 120

(C)

Cross section 2Water surfaceBankfull stageFloodprone stage

CHANNEL DISTANCE, IN FEET

ELEVATION, IN FEET

Figure A15. (A) Longitudinal profile, (B) riffle cross section 1, and (C) riffle cross section 2, in the study reach of Reedy Creek near Dawn, VA, May 11, 2005. 

Appendix  47
0.01 0.1 1 10 100 1,000 10,000

0

10

20

30

40

50

60

70

80

90

100

PARTICLE SIZE, IN MILLIMETERS

PERCENT FINER THAN

Composite material

Size classification, in percent Percent finer, in millimeters

Siltclay Sand Gravel Cobble Boulder Bedrock D16 D50 D84

Total count = 208

0.96 50.96 47.12 0.96 0.00 0.00 0.25 2.00 16.00

Figure A16. Particle-size distribution of bed material in the study reach of Reedy Creek near Dawn, VA,

May 11, 2005.

48 Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain Province, Virginia and Maryland
Prepared by:

USGS Enterprise Publishing Network

Raleigh Publishing Service Center

3916 Sunset Ridge Road

Raleigh, NC 27607

For additional information regarding this publication, contact:

Jennifer L. Krstolic

U.S. Geological Survey

1730 East Parham Road

Richmond, VA 23228

phone: 804-261-2635

email: jkrstoli@usgs.gov

Or visit the Virginia Water Science Center website at:

http://va.water.usgs.gov
Krstolic and Chaplin—Bankfull Regional Curves for Streams in the Non-Urban, Non-Tidal Coastal Plain, VA and MD—Scientific Investigations Report 2007–5162

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