y = 17.6x0.662

R2 = 0.89 

y = 16.9x0.419

R2 = 0.79 

0.1

1

10

100

1,000

0.1 1 10 100 1,000

DRAINAGE AREA, IN SQUARE MILES 

BANKFULL CHANNEL WIDTH AND DEPTH, IN FEET,

AND CROSS-SECTIONAL AREA, IN SQUARE FEET

y = 1.04x0.244

R2 = 0.64 

× × ××

×

×

×

× ×

×

×

××

× ×

×

×

×

×

×

×

×

×

×

×

×

×

××

×× ×

× ×

× × ××

× ×

×

×

Bankfull channel width

Bankfull channel depth

Bankfull channel cross-sectional area

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2005–5100

Regionalized Equations for Bankfull Discharge and 

Channel Characteristics of Streams in New York State:

Hydrologic Region 6 in the Southern Tier of New York

In cooperation with

New York State Department of Environmental Conservation

New York State Department of Transportation

New York City Department of Environmental Protection
This page has been left blank intentionally. 
Regionalized Equations for Bankfull 

Discharge and Channel Characteristics of 

Streams in New York State:

Hydrologic Region 6 in the Southern Tier of 

New York

By Christiane I. Mulvihill, Anne G. Ernst, and Barry P. Baldigo

Scientific Investigations Report 2005–5100

In cooperation with

New York State Department of Environmental Conservation

New York State Department of Transportation

New York City Department of Environmental Protection

U.S. Department of the Interior

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

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2005

Version 1.01

For additional information about this report write to:

U.S. Geological Survey

425 Jordan Road

Troy, NY 12180

Email: askny@usgs.gov

World Wide Web: http://ny.usgs.gov/

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

World Wide Web: http://www.usgs.gov/

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

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 6 in the Southern Tier of New York: U.S. Geological 

Survey Scientific Investigations Report 2005-5100, 14 p., online only.
Contents

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

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

Approach................................................................................................................................................2

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

Methods...........................................................................................................................................................4

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

Data Collection......................................................................................................................................4

Data Analysis.........................................................................................................................................5

Regional Equations for Bankfull Discharge and Channel Characteristics of Streams ......................5

Regionalized Relation between Bankfull Discharge and Drainage-Area Size...........................5

Bankfull Discharge Recurrence Intervals ........................................................................................7

Stream-Channel Dimensions in Relation to Drainage-Area Size ................................................7

Stream and Reach Classification.......................................................................................................8

Region 6 Equation in Relation to those Developed for Other Areas.............................................8

Limitations of This Study.............................................................................................................................13

Summary and Conclusions.........................................................................................................................13

Acknowledgements.....................................................................................................................................14

References Cited..........................................................................................................................................14

Figures

1. Map showing hydrologic regions in New York: A. Hydrologic-region boundaries as 

defined by Lumia (1991). B. Locations of the 11 active and 3 inactive streamflow-gaging 

stations used in 2002-03 stream survey in Region 6 ...........................................................................3

2. Graph showing bankfull discharge as a function of drainage-area size for streams 

surveyed in Region 6 in New York, with 95-percent confidence and prediction intervals 

for all sites..................................................................................................................................................7

3. Graph showing bankfull channel width, depth, and cross-sectional area as a function of 

drainage-area size for all streams surveyed in Region 6 in New York, with best-fit lines, 

regression equations, and coefficient of determination (R2) values ................................................8

4. Graph showing mean channel dimensions as a function of drainage-area size for streams 

in Region 6 in New York, with 95-percent confidence and prediction intervals: A. Bankfull 

channel width. B. Bankfull channel depth. C. Bankfull channel cross-sectional area.................9

5. Graph showing bankfull discharge as a function of drainage-area size for Region 6 in New 

York, and published curves for four other regions in the Northeast..............................................12

Tables

1. Characteristics of streamflow-gaging stations surveyed in Region 6 in New York, 

2002-03 ..................................................................................................................................................6

 2. Stream classification and bankfull channel-geometry data for cross sections at the 14 

streamflow-gaging stations surveyed in Region 6 in New York, 2002-03 ....................................10

iii
Conversion Factors and Datum

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

foot per second (ft/s) 0.3048 meter per second (m/s)

Area

square mile (mi2) 2.590 square kilometer (km2)

Flow Rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)/1.8

Vertical coordinate information is referenced to the North American Vertical Datum 

of 1988 (NAVD 88).

Horizontal coordinate information is referenced to the North American Datum 

of 1983 (NAD 83).

iv
Abstract

Equations that relate bankfull discharge and channel 

characteristics (width, depth, and cross-sectional area) to 

drainage-area size at gaged sites are needed to define bankfull 

discharge and channel dimensions at ungaged sites and to 

provide information for watershed assessments, streamchannel classification, and the design of stream-restoration 

projects. Such equations are most accurate if derived from 

streams within an area of uniform hydrologic, climatic, 

and physiographic conditions and applied only within that 

region. In New York State, eight hydrologic regions were 

previously defined on the basis of similar high-flow (flood) 

characteristics. This report presents drainage areas and 

associated bankfull characteristics (discharge and channel 

dimensions) for surveyed streams in southwestern New York 

(Region 6). 

Stream-survey data and discharge records from 11 active 

(currently gaged) sites and 3 inactive (discontinued) sites were 

used in regression analyses to relate bankfull discharge and 

bankfull channel width, depth, and cross-sectional area to the 

size of the drainage area. The resulting equations are: 

bankfull discharge (ft3/s) = 48.0 (drainage area, in mi2)

0.842

bankfull channel width (ft) = 16.9 (drainage area)0.419

bankfull channel depth (ft) = 1.04 (drainage area)0.244

bankfull channel cross-sectional area (ft2) = 17.6 

(drainage area)0.662

The coefficient of determination (R2) for these four 

equations were 0.90, 0.79, 0.64, and 0.89, respectively. The 

high correlation coefficients for bankfull discharge and 

cross-sectional area indicate that much of the variation in 

these variables is explained by the size of the drainage area. 

The smaller correlation coefficients for bankfull channel 

width and depth indicate that other factors also affect these 

relations. Recurrence intervals for the estimated bankfull 

discharge of each stream ranged from 1.01 to 2.35 years; the 

mean recurrence interval was 1.54 years. The 14 surveyed 

streams were classified by Rosgen stream type; most were 

C-type reaches, with occasional B-type reaches. The Region 

6 equation (curve) for bankfull discharge was compared 

with equations previously developed for four other large 

areas in New York State and southeastern Pennsylvania. 

The differences among results indicate that, although the 

equations need to be refined by region before being applied 

by water-resources managers to local planning and design 

efforts, similar regions have similar relations between bankfull 

discharge and channel characteristics.

Introduction

Streambank erosion and the resulting sedimentation 

in streams can affect the water quality of reservoirs and 

endanger private and public lands and associated infrastructure 

across New York State. Many streams throughout New York 

State that have abnormally high rates of bank erosion and 

sedimentation are undergoing restoration efforts to improve 

bank and bed stability (Miller and Davis, 2003). Stream 

restorations have traditionally consisted of procedures such as 

straightening, widening, and deepening the channel, hardening 

the banks, and imposing static stream geometry—all of 

which can cause permanent ecological disruption. Recent 

stream-restoration projects, however, have begun to use 

an approach that strives toward replication of stable-reach 

characteristics, such as the relation between drainage-area 

size and channel cross-section dimensions, and the relations 

among channel dimensions, flow patterns, and water-surface 

profiles. Equations (models or curves) defining these relations 

developed from stable-reach data at gaged streams can provide 

a basis for channel restorations in nearby unstable, ungaged 

streams and for replication of geomorphically stable reaches 

that support healthy ecosystems.

The most important variable in calculating the relations 

between drainage-area size and stream-channel dimensions 

is bankfull discharge, which corresponds to the point of 

transition between the channel and its flood plain (Leopold 

and others, 1964), and is the stage or flow at which the 

stream is about to overtop its banks onto the flood plain 

(Leopold and others, 1964; Leopold, 1994). Bankfull 

discharge is reported to occur every 1 to 2 years, or 1.5 years 

Regionalized Equations for Bankfull Discharge and 

Channel Characteristics of Streams in New York State:

Hydrologic Region 6 in the Southern Tier of New York

By Christiane I. Mulvihill, Anne G. Ernst, and Barry P. Baldigo
on average (Rosgen, 1994), and is the flo erage (Rosgen, 1994), and is the flow that mow that moves the 

most sediment o most sediment over time, because of the combination of its er time, because of the combination of its 

force and frequenc force and frequency (Wolman and Miller olman and Miller, 1960; Leopold, , 1960; Leopold, 

1994). The characteristics of bankfull dischar 1994). The characteristics of bankfull discharge affect the fect the 

relations between drainage-area size and stream-channel 

dimensions in tw dimensions in two ways. First, bankfull dischar ays. First, bankfull discharge often occurs ge often occurs 

at a relatiat a relatively discrete and identif ely discrete and identifiable stage and, therefore, iable stage and, therefore, 

provides a basis for a system to classify streams in terms of vides a basis for a system to classify streams in terms of 

channel dimensions at bankfull stage (Rosgen, 1996). Second, 

relations between drainage area and dischar relations between drainage area and discharge, and between ge, and between 

drainage area and channel dimensions, are relati drainage area and channel dimensions, are relatively constant ely constant 

at bankfull stage in stable streams of the same class and within 

the same hthe same hydrophysiographic re ysiographic region (Leopold and others, gion (Leopold and others, 

1964; Rosgen, 1996). 

Predicting stable-channel characteristics for an unstable, 

ungaged stream requires equations based on data from stable, aged stream requires equations based on data from stable, 

gaged streams that are close to the ung aged streams that are close to the ungaged stream; are subject aged stream; are subject 

to similar precipitation rates and climatic conditions; and ha to similar precipitation rates and climatic conditions; and have 

drainage areas with similar soils, rechar drainage areas with similar soils, recharge patterns, channel ge patterns, channel 

patterns, and ph patterns, and physiographic characteristics. Deri ysiographic characteristics. Deriving channel- ving channelgeometry equations from streams within a gi geometry equations from streams within a given hydrologic ydrologic 

region can minimize v gion can minimize variance in each v ariance in each variable and increase the ariable and increase the 

accuracy of the equations. y of the equations. 

The New York State Hydrologic and Habitat ork State Hydrologic and Habitat 

Modification (HHM) subcommittee of the Ne ication (HHM) subcommittee of the New York State ork State 

Nonpoint-Source Coordinating Committee (NSCC) is 

overseeing a state erseeing a statewide cooperati wide cooperative effort to defort to develop such elop such 

equations using a protocol de equations using a protocol developed by the Ne eloped by the New York City ork City 

Department of En Department of Environmental Protection Stream Management vironmental Protection Stream Management 

Program (NYCDEP-SMP; Miller and Da Program (NYCDEP-SMP; Miller and Davis, 2003; Po vis, 2003; Powell 

and others, 2003). Similar ef and others, 2003). Similar efforts are being conducted in forts are being conducted in 

other parts of North America, including V other parts of North America, including Vermont (Jaquith ermont (Jaquith 

and Kline, 2001), southern Ontario (Annable, 1996), and 

the Pennsylv the Pennsylvania-Maryland Piedmont area (White, 2001). ania-Maryland Piedmont area (White, 2001). 

These equations, which reflect localized precipitation rates, 

hydrologic conditions, ph ydrologic conditions, physiographic characteristics, and ysiographic characteristics, and 

soil properties, are e soil properties, are expected to pro xpected to provide more reliable results vide more reliable results 

than the currently a than the currently available channel-geometry equations that ailable channel-geometry equations that 

represent widespread geographic re represent widespread geographic regions, such as the eastern gions, such as the eastern 

United States (Dunne and Leopold, 1978).

Approach

In 2001, the U.S. Geological Surv In 2001, the U.S. Geological Survey (USGS), in y (USGS), in 

cooperation with the Ne cooperation with the New York State Department of ork State Department of 

Environmental Conserv vironmental Conservation (NYS DEC), and the Ne ation (NYS DEC), and the New 

York State Department of T ork State Department of Transportation (NYS DO ransportation (NYS DOT), 

and with assistance from the Ne and with assistance from the New York City Department ork City Department 

of Environmental Protection (NYC DEP), the Dela vironmental Protection (NYC DEP), the Delaware 

County Soil and W County Soil and Water Conserv ater Conservation District (DCSWCD) ation District (DCSWCD) 

and the Greene County Soil and W and the Greene County Soil and Water Conserv ater Conservation District ation District 

(GCSWCD), be (GCSWCD), began a 6-year study to def an a 6-year study to define the relations ine the relations 

between drainage-area size and channel characteristics for the 

eight hydrologic reydrologic regions of Negions of New York State (eork State (excluding Long xcluding Long 

Island) Island) (fig. 1A) that were pre that were previously established to predict viously established to predict 

flood floflood flows of unrews of unregulated streams (Lumia, 1991). Boundaries gulated streams (Lumia, 1991). Boundaries 

of the hof the hydrophysiographic re ysiographic regions from Lumia (1991) were gions from Lumia (1991) were 

used as preliminary h used as preliminary hydrologic-reydrologic-region boundaries to group gion boundaries to group 

streams with similar characteristics. Equations ha streams with similar characteristics. Equations have been 

developed for Re eloped for Regions 4 and 4a (Miller and Da gions 4 and 4a (Miller and Davis, 2003) and vis, 2003) and 

Region 5 (Wgion 5 (Westergard and others, 2005). The objecti ard and others, 2005). The objectives of 

the continuing study are to (1) complete bankfull surv the continuing study are to (1) complete bankfull surveys on 

selected streams in all eight re selected streams in all eight regions to vgions to verify and (or) redef erify and (or) redefine 

these boundaries, (2) assess all streams for k these boundaries, (2) assess all streams for key features of y features of 

the stream-classif the stream-classification system of Rosgen (1996); namely ication system of Rosgen (1996); namely, 

channel-entrenchment ratio (ratio of flood-plain width to 

bankfull-channel width), channel-width-to-depth ratio, w bankfull-channel width), channel-width-to-depth ratio, watersurface slope, channel materials, and channel sinuosity (ratio ace slope, channel materials, and channel sinuosity (ratio 

of stream length to v of stream length to valley length), and (3) assess state y length), and (3) assess statewide 

bankfull equations by grouping channel-geometry relations 

across the eight re across the eight regions by stream type in accordance with the gions by stream type in accordance with the 

Rosgen stream-classif Rosgen stream-classification system (Miller and Da ication system (Miller and Davis, 2003).vis, 2003).

Rosgen’s (1996) stream-classif s (1996) stream-classification system w ication system was created as created 

to provide consistent stream descriptions for use in e vide consistent stream descriptions for use in evaluations aluations 

of channel stability and in the design and simulation of stable 

conditions in ung conditions in ungaged stream reaches. The geomorphologic aged stream reaches. The geomorphologic 

characteristics def characteristics defined by Rosgen (1996) that correspond ined by Rosgen (1996) that correspond 

to bankfull stage were chosen for their consistenc to bankfull stage were chosen for their consistency among y among 

streams hastreams having similar ph ving similar physiographic conditions for a gi ysiographic conditions for a given 

drainage-basin size, and among streams subject to similar 

climatic conditions (Rosgen, 1994, 1996). 

Region 6 (fgion 6 (fig. 1), the fourth of the eight h ig. 1), the fourth of the eight hydrologic ydrologic 

regions to be inspected for this study gions to be inspected for this study, extends north to the xtends north to the 

southern end of the Finger Lak southern end of the Finger Lakes region and to T gion and to Tonawanda 

Creek and its trib Creek and its tributaries, south to the Ne utaries, south to the New York-Pennsylv ork-Pennsylvania 

border, west to Lak , west to Lake Erie, and east to the T e Erie, and east to the Tioughniogioughnioga and 

Chenango Ri Chenango Rivers and their trib ers and their tributaries (Lumia, 1991). Re utaries (Lumia, 1991). Region 

6 contained only 11 acti 6 contained only 11 actively gaged sites that met the selection aged sites that met the selection 

criteria; therefore, records from three inacti criteria; therefore, records from three inactive gaged sites also aged sites also 

were used in the de were used in the development of the equations. All sites were elopment of the equations. All sites were 

on unregulated streams and had at least 10 years of dischar gulated streams and had at least 10 years of discharge 

record.

The eight hThe eight hydrophysiographic re ysiographic regions used by Lumia gions used by Lumia 

(1991) were based primarily on a residual analysis of a 

statewide multiple linear re wide multiple linear regression analysis that related the gression analysis that related the 

50-year peak-dischar 50-year peak-discharge recurrence interv ge recurrence interval to the follo al to the following 

basin characteristics: drainage-area size, main-channel slope, 

percent basin storage, mean annual precipitation, percentage 

of basin coof basin covered by forest area, mean main-channel ele ered by forest area, mean main-channel elevation, 

and a basin-shape inde and a basin-shape index. The rex. The region boundaries were based gion boundaries were based 

on these residuals and re on these residuals and regional difgional differences in geological and ferences in geological and 

physiographic conditions. These boundaries will later be ysiographic conditions. These boundaries will later be 

compared with those de compared with those developed from bankfull-surv eloped from bankfull-survey data 

collected during this and other studies, and can be adjusted, if 

needed.

Purpose and Scope

This report (1) describes the methods of site selection and 

data collection and analysis; (2) presents the relations between 

 Regionalized Equations for Bankfull Discharge and Channel Characteristics of Streams in New York State: Hydrologic 

Region 6 in the Southern Tier of New York
Figure 1. Map showing hydrologic regions in New York: A. Hydrologic-region boundaries as defined by Lumia (1991). B. Locations 

of the 11 active and 3 inactive streamflow-gaging stations used in 2002-03 stream survey in Region 6. 

GENESEE

Catteraugus Creek

Conw

ango Creek

Allegheny

River

Genesee River

Canisteo

River

Chemung River

Susquehanna River

Cohocton River

Base from U.S. Geological Survey digital data

78°

43°

80° 79° 77° 76°

42°

EXPLANATION

Region boundary

County boundary

City or town

Streamflow - gaging stations

Active, continuous record

Inactive, continuous record

Active, crest stage

Inactive, crest stage

0 30 MILES

0 10 20 30 KILOMETERS

10 20

PENNSYLVANIA

NEW YORK

Base from U.S. Geological Survey digital data

Region 7

Region

5

04224807 Stony Brook Tributary at South Dansville

03010734 Ischua Creek Tributary near Machias

01530301 Cuthrie Run near Big Flats

01521596 Big Creek near Howard

03013800 Ball Creek at Stow

04216500 Little Tonawanda Creek at Linden

04233000 Cayuga Inlet near Ithaca

04232200 Catherine Creek at Montour Falls

04215000 Cayuga Creek near Lancaster

04215500 Cazenovia Creek at Ebenezer

01514801 Catatonk Creek northwest of Owego

04216875 Little Tonawanda Creek Tributary

 near Batavia

01528000 Fivemile Creek near Kanona

03013000 Conewango Creek at Waterboro

ACTIVE SITES

INACTIVE SITES

6

5

7

1

2

4

4A 3

EXPLANATION

6 HYDROLOGIC REGION IDENTIFIER

REGION BOUNDARY

New York

80° 78° 76° 74° 72°

41°

43°

0 30 60 90 120 MILES

0 30 60 90 120 KILOMETERS

PENNSYLVANIA

NEW JERSEY

LONG ISLAND

CANADA

VERMONT

MASSACHUSETTS

CONNECTICUT

ATLANTIC

OCEAN

•

ALLEGANY

6 CHAUTAUQUA

CATTERAUGUS TOMPKINS

STEUBEN CHEMUNG

TIOGA

ERIE

WYOMING

LIVINGSTON

SCHUYLER

CAYUGA

BROOME

CORTLAND

A.

B.

03013800

03013000

03010734

04215500

04215000

04216500

04216875

04224807

01521596

01528000 04232200

01530301

04233000

01514801

Introduction 
drainage area and bankfull width, depth, cross-sectional area, 

and discharge for 14 streams in Region 6, and (3) compares 

bankfull-discharge equations developed for Region 6 in this 

study with previously developed equations for Regions 4, 4a, 

and 5 in New York State and for southeastern Pennsylvania.

Methods

Fourteen sites were surveyed during the 2002-03 field 

season. The methods used to collect and analyze the data in 

this report are described in detail in Powell and others (2004) 

and summarized below. 

Site Selection

The streams were selected to cover a wide range of 

drainage-area sizes so that the resulting equations would be 

applicable to a majority of streams within the hydrologic 

region. Other selection criteria (Miller and Davis, 2003) for 

each study reach are listed below: 

• Every reach must have a USGS streamflow-gaging station 

with at least 10 consecutive years of annual peak-discharge 

data.

• Every reach must be primarily alluvial, unregulated, and 

consist of a single channel at bankfull stage.

• Every reach must contain at least two sequences of a pool 

and a riffle, or be at least 20 bankfull widths in length.

• Every reach must have readily identifiable bankfull indicators.

• Every reach must meet the minimum requirements for 

slope-area calculation of discharge (uniform channel geometry; flow contained in single, trapezoidal channel; and watersurface elevation drop between cross sections of at least 

0.50 ft (Dalrymple and Benson, 1967), so that surveyed data 

can reliably be used in hydraulic analyses and calculation of 

bankfull discharge.

• The gage must be in the reach.

• Every reach should represent a single Rosgen (1996) stream 

type, if possible.

Not all USGS gages are installed on geomorphically 

stable stream reaches because land-owner permission, access 

to the gage, and the need for the safe measurement of high 

flows often dictate where a gage is located. Thus, bridges 

or other structures in these reaches may cause localized 

channel instability near the gages. Two methods were used 

to determine channel stability at gages selected for this 

study. Active sites: channel stability was assessed through an 

inspection of the most recent analysis of discharge data for 

evidence of scour, deposition, and frequent shifting of bed 

material. Inactive sites: channel stability was assessed through 

three to five discharge measurements made during the study 

to define the stage-to-discharge relation (rating), which was 

compared with the last known rating from when the site was 

active. Appreciable discrepancy between these two ratings 

indicated channel instability.

The 14 selected sites were referred to as “calibration 

sites” because they were used to develop or calibrate the 

channel-geometry equations. Region 6 contained 30 active 

sites with 10 or more years of record, but 19 of these sites 

were determined, during site visits, to be unsuitable for gagecalibration surveys. Therefore, 3 sites that had been inactive 

for 8 to 17 years were added, to provide a total of 14 sites that 

covered a wide range of drainage-area sizes. 

Data Collection

Preliminary reconnaissance of all sites entailed 

marking bankfull indicators, cross-section locations, and 

reach boundaries. Six bankfull indicators were used: (1) 

topographic break from vertical bank to flat flood plain, (2) 

topographic break from steep slope to gentle slope, (3) change 

in vegetation (for example, from treeless to trees), (4) textural 

change in sediment, (5) scour break, or elevation below 

which no fine debris (needles, leaves, cones, seeds) occurs, 

and (6) back of point bar, lateral bar, or low bench (Castro 

and Jackson, 2001; Miller and Davis, 2003). Identification 

of bankfull indicators was complicated at some locations by 

dense vegetation, which made indicators difficult to locate, 

or by the presence of various possible indicators at differing 

elevations at a given cross section. When this was the case, 

multiple indicators were flagged, and the data-analysis 

techniques described below were used to determine which 

bankfull stage was most accurate.

The upper and lower ends of the reach, and the locations 

of cross sections, were marked with rebar driven into the 

streambank above bankfull stage on one or both banks. Three 

or four cross sections at each site were placed in riffles or runs, 

away from channel-constricting structures such as bridges and 

culverts.

The preliminary reconnaissance was followed by a 

survey of each study reach, by methods described in Powell 

and others (2004). Longitudinal-profile and cross-sectional 

surveys were conducted at each reach. The longitudinal-profile 

survey included elevation measurements of rebar marking the 

upper and lower reach limits; all bankfull indicators; and the 

thalweg and water surface at each bankfull indicator, cross 

section, and pool-riffle transition. The cross-section surveys 

included measurements of bed and bank elevations, bankfullindicator elevations, rebar that marked cross sections, and the 

flood-plain width. The reference elevation for all surveys was 

the elevation used to define the stage-to-discharge relation 

at active sites and to develop the stage-to-discharge relation 

at inactive sites. Channel-bed material throughout the reach 

was characterized through a modified Wolman pebble count 

(Harrelson and others, 1994).

 Regionalized Equations for Bankfull Discharge and Channel Characteristics of Streams in New York State: Hydrologic 

Region 6 in the Southern Tier of New York
Data Analysis

All field data were compiled for graphical analysis. 

Construction of the bankfull-elevation profile along each reach 

entailed plotting a best-fit line through the surveyed bankfullstage indicators. Multiple lines were plotted if bankfull 

indicators were present at more than one elevation, and the 

bankfull stage and associated discharge that best agreed with 

the 1.5-year bankfull recurrence interval were used.

At active sites, the bankfull stage at the gage or staff 

plate was derived as described above, and the corresponding 

bankfull discharge was taken from the most current stageto-discharge relation. At inactive sites, bankfull discharge 

was interpolated from newly developed stage-to-discharge 

relations that were extended to bankfull stage through 

Johnson’s method (Kennedy, 1984). At all sites, estimates of 

bankfull discharge were verified through a hydraulic analysis 

of the bankfull geomorphologic data collected during the 

streamflow-gaging station calibration survey, as described 

below. Additional details are given in Powell and others 

(2004).

(1) The computer program NCALC (Jarrett and Petsch, 1985) 

was used to compute Manning’s n, the roughness coefficient 

of the channel. Data required for this computation were: 

discharge from the stage-to-discharge relation, channel-bed 

and bankfull water-surface elevations at each cross section, 

and the distance along the thalweg between cross sections 

(Jarrett and Petsch, 1985). For this report, all bankfull 

water-surface elevations were taken from best-fit lines, 

rather than from surveyed bankfull indicators, to smooth 

local variations in slope that can result from intermittent 

channel controls like bedrock outcrops and debris piles.

(2) The computer program HEC-RAS (U.S. Army Corps of 

Engineer’s Hydraulic Engineering Center River Analysis 

System; Brunner, 1997) was used to determine bankfull 

discharge by calculating water-surface elevation, as follows: 

first, the reference elevation for the survey was entered as 

the starting elevation, and Manning’s n (from the NCALC 

analysis), channel-bed elevations at each cross section, the 

distance along the thalweg between cross sections, and 

various estimated discharges were input for each cross 

section; the bankfull discharge chosen for that location was 

the discharge at the water-surface elevation (calculated by 

HEC-RAS) that most closely approximated the surveyed 

bankfull water-surface elevation; and finally, the average 

of these discharges from all cross sections in the reach was 

used as the bankfull discharge for the reach. 

(3) The bankfull discharge obtained from the stage-todischarge relation was compared with the bankfull 

discharge obtained from the HEC-RAS analysis. If the two 

discharges differed by 10 percent or less, the discharge 

obtained from the stage-to-discharge relation was then used 

as the bankfull discharge and the recurrence interval of this 

discharge was calculated. If the two discharges differed by 

more than 10 percent, however, the site and reach selection, 

discharge measurements, elevations of bankfull indicators, 

and development of the stage-to-discharge relation were 

reviewed for sources of error. If no errors were found, the 

discharge that better fit the expected 1.5-year bankfull 

recurrence interval was chosen.

Preliminary data analysis of bankfull discharge at eight 

sites (Little Tonawanda Creek Tributary near Batavia, Ischua 

Creek Tributary near Machias, Ball Creek at Stow, Little 

Tonawanda Creek at Linden, Cayuga Creek near Lancaster, 

Cazenovia Creek at Ebenezer, Catatonk Creek Northwest 

of Owego, and Conewango Creek at Waterboro, fig. 1B) 

showed that the recurrence interval of bankfull discharge 

was considerably less than the anticipated minimum 

recurrence interval of 1 year. All cross sections at these 

sites were revisited in the spring of 2004, when the watersurface elevation of bankfull flow at each cross section was 

reevaluated, and the upper extent of scour lines and bankfull 

indicators on the flood plain were examined for evidence of 

recent high flows (Rosgen, 1996). The water-surface elevation 

of bankfull flow at all cross sections was then adjusted, and 

the revised data used to rerun HEC-RAS analyses. The results 

of these analyses are presented in table 1. 

Possible explanations for the initial underestimation of 

bankfull stage are: (1) more than one clearly visible bankfull 

indicator was present, (2) one bank was appreciably higher 

than the other (Gordon and others, 1992), (3) no clear break 

between the stream bank and the flood plain was evident 

(Gordon and others, 1992), and (4) bankfull indicators were 

obscured by dense vegetation. 

Regional Equations for Bankfull 

Discharge and Channel Characteristics 

of Streams

The relations between drainage-area size and bankfull 

discharge, depth, width, and cross-sectional area were 

developed for Region 6 from data from all 14 sites and are 

presented below. The period of record, drainage area, bankfull 

discharge and associated recurrence intervals, and Rosgen 

(1994) stream type for each site are summarized in table 1.

Regionalized Relation between Bankfull 

Discharge and Drainage-Area Size

The equation for streams in Region 6 (fig. 2) was: 

bankfull discharge (ft3/s) = 48.0 (drainage area, in mi2)0.842 and 

had a coefficient of determination (R2) of 0.90. The 95-percent 

confidence and prediction intervals for the equation are 

shown in figure 2. The 95-percent confidence interval denotes 

the range within which there is a 95-percent probability 

that equations derived from data collected on another set of 

Regional Equations for Bankfull Discharge and Channel Characteristics of Streams 
Table 1. Characteristics of streamflow-gaging stations surveyed in Region 6 in New York, 2002-03.

[mi2, square miles; ft3/s, cubic feet per second. Site locations are shown in fig. 1B.]

Site name and USGS

station number

Period(s) 

of record

Drainage

 area

(mi2)

Bankfull 

discharge1

(ft3/s)

Recurrence 

interval of 

bankfull 

discharge

(years)

Reach 

stream 

type2

Little Tonawanda Creek Tributary near Batavia 

(04216875)

1976-86 1.02 403 1.01 C6

Stony Brook Tributary at South Dansville 

(04224807)

1977-82, 

1984-91, 

1996-present

3.15 154 2.05 B4c

Ischua Creek Tributary near Machias 

(03010734)

1978-81, 

1983-present

5.12 903 1.03 C5,C5cCuthrie Run near Big Flats (01530301) 1976, 

1979-81,

1983-present

5.39 265 1.82 B3c

Big Creek near Howard (01521596) 1977-present 6.32 299 2.10 B4c

Ball Creek at Stow (03013800) 1955-65, 

1967-68, 

1974-present

9.06 5803 1.10 C4

Little Tonawanda Creek at Linden (04216500) 1913-68,

1970-72, 

1977-present

22.1 3503 1.02 C4

Cayuga Inlet near Ithaca (04233000) 1937-present 35.2 794 1.35 C4

Catherine Creek at Montour Falls (04232200) 1957-62,

1964-66, 

1970,

1976-77, 

1987-present

41.1 1150 2.35 C4

Fivemile Creek near Kanona (01528000) 1937-95 66.8 1330 1.82 C3

Cayuga Creek near Lancaster (04215000) 1938-68, 

1971-present

96.4 31503 1.12 C3

Cazenovia Creek at Ebenezer (04215500) 1940-present 135 64003 1.70 C4

Catatonk Creek Northwest of Owego 

(01514801)

1988-present 151 37003 1.80 C4

Conewango Creek at Waterboro (03013000) 1938-93 290 28203 1.33 C4

1

 From stage-to-discharge relation except as noted.

2

 From Rosgen (1994): B3c: low-gradient, moderately entrenched, riffle-dominated channel with cobbles, B4c: low-gradient, moderately entrenched, riffle-dominated 

channel with gravel, C3: low-gradient alluvial channel with cobbles, C4: low-gradient alluvial channel with gravel, C5: low-gradient alluvial channel with sand, C5c-: 

very low-gradient alluvial channel with sand, C6: low-gradient alluvial channel with silt and clay; channel materials from longitudinal-profile pebble count.

3

 Discharge from HEC-RAS analysis.

   Regionalized Equations for Bankfull Discharge and Channel Characteristics of Streams in New York State: Hydrologic 

Region 6 in the Southern Tier of New York
streams in the same region would fall, whereas the wider 95-

percent prediction interval in the comparison denotes the range 

within which there is a 95-percent probability that bankfull 

discharge estimated for a single stream of a given drainage 

area sampled in the region would fall. Comparing equations 

developed for other regions and their 95-percent confidence 

and prediction intervals with those developed for streams of 

Region 6 can help ascertain regional differences in stream 

characteristics. 

Bankfull Discharge Recurrence Intervals

 The recurrence interval for the estimated bankfull 

discharge of each stream was calculated from regression 

equations relating measured discharges to known recurrence 

intervals (written commun.; Richard Lumia, 1991). Previous 

investigations reported that the average recurrence interval for 

bankfull discharge is 1.5 years and typically ranges from 1 to 

2 years (Dunne and Leopold, 1978; Rosgen, 1996; Harman 

and Jennings, 1999). The bankfull-discharge recurrence 

interval obtained for streams surveyed in Region 6 ranged 

from 1.01 to 2.35 years (table 1), and averaged 1.54 years. 

Previous investigations in Regions 4 and 4a (fig. 1) estimated 

an average bankfull-discharge recurrence interval of 1.54 

years and a range of 1.2 to 2.7 years (Miller and Davis, 

2000), and those in Region 5 (fig. 1) estimated an average of 

1.51 years and a range of 1.11 to 3.40 years (Westergard and 

others, 2005). The findings for this study are not surprising, 

in that bankfull indicators were initially identified using an 

anticipated 1.5-year recurrence interval.

Stream-Channel Dimensions in Relation to 

Drainage-Area Size 

Regression equations for bankfull channel width, depth, 

and cross-sectional area for streams in Region 6 are as follows 

(fig. 3): 

bankfull width (ft) = 16.9 (drainage area, in mi2)

0.419;

bankfull depth (ft) = 1.04 (drainage area)0.244; and 

bankfull cross-sectional area (ft2) = 17.6 (drainage 

area)0.662.

Coefficients of determination (R2) for these equations 

were 0.79, 0.64, and 0.89, respectively. The high correlation 

coefficient for the equation relating drainage-area size to 

bankfull channel cross-sectional area indicates that much 

of the variation in these two variables is explained by the 

drainage-area size alone. The lower correlation coefficients for 

the equations that relate drainage-area size to bankfull channel 

width and depth, however, indicate that other factors, such as 

slope and channel materials (Leopold, 1994), could also affect 

these relations.

The raw data for Region 6 equations and the 

corresponding 95-percent confidence and prediction intervals 

are provided in plots of mean bankfull width, depth, and crosssectional area as a function of drainage-area size in figures 4A 

through 4C. 

Figure 2. Graph showing bankfull discharge (y) as a function of drainage-area size (x) for streams 

surveyed in Region 6 in New York, with 95-percent confidence and prediction intervals for all sites.

1 10 100 1,000

10

100

1,000

10,000

100,000

DRAINAGE AREA, IN SQUARE MILES

BANKFULL DISCHARGE, 

IN CUBIC FEET PER SECOND 

1

y = 48.0x

0.842

R2= 0.90 

95-percent prediction interval 

95-percent confidence interval 

Regional Equations for Bankfull Discharge and Channel Characteristics of Streams 
Stream and Reach Classification

The Rosgen classification system (Rosgen, 1996) 

categorizes streams on the basis of channel morphology 

to provide consistent, quantitative descriptions of stream 

condition (Harman and Jennings, 1999). The current study 

used the following criteria and measurements to classify 

streams; the values measured in this study are given in table 2.

•	 Entrenchment ratio: a field measurement of channel 

incision, defined as the flood-plain width divided by the 

bankfull width (Harman and Jennings, 1999). The floodplain width is measured at the elevation of twice the maximum stream depth at bankfull.

• Width-to-depth ratio: the bankfull width divided by the 

mean bankfull depth (Harman and Jennings, 1999).

• Water-surface slope: the difference between the watersurface elevation at the upstream end of a riffle and the 

water-surface elevation at the upstream end of another riffle 

at least 20 bankfull widths downstream, divided by the 

distance between the two riffles along the thalweg (Harman 

and Jennings, 1999).

• Median size (D50) of bed material: the median particle size, 

or the diameter that exceeds the diameter of 50 percent of 

all streambed particles (Harman and Jennings, 1999). D50 

values were obtained through a modified Wolman pebble 

count (Harrelson and others, 1994)

• Sinuosity: stream length divided by valley length (Harman 

and Jennings, 1999).

Each reach was classified by Rosgen stream type based 

on the average of stream channel metrics taken each at cross 

section (table 1). Each cross section was also separately 

classified by Rosgen stream type (table 2). Stream types 

“A” through “G” indicate seven major stream categories 

that differ in entrenchment, gradient, width/depth ratio, and 

sinuosity. Within each major category, the numbers 1 through 

6 are assigned to delineate dominant channel materials from 

bedrock to silt/clay along a continuum of gradient ranges 

(Rosgen, 1996). 

All cross sections were the same stream type as the entire 

reach. Most of the streams surveyed were C-type reaches; the 

rest were B-type (table 2). All of the B reaches had slopes 

less than 0.02 and, therefore, were classified as Bc reaches 

(Rosgen, 1996). 

Region 6 Equation in Relation to those 

Developed for Other Areas

 The Region 6 equation for the relation between bankfull 

discharge and drainage-area size was compared with the 

corresponding equations for three other regions in New York 

State and one in Pennsylvania (fig. 5). The apparent similarity 

Figure 3. Graph showing bankfull channel width, depth, and cross-sectional area (y) as a function of drainage-area 

size (x) for all streams surveyed in Region 6 in New York, with best-fit lines, regression equations, and coefficient of 

determination (R2) values.

y = 17.6x0.662

R2 = 0.89 

y = 16.9x0.419

R2 = 0.79 

0.1

1

10

100

1,000

0.1 1 10 100 1,000

DRAINAGE AREA, IN SQUARE MILES 

BANKFULL CHANNEL WIDTH AND DEPTH, IN FEET,

AND CROSS-SECTIONAL AREA, IN SQUARE FEET

y = 1.04x0.244

R2 = 0.64 

× × ××

×

×

×

× ×

×

×

××

× ×

×

×

×

×

×

×

×

×

×

×

×

×

××

×× ×

× ×

× × ××

× ×

×

×

Bankfull channel width

Bankfull channel depth

Bankfull channel cross-sectional area

 Regionalized Equations for Bankfull Discharge and Channel Characteristics of Streams in New York State: Hydrologic 

Region 6 in the Southern Tier of New York
Figure 4. Graph showing mean channel 

dimensions as a function of drainage-area 

size for streams in Region 6 in New York, 

with 95-percent confidence and prediction 

intervals: A. Bankfull channel width. 

B. Bankfull channel depth. C. Bankfull 

channel cross-sectional area. 

BANKFULL CHANNEL CROSS-SECTIONAL

AREA, IN SQUARE FEET

BANKFULL CHANNEL WIDTH,

IN FEET

BANKFULL CHANNEL DEPTH,

IN FEET

DRAINAGE AREA, IN SQUARE MILES

y = 16.9x0.419

R2 = 0.79

1

10

100

1,000

y = 1.04x0.244

R2 = 0.64

0.1

1

10

y = 17.6x0.662

R2 = 0.89

1

10

100

1,000

10,000

1 10 100 1,000

95-percent prediction interval

95-percent confidence interval

95-percent prediction interval

95-percent confidence interval

95-percent prediction interval

95-percent confidence interval

A. BANKFULL CHANNEL WIDTH

B. BANKFULL CHANNEL DEPTH

 C. BANKFULL CHANNEL CROSS-SECTIONAL AREA

Regional Equations for Bankfull Discharge and Channel Characteristics of Streams 
Table 2. Stream classification and bankfull channel-geometry data for cross-sections at the 14 streamflow-gaging stations surveyed in Region 6 in New York, 2002-03.

[ft, feet; ft2, square feet; mi2, square miles; mm, millimeters. Site locations are shown in fig. 1B.]

Site name and

gaging-station number

Drainage 

area

(mi2

)

Distance 

to cross 

section 

from top of 

reach (ft)

Bankfull 

width (ft)

Bankfull 

depth (ft)

Bankfull 

crosssection 

area (ft2

)

Floodplain 

width (ft)

Entrenchment

 ratio1

Widthto-depth 

ratio

Watersurface 

slope

D50

(mm)2 Sinuosity3

Crosssection

stream 

type4

Little Tonawanda Creek Tributary near Batavia(04216875)

1.02 130 36.6 0.5 18.2 210 5.7 73 .003 0.06 1.51 C6

153 16.1 1.0 15.5 98 6.1 16 .003 0.06 C6180 13.1 1.0 13.6 91 6.9 13 .003 0.06 C6

Stony Brook Tributary at South Dansville(04224807)

3.15 105 20.8 1.1 22.5 45 2.2 19 .014 37.2 1.16 B4c

125 27.2 1.1 30.2 45 1.7 25 .014 37.2 B4c143 33.7 0.9 30.5 47 1.4 37 .014 37.2 B4c

Ischua Creek Tributary near Machias(03010734)

5.12 99 35.0 1.6 55.5 370 10.6 22 .003 1.1 1.38 C5

133 37.0 2.2 79.9 364 9.8 17 .003 1.1 C5160 34.0 2.1 70.5 368 10.8 16 .003 1.1 C5686 41.5 2.0 84.4 255 6.1 21 <.001 0.2 C5c701 42.4 1.7 73.9 250 5.9 25 <.001 0.2 C5c717 37.4 2.1 78.5 245 6.6 18 <.001 0.2 C5cCuthrie Run 

near Big Flats(01530301)

5.39 501 33.2 1.6 51.9 51 1.5 21 .016 64.8 1.13 B3c

525 31.7 1.5 46.5 51 1.6 21 .016 64.8 B3c558 32.3 1.6 52.3 60 1.9 20 .016 64.8 B3c

Big Creek near Howard(01521596)

6.32 350 22.4 2.0 45.9 38 1.7 11 .012 55.9 1.09 B4c

408 23.1 2.2 51.2 37 1.6 11 .012 55.9 B4c457 27.6 2.7 74.5 36 1.3 10 .012 55.9 B4c

Ball Creek at Stow(03013800)

9.06 176 86.0 1.8 153 503 5.8 48 .002 19 1.35 C4

202 56.6 1.5 86.1 1000 17.7 38 .002 19 C4240 72.7 1.0 69.1 1000 13.8 73 .002 19 C4

Little Tonawanda Creek at Linden(04216500)

22.1 420 44.6 3.1 137 181 4.1 14 0.001 18.3 1.33 C4

489 65.0 2.4 155 152 2.3 27 0.001 18.3 C4565 56.2 2.6 148 160 2.8 22 0.001 18.3 C4

Cayuga Inlet near Ithaca(04233000)

35.2 326 61.9 3.4 213 262 4.2 18 0.004 35.2 1.63 C4

380 54.1 2.9 157 156 2.9 19 0.004 35.2 C4440 52.0 3.2 168 162 3.1 16 0.004 35.2 C4

10 Regionalized Equations for Bankfull Discharge and Channel Characteristics of Streams in New York State: Hydrologic 

Region 6 in the Southern Tier of New York
Site name and

gaging-station number

Drainage 

area

(mi2

)

Distance 

to cross 

section 

from top of 

reach (ft)

Bankfull 

width (ft)

Bankfull 

depth (ft)

Bankfull 

crosssection 

area (ft2

)

Floodplain 

width (ft) 

Entrenchment

 ratio1

Widthto-depth 

ratio

Watersurface 

slope

D50

(mm)2 Sinuosity3

Crosssection

stream 

type4

Catherine Creek at Montour Falls(04232200)

41.1 602 83.3 2.1 172 615 7.4 40 0.007 38.5 1.16 C4

666 59.1 2.9 170 160 2.7 20 0.007 38.5 C4729 43.5 2.6 111 124 2.9 17 0.007 38.5 C4983 58.0 3.0 174 192 3.3 19 0.008 42.7 C4

1038 59.2 3.3 198 140 2.4 18 0.008 42.7 C4

Fivemile Creek near Kanona(01528000)

66.8 1052 63.3 2.1 136 600 9.5 30 0.004 84.8 1.17 C3

1104 81.1 2.4 197 1500 18.5 34 0.004 84.8 C31169 64.0 2.4 157 525 8.2 27 0.004 84.8 C31241 116 1.9 219 1500 13.0 61 0.003 96.3 C31310 97.9 2.1 201 1500 15.3 47 0.003 96.3 C31363 85.2 2.5 210 1500 17.6 34 0.003 96.3 C3

Cayuga Creek near Lancaster(04215000)

96.4 1733 108 4.6 493 1100 10.2 23 0.002 89.6 1.03 C3

1858 133 3.8 484 626 4.7 35 0.002 89.6 C31972 177 3.2 572 1100 6.2 55 0.002 89.6 C3

Cazenovia Creek at Ebenezer(04215500)

135 1424 164 5.2 848 1100 6.7 31 0.001 20.7 1.52 C4

1560 146 4.9 710 1100 7.5 30 0.001 20.7 C41705 208 4.2 869 1100 5.3 49 0.001 20.7 C4

Catatonk Creek Northwest of Owego(01514801)

151 418 304 2.5 768 504 1.7 121 0.001 55.8 1.06 C4

540 247 3.0 743 506 2.1 82 0.001 55.8 C4692 245 3.3 802 512 2.1 74 0.001 55.8 C4

Conewango Creek at Waterboro(03013000)

290 142 207 2.1 426 1100 5.3 98 0.002 55.4 1.14 C4

221 130 4.0 518 800 6.2 33 0.002 55.4 C4334 122 4.0 494 1180 9.6 31 0.002 55.4 C4

1 Entrenchment ratio: floodplain width divided by bankfull width (Harman and Jennings, 1999)2 D50: median particle size, the diameter that exceeds that of 50 percent of all streambed particles at each set of cross sections3 Sinuosity: ratio of stream length to valley length (Harman and Jennings, 1999)4 From Rosgen (1994): B3c: low-gradient, moderately entrenched, riffle-dominated channel with cobbles, B4c: low-gradient, moderately entrenched, riffle-dominated channel with gravel, C3: 

low-gradient alluvial channel with cobbles, C4: low-gradient alluvial channel with gravel, C5: low-gradient alluvial channel with sand, C5c-: very low-gradient alluvial channel with sand, C6: lowgradient alluvial channel with silt and clay.

Table 2. (continued) Stream classification and bankfull channel-geometry data for cross-sections at the 14 streamflow-gaging stations surveyed in Region 6 in New York, 2002-03.

Regional Equations for Bankfull Discharge and Channel Characteristics of Streams 11
Figure 5. Graph showing bankfull discharge as a function of drainage-area size for Region 6 in New York, and published curves for 

four other regions in the Northeast. 

10

100

1,000

10,000

0.1 1 10 100 1,000

341

Region 5 (1)

Southeast Pennsylvania (2)

Region 4 (3)

Region 4a (3)

Region 6

Region 6 - 95 percent

confidence limits

5

4

4A

New York 

PENNSYLVANIA 

CANADA 

ATLANTIC 

OCEAN

LONG ISLAND 

Base from U.S. Geological Survey digital data 

ONTARIO 

78° 76° 74° 72° 

41° 

43° 

45o

BANKFULL DISCHARGE, IN CUBIC FEET PER SECOND

DRAINAGE AREA, IN SQUARE MILES 

Lake Ontario

Lake Erie 

LOCATION MAP 

Sources:

1 Westergard and others, 2005

2 Dunne and Leopold, 1978

3 Miller and Davis, 2003

80° 

EXPLANATION 

0 30 60 90 120 MILES 

0 30 60 90 120 KILOMETERS 

6

12  Regionalized Equations for Bankfull Discharge and Channel Characteristics of Streams in New York State: Hydrologic 

Region 6 in the Southern Tier of New York
among most of the curves may reflect physiographic similarity 

among the regions. The slope of the Region 6 curve is similar 

to that of the Region 5 curve (Westergard and others, 2005) 

and the southeastern Pennsylvania curve (Dunne and Leopold, 

1978). Both of these curves and the Region 4 curve (Miller 

and Davis, 2003) lie within the 95-percent confidence interval 

of the Region 6 curve. Differences are evident, however, and 

indicate a need to develop equations by region before applying 

them in local planning and design. For example, the New York 

Region 4a curve (Miller and Davis, 2003) has a much steeper 

slope than the other curves, possibly as a result of the steep 

topography in this mountainous region. This steep topography 

can cause greater bankfull flows than in flatter areas. The 

Region 4 curve, which lies above the upper bound of the 

95-percent confidence interval for Region 5, is probably also 

affected by steep topography. 

Limitations of This Study

An assumption made in this study–that the bankfull 

discharge was within the 1- to 2-year recurrence-interval 

range–may be an oversimplification (Thorne and others, 

1997), even though similar recurrence intervals have been 

estimated in other regions in New York State (Westergard 

and others, 2005; Miller and Davis, 2003) and outside New 

York State (Harman and Jennings, 1999; Rosgen, 1994). For 

example, identification of bankfull indicators during the initial 

site inspections assumed a 1- to 2-year recurrence interval, 

but if the bankfull recurrence interval at a site were longer 

or shorter than that frequency, the bankfull channel could be 

incorrectly identified (White, 2001). 

An additional limiting factor in the strength of the 

results of this study was the small number of active USGS 

streamflow-gaging stations in Region 6. Nine of the 14 sites 

surveyed had gages that measured peak flows only, and three 

had inactive gages. The lack of complete data from the peakflow-only sites required two assumptions: (1) the annual peaks 

on which recurrence-interval data are based were always at or 

above bankfull stage, and (2) the computer-generated stageto-discharge rating accurately reflected current hydrologic 

conditions. Similarly, the lack of recent data from the inactivegage sites required three assumptions: (1) the recurrence 

interval of bankfull discharge had not changed since the site 

was last active (flood-frequency analysis was performed for 

active periods of each site), (2) the channel pattern at the 

site had not been noticeably altered by floods, diversions, 

ground-water recharge, or changes in land use since the site 

was discontinued, and (3) three to five low- to medium-flow 

discharge measurements were sufficient to define a stage-todischarge relation that could reliably be extended to define a 

bankfull discharge. The violation of any of these conditions 

could result in a change in the recurrence interval of bankfull 

discharge and, subsequently, the misidentification of bankfull 

stage.

Regional channel-geometry equations can be more 

reliable than statewide equations in the design of streamrestoration projects, enhancement of fish habitat, and 

adjustment of other in-stream and riparian structures 

(Castro and Jackson, 2001) because they incorporate local 

characteristics that directly affect channel geometry. Users of 

regional equations need to recognize the limitations of these 

relations, however, and accept that they are designed only to 

provide general estimates of bankfull-channel dimensions 

and discharges (White, 2001) and do not obviate the need for 

field measurement and verification of bankfull stream-channel 

dimensions.

Summary and Conclusions

Equations relating bankfull discharge and channel 

dimensions (width, depth, and cross-sectional area) to the size 

of the drainage area at gaged streams are needed to predict 

bankfull discharge and channel dimensions at ungaged streams 

and to provide information for the design of stream-restoration 

projects. The USGS, in cooperation with the NYS DEC and 

the NYS DOT, undertook a study to develop these equations 

for streams in western New York (Region 6). Eleven active 

and 3 inactive sites were chosen according to established 

guidelines. Stream-survey data and discharge records from 

these sites were used in regression analyses to relate bankfull 

discharge and bankfull channel width, depth, and crosssectional area to the size of the drainage area. The resulting 

equations were: 

bankfull discharge (ft3/s) = 48.0 (drainage area, in mi2)0.842

bankfull channel width (ft) = 16.9 (drainage area)0.419

bankfull channel depth (ft) = 1.04 (drainage area)0.244

bankfull channel cross-sectional area (ft2) = 17.6 

(drainage area)0.662

The high coefficient of determination (R2) for the 

equations describing bankfull discharge and cross-sectional 

area (0.90 and 0.89, respectively) indicate that much of the 

variation in these variables is explained by the size of the 

drainage area. The lower correlation coefficients for bankfull 

channel width and depth (0.79 and 0.64, respectively) indicate 

that drainage-area size alone cannot be used to predict these 

variables accurately.

Recurrence intervals were calculated for the estimated 

bankfull discharge of each stream, using regression equations 

relating measured discharges to known recurrence intervals. 

The recurrence intervals for bankfull discharge of surveyed 

streams in Region 6 ranged from 1.01 to 2.35 years, with 

a mean recurrence interval of 1.54 years. Streams were 

classified by Rosgen stream type on the basis of specific 

channel characteristics at each surveyed cross-section. Most 

streams contained C-type reaches, with occasional B-type 

reaches. 

The Region 6 equation for the relation between bankfull 

discharge and drainage-area size was compared with equations 

Summary and Conclusions 13
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geometry curves: Waterbury, Vt., Vermont Water Quality Division, 

accessed March 6, 2003, at: (http://www.anr.state.vt.us/dec/waterq/

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user’s manual—verification of Manning’s Roughness Coefficient in 

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book 3, chap. A10, 59 p.

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

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geomorphology: San Francisco, W.H. Freeman, 522 p.

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unregulated streams in New York, excluding Long Island: U.S. 

Geological Survey Water-Resources Investigations Report 90-4197, 

119 p.

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relationships for bankfull discharge and hydraulic geometry at USGS 

stream gage sites in the Catskill Mountains, N.Y.: New York City 

Department of Environmental Protection Technical Report, 24 p.

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B.P , Gallagher, A. and Starr, R.R., 2004, Guidelines for surveying 

bankfull-discharge geometry and developing regional hydraulicgeometry models for streams of New York State: U.S. Geological 

Survey Open-File Report 03-92, 26 p., online only. 

Rosgen, D.L., 1994, A classification of natural rivers: Catena, v. 22, no. 

3, p. 169-199.

Rosgen, D.L., 1996, Applied river morphology: Pagosa Springs, Colo., 

Wildland Hydrology, 388 p.

Thorne, C.R., Hey, R.D., and Newson, M.D., 1997, Applied fluvial 

geomorphology for river engineering and management: Chichester, 

U.K., John Wiley and Sons, 376 p.

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, online only.

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.

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developed for four other parts of New York State and 

southeastern Pennsylvania. The differences among results 

indicate that, although similar regions have similar relations 

between bankfull discharge and channel characteristics, 

the equations need to be refined by region to improve their 

accuracy when they are applied to local planning and design 

efforts. 

Acknowledgements

Thanks are extended to Daniel Davis, Sarah Miller, and 

Elizabeth Reichheld (NYCDEP); and Rene VanSchaack, 

Douglas Dekoskie, Joel Dubois, and Jake Buchanan (Greene 

County Soil and Water Conservation District) for advice on 

geomorphology training and on survey and data analysis and 

methods of interpretation. Thanks also to Richard Lumia 

(USGS) for calculating recurrence intervals, and to Matthew 

Horn, Rebecca Pratt, and Dana Warren (Cornell University) 

for assistance in the field.

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14  Regionalized Equations for Bankfull Discharge and Channel Characteristics of Streams in New York State: Hydrologic 

Region 6 in the Southern Tier of New York