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Scientific Investigations Report 2009–5144

Prepared in cooperation with
New York State Department of Environmental Conservation
New York Department of State
New York State Department of Transportation
New York City Department of Environmental Protection

Bankfull Discharge and Channel Characteristics of Streams in New York State

By Christiane I. Mulvihill,1 Barry P. Baldigo,1 Sarah J. Miller,2 Douglas DeKoskie,3 and Joel DuBois4

1 U.S. Geological Survey, 425 Jordan Rd., Troy, NY, 12180.
2 U.S. Army Engineer Research and Development Center, 3909 Halls Ferry Rd., Vicksburg, MS 39180-6199.
3 Integrated River Solutions, Inc., 9 River Rd., Ulster Park, NY 12487.
4 Greene County Soil & Water Conservation District, 907 County Office Building, Cairo, NY 12413.

ABSTRACT

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Equations that relate drainage area to bankfull discharge and channel characteristics (such as width, depth, and cross-sectional area) at gaged sites are needed to help define bankfull discharge and channel characteristics at ungaged sites and can be used in stream-restoration and protection projects, stream-channel classification, and channel assessments. These equations are intended to serve as a guide for streams in areas of similar hydrologic, climatic, and physiographic conditions. New York State contains eight hydrologic regions that were previously delineated on the basis of high-flow (flood) characteristics. This report seeks to increase understanding of the factors affecting bankfull discharge and channel characteristics to drainage-area size relations in New York State by providing an in-depth analysis of seven previously published regional bankfull-discharge and channel-characteristics curves.

Stream-survey data and discharge records from 281 cross sections at 82 streamflow-gaging stations were used in regression analyses to relate drainage area to bankfull discharge and bankfull-channel width, depth, and cross-sectional area. The R2 and standard errors of estimate of each regional equation were compared to the R2 and standard errors of estimate for the statewide (pooled) model to determine if regionalizing data reduced model variability. It was found that regional models typically yield less variable results than those obtained using pooled statewide equations, which indicates statistically significant regional differences in bankfull-discharge and channel-characteristics relations.

All but two of the bankfull-discharge curves are within the 95-percent confidence interval bands of the statewide model; all the models have statistically similar slopes, and only one model has a unique intercept. Regional variations in channel-characteristics models of bankfull width, depth, and cross-sectional area were more prevalent than for bankfull discharge, though the magnitude of the differences varied.

It was hypothesized that some regional variability could be reduced by creating models for streams with similar physiographic and climatic characteristics. Available data on streamflow patterns and previous regional-curve research suggested that mean annual runoff, Rosgen stream type, and slope were the variables most likely to influence regional bankfull discharge and channel characteristics to drainage-area size relations. Results showed that although all of these factors had an influence on regional relations, most stratified models have lower R2 values and higher standard errors of estimate than the regional models.

The New York statewide (pooled) bankfull-discharge equation and equations for regions 4 and 7 were compared with equations for four other regions in the Northeast to evaluate region-to-region differences, and assess the ability of individual curves to produce results more accurate than those that would be obtained from one model of the northeastern United States. Results indicated that model slopes lack significant differences, though intercepts are significantly different. Comparison of bankfull-discharge estimates using different models shows that results could vary by as much as 100 percent depending on which model was used and indicated that regionalization improved model accuracy.

Revised March 24, 2011

First posted October 1, 2009

For additional information contact:
Director
U.S. Geological Survey
New York Water Science Center
425 Jordan Road
Troy, NY 12180
(518)285-5600

http://ny.water.usgs.gov

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Suggested citation:

Mulvihill, C.I., Baldigo, B.P., Miller, S.J., DeKoskie, Douglas, and DuBois, Joel, 2009, Bankfull discharge and channel characteristics of streams in New York State: U.S. Geological Survey Scientific Investigations Report 2009–5144, 51 p., at http://pubs.usgs.gov/sir/2009/5144/.



Contents

Abstract

Introduction

Methods

Hydrologic-Region Delineation

Site Selection

Data Collection

Data Analysis

Calculating Bankfull Discharge

Comparing Models

Bankfull Discharge and Channel Characteristics of Streams in New York State

Bankfull-Discharge Recurrence Intervals

Bankfull Discharge

Bankfull-Channel Characteristics

Width

Depth

Cross-Sectional Area

New Hydrologic Regions

Data Stratification

Stratifying by Mean Annual Runoff

Stratifying by Rosgen Stream Type

Stratifying by Slope

Comparison of New York State Equations to those Developed for Other Regions in the Northeast

Other Uses of Regional Curves

Limitations of Regional Curves

Summary

Acknowledgments

References Cited

Appendix 1. Characteristics of Streamflow-Gaging Stations Surveyed in New York State, 1999–2006

Appendix 2. Stream Classification and Bankfull-Channel Characteristics for Streamflow-Gaging Stations Surveyed in New York State, 1999–2006



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