Scientific Investigations Report 2009–5144
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.
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.
First posted October 1, 2009
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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/.
Calculating Bankfull Discharge
Bankfull Discharge and Channel Characteristics of Streams in New York State
Bankfull-Discharge Recurrence Intervals
New Hydrologic Regions
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
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