Regionalized Equations for Bankfull-Discharge and Channel Characteristics of Streams
in New York State: Hydrologic Region 5 in Central New York
by Britt E. Westergard, Christiane I. Mulvihill, Anne G. Ernst, and Barry P. Baldigo
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2004-5247
ABSTRACT
Equations that relate drainage area to bankfull discharge
and channel dimensions (width, depth, and cross-sectional
area) at gaged sites are needed to define bankfull discharge
and channel dimensions at ungaged sites and to provide
information for 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. A study
to develop equations to predict bankfull data for ungaged
streams in New York established eight regions that coincided
with previously defined hydrologic regions. This report
presents drainage areas and bankfull characteristics (discharge
and channel dimensions) for streams in central New York
(Region 5) selected for this pilot study.
Stream-survey data and discharge records from seven
active (currently gaged) sites and nine inactive (discontinued
gaged) sites were used in regression analyses to relate size
of drainage area (mi2) to bankfull discharge and bankfull channel
width, depth, and cross-sectional area. The resulting equations
are:
bankfull discharge = 45.3*(drainage area)0.856;
bankfull channel width = 13.5*(drainage area)0.449;
bankfull channel depth = 0.801*(drainage area)0.373;
bankfull channel cross-sectional area = 10.8*(drainage area)0.823.
The high correlation coefficients (R2) for these four equations (0.96, 0.92, 0.91,
0.98, respectively) indicate that much of the variation in
the variables is explained by the size of the drainage area.
Recurrence intervals for the estimated bankfull discharge
of each stream ranged from 1.11 to 3.40 years; the mean
recurrence interval was 1.51 years. The 16 surveyed streams
were classified by Rosgen stream type; most were mainly
C-type reaches, with occasional B- and F-type reaches. The
Region 5 equation was compared with equations developed for
six other large areas in the Northeast. The major differences
among results indicate a need to refine equations so they can
be applied by water-resources managers to local planning and
design efforts.
Citation: 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.
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