Regionalized equations for bankfull discharge and channel characteristics of streams in New York State — Hydrologic Regions 1 and 2 in the Adirondack Region of northern New York

Abstract

For additional information, contact: Director, New York Water Science Center U.S. Geological Survey 425 Jordan Rd Troy, NY 12180 (518) 285-5695 http://ny.water.usgs.gov/ Equations that relate drainage area to bankfull discharge and channel characteristics (width, depth, and cross-sectional area) at gaged sites are needed to define bankfull-discharge and channel characteristics at ungaged sites and to provide information for watershed assessments, stream-channel classification, and 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.Stream-survey and discharge data from 15 active (currently gaged in 2005) streamflow-gaging stations and 1 inactive (discontinued) streamflow-gaging station in hydrologic Regions 1 and 2 were used in linear-regression analyses to relate drainage area to bankfull discharge and bankfull-channel width, depth, and cross-sectional area. The four resulting equations are the following:(1) bankfull discharge, in cubic feet per second = 49.6*(drainage area, in square miles)0.849;(2) bankfull channel width, in feet = 21.5*(drainage, in square miles)0.362;(3) bankfull channel depth, in feet = 1.06*(drainage area, in square miles)0.329; and(4) bankfull channel cross-sectional area, in square feet = 22.3*(drainage area, in square miles)0.694.The coefficients of determination (R2) for these four equations are 0.95, 0.89, 0.89, and 0.97, respectively. The high coefficients of determination for these equations indicate that much variability is explained by drainage area. Recurrence intervals for the estimated bankfull discharge of each stream ranged from 1.01 to 3.80 years; the mean recurrence interval was 2.13 years. The 16 surveyed streams were classified by Rosgen stream type; most were B- and C-type, with a few E- and F-type cross sections.The hydrologic Regions 1 and 2 equation for the relation between bankfull discharge and drainage area was graphically compared to curves developed for 5 other hydrologic regions in New York State. The 95-percent confidence interval for the hydrologic Regions 1 and 2 curve fully encompassed the curves for Regions 4a, 5, and 6, showing that there are very few differences in the relation between drainage area and bankfull discharge in these four regions. However, the curves for Regions 4 and 7 lay outside the 95 percent confidence intervals of the Region 3 curve, indicating that these 3 regions do not have similar bankfull-discharge to drainage area relations.