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USGS New York Spatial Datasets

 

Title: Flood Frequency Hydrologic Regions for New York, Excluding Long Island

 

Description: The initial step in delineating hydrologic regions was to develop a statewide regression equation through OLS (Ordinary Least-Squares) method. The response variable was the 50-year peak discharge, and the five most significant explanatory variables for the statewide equation were found to be drainage area, main-channel slope, basin storage, mean annual runoff, and water equivalent of snow cover.

 

Regression analysis provides a means of relating peak discharge to basin characteristics. Variability of the relation between peak discharge and basin characteristics among gaged sites can be reduced by regionalization, a process in which an area is divided into hydrologic regions to account for regional differences in peak-discharge response and in topographic and climatic variables that affect streamflow.  Hydrologic regions refer to areas in which streamflow-gaging stations indicate a similarity of peak-discharge response that differs from the peak-discharge response in adjacent regions.  These similarities and differences are defined by the regression residuals, which are the differences between the peak discharges calculated from station records (log-Pearson type III estimates) and the values computed through the regression equations.

 

Six hydrologic regions within New York were identified and delineated primarily through inspection of the areal distribution of the statewide regression residuals. Areas where the regression equation consistently overestimated or underestimated the peak-discharge response were delineated as discrete hydrologic regions, and separate GLS (Generalized Least-Squares) regression equations were developed to estimate peak-discharge frequencies for each region. Regional differences in geologic and physiographic conditions were also considered during the delineation; generally, the hydrologic-region boundaries were delineated to coincide with drainage-basin divides and are shown in U.S. Geological Survey Scientific Investigations Report 2006-5112.

 

The shapefile depicts the six hydrologic regions for New York.

 

View the Metadata Flood Frequency Hydrologic Regions Metadata

 

Download the Data Flood Frequency Hydrologic Regions Dataset

 

Supporting Documentation:

 USGS Scientific Investigations Report 2006-5112: Floods in New York 

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