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#           Methods for estimating regional coefficient of skewness for unregulated streams in New England, based on data through water year 2011      

      September 13, 2019    

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The magnitude of annual exceedance probability floods is greatly affected by the coefficient of skewness (skew) of the annual peak flows at a streamgage. Standard flood frequency methods recommend weighting the station skew with a regional skew to better represent regional and stable conditions. This study presents an updated analysis of a regional skew for New England developed using a robust Bayesian weighted and generalized least squares regression model. Nineteen explanatory variables for 153 streamgages were tested in the regression analysis, but none were statistically significant and, as a result, a constant model was selected to define the regional skew for New England. The constant model for the New England region has, in log units, a skew of 0.37, a model error variance of 0.13, and an average variance of prediction at a new site of 0.14. An assessment of the selected regional skew model was conducted using a Monte Carlo analysis. The Monte Carlo simulations reveal that the perceived pattern in the station skews among the 153 streamgages is an artifact of the sample variability and the covariance structure of the errors.

## Citation Information

## Related Content

                  -              Data           
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June 18, 2019

####                 Peak-flow files and PeakFQ output files for U.S. Geological Survey streamgages in the New England region that were used in regional skew analysis              

Water Resources Mission Area

####             Andrea G. Veilleux, PhD (Former Employee)          

##### Civil Engineer (Hydrologic)

Water Resources Mission Area

#### Glenn Hodgkins

##### Research Hydrologist

New England Water Science Center

gahodgki@usgs.gov

207-626-6621

#### Elizabeth Ahearn

##### Hydrologist

New England Water Science Center

eaahearn@usgs.gov

860-291-6745

#### Scott A Olson

##### Hydrologist

New England Water Science Center

solson@usgs.gov

603-226-7815

## Related Content

June 18, 2019

####                 Peak-flow files and PeakFQ output files for U.S. Geological Survey streamgages in the New England region that were used in regional skew analysis              

Water Resources Mission Area

####             Andrea G. Veilleux, PhD (Former Employee)          

##### Civil Engineer (Hydrologic)

Water Resources Mission Area

#### Glenn Hodgkins

##### Research Hydrologist

New England Water Science Center

gahodgki@usgs.gov

207-626-6621

#### Elizabeth Ahearn

##### Hydrologist

New England Water Science Center

eaahearn@usgs.gov

860-291-6745

#### Scott A Olson

##### Hydrologist

New England Water Science Center

solson@usgs.gov

603-226-7815

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####             Water Resources Mission Area - Headquarters        

USGS Headquarters12201 Sunrise Valley DriveReston, VA20192United States

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