NOV 2017
CTP Webinar: Flood Frequency Computations Using Bulletin 17C
Locations: CTP Information Exchange Webinar
Time: Thursday, Nov 16, 2017, 12:00 PM - Thursday, Nov 16, 2017, 1:00 PM

The Advisory Committee on Water Information,  Subcommittee on Hydrology, now recommends new guidelines (loosely referred to as Bulletin 17C) for flood-frequency computations.  Learn about the guidelines and hear about a case study of their general application to the Colorado River.

Bulletin 17C incorporates changes motivated by four of the items listed as “Future Work” in Bulletin 17B and 30 years of post-17B research on flood processes and statistical methods.  The updates include:

  • adoption of a generalized representation of flood data that allows for interval and censored data types;
  • a new method, called the Expected Moments Algorithm (Cohnet al., 1997, 2001), that extends the method of moments so that it can accommodate interval data;
  • a generalized approach to identification of low outliers in flood data (Cohnet al., 2013);
  • and an improved method for computing confidence intervals.

Bulletin 17C provides intensive information on data sources and selection, including nontraditional sources such as paleoflood records and rainfall-runoff simulation, record extension through correlation techniques, and flood accounts given in newspapers, journal articles and other informal media to supplement traditional peak-flow data published by the U.S. Geological Survey.

Bulletin 17C was published by the USGS on March 29, 2018. and represents a major contribution to flood frequency methods in the US.

The final version of Bulletin 17C is available at


  • Andrea Veilleux, PhD, U.S. Geological Survey
  • Brad Bettag, PE, AMEC Foster Wheeler


  • Bulletin 17C -New Guidelines for Flood-Frequency Computations
  • Application of Bulletin 17C to the Colorado River

Bulletin 17C CTP Webinar Slides

Bulletin 17C CTP Webinar Recording

Bulletin 17C Webinar Questions and Answers


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