Return period adjustment for runoff coefficients based on analysis in undeveloped Texas watersheds

Nirajan Dhakal, Xing Fang, William H. Asquith, Theodore G. Cleveland, David B. Thompson

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

The rational method for peak discharge (Qp) estimation was introduced in the 1880s. The runoff coefficient (C) is a key parameter for the rational method that has an implicit meaning of rate proportionality, and the C has been declared a function of the annual return period by various researchers. Rate-based runoff coefficients as a function of the return period, CT, were determined for36 undeveloped watersheds in Texas using peak discharge frequency from previously published regional regression equations and rainfall intensity frequency for return periods T of 2, 5, 10, 25, 50, and 100 years. The CT values and return period adjustments CT=CT 1/4 10 year determined in this study are most applicable to undeveloped watersheds. The return period adjustments determined for the Texas watersheds in this study and those extracted from prior studies of non-Texas data exceed values from well-known literature such as design manuals and textbooks. Most importantly, the return period adjustments exceed values currently recognized in Texas Department of Transportation design guidance when T > 10 years.

Original languageEnglish
Pages (from-to)476-482
Number of pages7
JournalJournal of Irrigation and Drainage Engineering
Volume139
Issue number6
DOIs
StatePublished - 2013

Keywords

  • Peak discharge
  • Rational method
  • Return period
  • Runoff coefficient

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