Global Changes in 20-Year, 50-Year, and 100-Year River Floods

L. Slater, G. Villarini, S. Archfield, D. Faulkner, R. Lamb, A. Khouakhi, J. Yin

Research output: Contribution to journalArticlepeer-review

70 Scopus citations


Concepts like the 100-year flood event can be misleading if they are not updated to reflect significant changes over time. Here, we model observed annual maximum daily streamflow using a nonstationary approach to provide the first global picture of changes in: (a) the magnitudes of the 20-, 50-, and 100-year floods (i.e., flows of a given exceedance probability in each year); (b) the return periods of the 20-, 50-, and 100-year floods, as assessed in 1970 (i.e., flows of a fixed magnitude); and (c) corresponding flood probabilities. Empirically, we find the 20-/50-year floods have mostly increased in temperate climate zones, but decreased in arid, tropical, polar, and cold zones. In contrast, 100-year floods have mostly decreased in arid/temperate zones and exhibit mixed trends in cold zones, but results are influenced by the small number of stations with long records, and highlight the need for continued updating of hazard assessments.

Original languageEnglish (US)
Article numbere2020GL091824
JournalGeophysical Research Letters
Issue number6
StatePublished - Mar 28 2021
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • General Earth and Planetary Sciences


  • floods
  • global
  • hazard
  • nonstationarity
  • probabilities
  • return periods


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