• The three-day mean of the 1862 flood (estimated to be 265,000 cfs) is likely the largest peak discharge on the American River since 1848 (and perhaps since the beginning of the 19th century). This historical information should be used in American River frequency analysis, although there are questions about its accuracy and about its relevance given the potential hydrologic impacts of hydraulic gold mining.
  • Although the quality of the paleoflood information developed by the U.S. Bureau of Reclamation is excellent, it has two problems. First, explicit use of this information in flood frequency requires the assumption that floods are independent and identically distributed in time or the use of a particular non-independent and identically distributed model. Existing paleoclimatic data call into question the assumption, but are not yet of sufficient quality to allow development of such models. Second, the USBR paleoflood information does not include any information about paleofloods of the magnitudes of greatest interest-discharges with exceedance probabilities from 0.5 up to and beyond 0.002. For these reasons, the use of the USBR paleoflood information was approached with caution.
  • Meyer's envelope curve of maximum flood discharges is not especially useful to American River frequency analysis.
  • The two most recent PMF estimates for the American River at Folsom Dam represent reasonable upper bounds on the three-day flood quantile associated with a probability of at most 1 x 10-3.

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