A history of rain-on-snow floods in the Sierra Nevada

The largest floods on record in Sierra Nevada rivers have resulted from rainfall extending into the snowpack zone. Several large rain-on-snow floods have been documented in the 19th century that allow us to estimate that 16 regional floods exceeding the general magnitude of the largest floods of the past decade have occurred in the past two years. Although some of these events have been much larger than others in particular river basins, rain-on-snow floods with the potential to cause serious damage throughout the Sierra Nevada may recur, on the average, about once per decade. Floods with a ten year recurrence interval tend to be about twice as large as the mean annual flood in most Sierra Nevada rivers. There were no obvious trends in flood magnitude or frequency over the period of record.