PKFQWin

Program PeakFQ provides estimates of instantaneous annual-maximum peak flows for a range of recurrence intervals, including 1.5, 2, 2.33, 5, 10, 25, 50, 100, 200, and 500 years (annual-Exceedance probabilities of 0.6667, 0.50, 0.4292 0.20, 0.10, 0.04, 0.02, 0.01, 0.005, and 0.002, respectively).
PeakFQ reads annual peaks in the WATSTORE standard format and in the Watershed Data Managaement (WDM) format. Annual peak flows are available from NWISWeb (http://nwis.waterdata.usgs.gov/usa/nwis/peak).