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Competency Area 6: Watershed hydrology AEM

PO 60. Understand precipitation return periods and define a 25-year, 24-hour precipitation event and list sources for identifying this event in various parts of the Northeast.

Precipitation return periods were discussed in CA 1, PO 10. The following figure shows contour lines of the 25-year, 24-hour precipitation amounts for the Northeast (note precipitation amounts in inches on the right hand side of the contour lines). The 25-year, 24-hour precipitation amount varies between 4 to 5 inches for much of the Northeast, and increases to 6 inches for Long Island, NY, and southern areas of Connecticut. Information for many different frequency-duration storms can be obtained via the National Oceanic Atmospheric Administration (NOAA) web site