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HydroCAD Stormwater Modeling - Since 1986

NOAA Atlas 14

What is Atlas 14?

NOAA Atlas 14 contains the latest rainfall data for much of the United States, and generally replaces the older data published in NWS Technical Paper 40 (TP-40).

How do I use Atlas 14?

If your stormwater regulations require the use of Atlas 14 data, you need to examine the regulations very carefully to determine exactly how the data should be used.  There are several alterative ways to "use Atlas 14", so you need to be clear about your requirements before you can properly setup your model.

Note: These alternatives apply specifically to the SCS/NRCS runoff procedure.  If you're using the Rational method there are fewer options to navigate, and you can generally skip ahead to download local PFD data.

Alternative A - This alternative uses the county-level 24-hour precipitation depths from Atlas 14 in conjunction with one of the predefined rainfall distributions.  In most cases you can automatically create your events using one of the pre-defined lookup tables, or you can create your events manually by entering the rainfall depth for each event.

Alternative B - This approach uses site-specific rainfall data downloaded from NOAA or other sources.  In addition to using a more precise 24-rainfall depth, you can generate a custom synthetic rainfall distribution instead of using one of the pre-defined rainfall distributions employed in Alternate A.  This is the most complete implementation of the latest rainfall data, in that you're using site-specific rainfall distributions and rainfall depths.  Details here.

For further information read about rainfall setup options.

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