NOAA Data Website
How to Use NOAA Atlas 14 for Stormwater Design and Hydrologic Modeling
Accurate rainfall data is the foundation of reliable stormwater and hydrologic design. One of the most valuable tools available to engineers in the United States is the NOAA Precipitation Frequency Data Server (PFDS), which provides access to NOAA Atlas 14 rainfall statistics.
In this article, we’ll provide an overview of:
What NOAA Atlas 14 is
How to access rainfall frequency data
What kind of information is available
How engineers use it in hydrologic and hydraulic modeling
What Is NOAA Atlas 14?
NOAA Atlas 14 is a national dataset developed by the National Oceanic and Atmospheric Administration (NOAA) that provides precipitation frequency estimates for all 50 states and selected U.S. territories.
The Precipitation Frequency Data Server (PFDS) is a point-and-click interface that allows users to retrieve rainfall statistics for specific locations.
These precipitation frequency estimates are used to define:
Design storm depths
Recurrence intervals (2-year, 10-year, 100-year storms, etc.)
Duration-specific rainfall totals (5-minute, 1-hour, 24-hour, etc.)
Confidence intervals for rainfall estimates
For stormwater designers, this data is essential.
How the PFDS Tool Works
The NOAA PFDS interface is map-based and user-friendly.
Step 1: Select a State
Users can either click on a state on the U.S. map or select one from a drop-down menu.
Step 2: Choose a Location or Rain Gauge
Once inside a state view, you can:
Click directly on the map
Select a specific rain gauge station
Identify a precise project location
Step 3: View Rainfall Frequency Tables
After selecting a location, NOAA provides:
Tabular rainfall frequency estimates
Graphical representations
Multiple storm durations
Recurrence intervals
90% confidence intervals
The data can typically be downloaded as an Excel file for use in modeling workflows.
In many cases, you can also switch between English and metric units.
What Information Is Available?
The PFDS provides:
Intensity-Duration-Frequency (IDF) data
Storm depth tables
Confidence intervals
Supplementary rainfall statistics
Some states include additional regional resources, such as:
Short-duration rainfall relationships
Atlas volume references
Supplemental regional documentation
GIS Grids and Mapping Tools
Beyond point-based rainfall estimates, NOAA also provides:
GIS precipitation frequency grids
Cartographic maps
Statewide precipitation frequency maps
Duration- and frequency-specific mapping layers
These resources are useful for regional planning, watershed studies, and regulatory documentation.
National Weather Service Hydrologic Resources
The National Weather Service (NWS) Office of Hydrologic Development provides additional tools linked to NOAA Atlas 14, including:
Hydrologic Prediction Services
River Forecast Center (RFC) tools
Precipitation Frequency and PMP (Probable Maximum Precipitation) data
These resources support both routine stormwater design and extreme-event analysis.
How Engineers Use NOAA Rainfall Data
NOAA Atlas 14 rainfall data is commonly used for:
Defining design storms in EPA SWMM
Input parameters in TR-55 modeling
Detention and retention pond sizing
Floodplain and hydraulic studies
Regulatory submittals requiring IDF verification
Without reliable precipitation frequency data, stormwater modeling would lack statistical grounding.
NOAA provides the standardized rainfall baselines engineers depend on.
Why This Tool Matters
The NOAA PFDS tool allows engineers to:
Access decades of rainfall data instantly
Retrieve location-specific design values
Download formatted data for modeling software
Document rainfall sources in regulatory reports
It remains one of the most important public tools for stormwater and hydrologic design in the United States.
Additional Resources
At Clear Creek Solutions, we provide several free educational resources, including:
A free EPA SWMM video course (24 lessons)
A free Hydrology Tools Guide, outlining different hydrologic methodologies used across the United States
Software tutorials covering SWMM and TR-55
You can access these resources through the links on our website and YouTube channel.
