NOAA’s New Flood Mapping Tool: A Powerful Resource—but Not a Replacement for Site-Specific Floodplain Work

Flooding does not always stop neatly at a line on a map.

On September 24, 2026, the National Oceanic and Atmospheric Administration (NOAA) announced a major expansion of its experimental Flood Inundation Mapping, or FIM, system. The tool, which previously covered approximately 60% of the country, is now available to nearly 100% of the U.S. population.

Unlike a traditional river gauge that tells users how high the water is expected to rise at a particular location, Flood Inundation Mapping helps visualize where that water may actually go.

NOAA’s system combines current conditions and modeled river flows to estimate the land area that could be covered by water. Depending on location, users can see current conditions as well as forecasts extending several days into the future.

That could be an extremely valuable tool for emergency managers, communities, property owners, engineers and anyone trying to better understand an approaching flood.

But there is an important distinction.

Flood Forecasting and Floodplain Mapping Are Not the Same Thing

A forecast showing where water may travel during an upcoming flood does not replace FEMA floodplain mapping, an Elevation Certificate, a property survey, engineering analysis or a Letter of Map Revision.

Each serves a different purpose.

Flood inundation mapping helps answer a question such as:

“Where could the water go during this particular event?”

A FEMA Flood Insurance Rate Map addresses regulatory floodplain designations. An Elevation Certificate documents elevations for a particular structure or property. A CLOMR or LOMR involves engineering and surveying information used to evaluate or officially revise how a property or project is represented on FEMA's maps.

For property owners and developers, those distinctions matter.

A parcel may be near a mapped floodplain without a structure actually sitting at the same elevation as the surrounding property. Conversely, being outside a mapped Special Flood Hazard Area does not mean a site can never experience flooding.

Drainage patterns, topography, finished-floor elevations, culverts, streams, detention facilities and changes to surrounding development can all affect how water moves across a site.

Better Information Leads to Better Planning

NOAA’s expanded system is another example of how geospatial information is becoming more accessible and useful.

For the public, that can mean better situational awareness during a storm.

For engineers and surveyors, it provides another source of information that can be considered alongside field measurements, topographic surveys, drainage studies and regulatory mapping.

And for property owners and developers, it reinforces an important principle: maps are powerful tools, but understanding an individual property often requires looking beyond a single map.

At Abbie Jones Consulting, PSC, our surveying and civil engineering teams work with property owners, developers and communities on elevation surveys, floodplain issues, drainage, stormwater design and other site-specific questions.

When it comes to water, knowing not only where your property is located, but also how water moves across it, can make all the difference.

Source: NOAA, “NOAA’s Flood Mapping Tool Now Covers Nearly 100% of U.S.,” September 24, 2026.