NOAA’s flood map now reaches nearly every American and 3.3 million river miles

NOAA says its Flood Inundation Mapping service, known as FIM, now reaches nearly 100 percent of the U.S. population and depicts potential flooding along 3.3 million river miles. The agency announced the expansion on September 24, 2026, raising coverage from 60 percent in 2025. Both figures are NOAA’s own description of its own product.

The wording matters, because “nearly every American” is a statement about people, not geography. The percentage counts residents living where the service now draws maps, and four areas still fall outside it.

NOAA’s Population Claim and the 3.3 Million River Miles

In its September 24 news release, NOAA describes the tool as developed by the National Weather Service and its Office of Water Prediction. The release says the maps now cover “nearly 100% of the U.S. population” and 3.3 million river miles across the continental United States, the territories and Hawaii. NOAA Administrator Neil Jacobs put the point in terms of people, saying the expansion means nearly every American can reach detailed information beyond the expected river crest height.

The river-mile figure and the population figure measure different things. One counts stretches of stream and river that the mapping service can model; the other counts residents who live inside the footprint. A region with few people but many river miles adds to the first number and barely moves the second.

The same release credits the latest expansion with new maps for the southeastern coast, Florida, the Great Lakes region, New England, the Rocky Mountains, the Dakotas and western Nebraska. Insurance Journal’s account of the announcement repeats the same 3.3 million figure and the same list of newly covered regions, and describes the maps as a way for forecasters and emergency managers to communicate neighborhood-level risk from rivers and streams. The trade publication also notes that the system works from river flow forecasts and current conditions, and that the maps are publicly accessible through the National Water Prediction Service in multiple formats, so the same layers that brief emergency managers are open to any resident who looks them up.

Because the release names both the agency and the product, the claim is traceable to one office. It is NOAA reporting on NOAA, and no outside audit of the coverage percentage appears in any of the documents reviewed. Readers weighing the figure should treat it as the agency’s own accounting of where its service now operates, which is a meaningful operational milestone but not an independent measurement of how many people can actually find and use a map for their street.

Four Inundation Products and Their Update Clocks

FIM is not one map but a family of them. The National Weather Service’s rollout flyer lists four inundation products: a five-day maximum forecast built from River Forecast Center predictions, triggered when a river reaches action stage; a 48-hour maximum forecast from the National Water Model, refreshed twice a day; a five-day National Water Model maximum forecast, refreshed every six hours; and a latest-analysis snapshot based on observations, refreshed hourly.

An earlier NWS fact sheet describes the service as geo-referenced visualizations of forecast flooding extent at continental scale, translating streamflow forecasts into maps of where water may reach.

National Weather Service Director Ken Graham said in the release that FIM “has been a game changer when briefing emergency managers.” The maps are published through NOAA’s National Water Prediction Service, whose front page carries the September 24 update announcing coverage of nearly the entire country.

The earliest phase was regional. The 2023 fact sheet says the service began by serving 10 percent of the population in select areas of Texas, the Mid-Atlantic and the Northeast, with plans to reach nearly 100 percent between 2024 and 2026. The 2024 flyer then listed the Mid-Atlantic, Northeast, Ohio, Tennessee and Mississippi valleys, Pacific Northwest, Puerto Rico and U.S. Virgin Islands among areas with operational FIM, so the September 2026 announcement completes a schedule NOAA had been publishing for three years.

Alaska and the Pacific Territories Still Missing

NOAA is explicit that coverage is incomplete. The release says the service does not yet reach northern and western Alaska, Guam, the Northern Mariana Islands or American Samoa. Those four gaps are the reason the agency says “nearly” 100 percent rather than all of it, and they also explain why the 3.3 million river-mile total is described as spanning the continental United States, the territories that are covered, and Hawaii rather than every U.S. waterway.

The trajectory is documented in NOAA’s own materials, and each step of it can be checked against a dated document rather than a retrospective summary, which is useful when a headline number moves from 10 to 60 to nearly 100 percent in three years. The service launched in 2023 serving 10 percent of the population, according to the release, and the 2024 flyer projected operational FIM for 30 percent of the population that year and nearly 100 percent in 2026. NOAA reports 60 percent in 2025, then the jump to nearly all in the September announcement. Carrier Management reported the same sequence of 10, 60 and nearly 100 percent the day after the release.

What the maps do not change is the forecast underneath them. A modeled inundation layer is only as good as the river forecast feeding it. Whether the Alaska and Pacific gaps close, and on what schedule, is not stated in the September 24 announcement.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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