Are FEMA flood maps accurate?

Tue Jan 11 2022

A middle class suburban Miami neighborhood shot from an altitude of approximately 700 feet

The Federal Emergency Management Agency (FEMA) developed flood maps to help communities better understand the risk of flooding in their communities. For decades, FEMA flood maps were the basis for flood regulations, building standards, and, until recently, National Flood Insurance Programs (NFIP) flood insurance rates.

FEMA’s recently implemented Risk Rating 2.0 to update its methodology for pricing NFIP policies and deliver rates that actually reflect a property’s true risk. While its Flood Insurance Rate Maps (FIRMs) are no longer the most significant factor in rating premiums, they are still used to determine which properties must have flood insurance.

And that can be a real problem. FEMA’s maps are outdated and don’t reflect the impact of climate change, which is making more and more homes vulnerable to flooding. That could create a false sense of security for homeowners outside of FEMA-designated high-risk flood areas that aren’t required to have flood insurance.

In other words: it may be part of the reason so many homeowners are utterly unprepared for a flood.

FEMA flood maps fail to reflect climate change

FEMA flood maps are supposed to show how likely an area is to flood. Areas that FEMA predicts to have more than a one-percent chance of flooding in a year are considered high-risk flood zones. These areas typically have flood insurance purchase requirements as well as building regulations to minimize damage.

FEMA bases its predictions and designations partly on historical data. That would be perfectly fine except it doesn’t reflect the impact of climate change, which means it doesn’t account for:

  • Higher water levels.
  • More intense precipitation.
  • More frequent hurricanes.

The New York Times reports that new calculations from the First Street Foundation estimates that at least 14.6 million properties across the US are at risk for flooding, compared to the 8.7 million FEMA flood maps show.

That’s a lot of properties that may have more flood risk than anyone realizes. In Chicago alone, First Street’s data shows over 75,000 properties with flood risk that have gone unrecognized on FEMA flood maps.

FEMA flood maps are often outdated or incomplete

Originally, predicting the impact of climate change wasn’t an exact science, but models are getting more accurate every year. However, not accounting for climate change is only one of the problems with FEMA flood maps. The maps are also:

  • Badly outdated. According to the National Resources Defense Council, two-thirds of FEMA flood maps haven’t been updated in five years, a cadence that’s required by federal law. Some haven’t been updated in more than 30 years.
  • Incomplete. Scientific American reports that only one-third of streams and 46 percent of coasts have been mapped by FEMA. Moreover, when data for an area isn’t updated at the five-year mark, the flood risk is considered “unknown.”

Flood risk is constantly evolving, so flood maps need to be updated regularly to incorporate new flood information and risks. But the cost (between $3.2 billion and $11.8 billion makes regular updates nearly impossible. This forces FEMA to focus on more populous areas with more risk.

The impact of FEMA flood map issues

The outcome of having outdated and incomplete flood maps is that people don’t know the risks they face. As a result, they may:

  • Unknowingly move to areas with a high risk for flood.
  • End up underinsured when a flood hits.
  • Build homes that can’t withstand flooding.

An unprepared community can also mismanage its resources. Take for example the record-breaking downpours in Tennessee in August 2021. Not only were few homeowners covered by the NFIP, but officials were unprepared for the floods that followed 17 inches of rain.

The opposite can happen, too, as it did with Hurricane Ida. FEMA predicted a storm surge of up to nine feet in Houma, Louisiana. But because flood maps weren’t updated to account for the city’s 13-foot levee system, the city used valuable resources to guard against flooding that never happened.

Building better flood maps

Put simply, flood maps need to accurately reflect today’s risk. The first step is to include climate change data, much like First Street’s Risk Factor does. It’s an interactive website where homeowners can enter their address to see what their risk is based on current and historical data that incorporates the location’s chance for:

  • High-intensity rainfall.
  • Overflow from rivers and streams.
  • Coastal storm surge.
  • High tides.

The Association of State Floodplain Managers also recommends flood maps for all populated areas as well as those with potential for population growth. As flood maps are updated, they need to account for any measures taken to reduce flood risk, such as levees and dams.

As mentioned earlier, it’s not an inexpensive undertaking to develop these maps. But catastrophic floods are even costlier. Plus, as the association notes, accurate flood maps keep people from building in risky areas so fewer homes suffer the direct cost of flood damage. Most importantly, accurate flood maps could help keep more people safe.

Homeowners also need to know that there’s really no such thing as a flood-free zone. In fact, FEMA makes a regular point of noting that 25 percent of flood claims come from areas with low-to-moderate risk. And that means flood insurance is for everyone.


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