The lethal flooding in Texas on July 4, 2025, and damaging flash floods every week later in states together with New Mexico, Vermont and Iowa are elevating questions in regards to the nation’s flood maps and their capability to make sure that communities and householders can put together for rising dangers.
The U.S. Federal Emergency Administration Company’s flood maps are supposed to be the nation’s main instrument for figuring out flood dangers. Initially developed within the Seventies to help the Nationwide Flood Insurance coverage Program, these maps, often known as Flood Insurance coverage Price Maps, or FIRMs, are used to find out the place flood insurance coverage is required for federally backed mortgages, to tell native constructing codes and land-use choices, and to information flood plain administration methods.
In concept, the maps allow householders, companies and native officers to know their flood danger and take acceptable steps to organize and mitigate potential losses.
A federal flood map of Kerrville, Texas, with the Guadalupe River winding via the center in purple, exhibits areas thought of to have a 1% annual likelihood of flooding in blue and a 0.2% annual likelihood of flooding in tan. Throughout a flash flood on July 4, 2025, the river rose greater than 30 toes at Kerrville.
FEMA
However whereas FEMA has improved the accuracy and accessibility of the maps over time with higher information, digital instruments and neighborhood enter, the maps nonetheless don’t seize the whole lot – together with the altering local weather. There are areas of the nation that flood, some recurrently, that don’t present up on the maps as in danger.
I research flood-risk mapping as a university-based researcher and at First Road, a corporation created to quantify and talk local weather danger. In a 2023 evaluation utilizing newly modeled flood zones with climate-adjusted precipitation information, we discovered that greater than twice as many properties throughout the nation have been susceptible to a 100-year flood than the FEMA maps recognized.
Even in locations the place the FEMA maps recognized a flood danger, we discovered that the federal mapping course of, its overreliance on historic information, and political affect over the updating of maps can result in maps that don’t totally characterize an space’s danger.
What FEMA flood maps miss
FEMA’s maps are important instruments for figuring out flood dangers, however they’ve vital gaps that restrict their effectiveness.
One main limitation is that they don’t contemplate flooding pushed by intense bursts of rain. The maps primarily concentrate on river channels and coastal flooding, largely excluding the danger of flash flooding, notably alongside smaller waterways resembling streams, creeks and tributaries.
This limitation has turn out to be extra vital in recent times on account of local weather change. Rising world temperatures may end up in extra frequent excessive downpours, leaving extra areas susceptible to flooding, but unmapped by FEMA.
A map of a bit of Kerr County, Texas, the place a lethal flood struck on July 4, 2025, compares the FEMA flood map’s 100-year flood zone (purple) to First Road’s extra detailed 100-year flood zone (blue). The extra detailed map consists of flash flood dangers alongside smaller creeks and streams.
Jeremy Porter
For instance, when flooding from Hurricane Helene hit unmapped areas round Asheville, North Carolina, in 2024, it brought about an enormous quantity of uninsured injury to properties.
Even in areas which are mapped, just like the Camp Mystic web site in Kerr County, Texas, that was hit by a lethal flash flood on July 4, 2025, the maps could underestimate their danger due to a reliance on historic information and outdated danger assessments.
Political affect can gasoline lengthy delays
Moreover, FEMA’s mapping course of is commonly formed by political pressures.
Native governments and builders typically battle to keep away from high-risk designations to keep away from insurance coverage mandates or restrictions on improvement, resulting in maps that will understate precise dangers and depart residents unaware of their true publicity.
An instance is New York Metropolis’s enchantment of a 2015 FEMA Flood Insurance coverage Price Maps replace. The delay in resolving town’s issues has left it with maps which are roughly 20 years previous, and the present mapping challenge is tied up in authorized purple tape.
On common, it takes 5 to seven years to develop and implement a brand new FEMA Flood Insurance coverage Price Map. Because of this, many maps throughout the U.S. are considerably old-fashioned, typically failing to replicate present land use, city improvement or evolving flood dangers from excessive climate.
This delay instantly impacts constructing codes and infrastructure planning, as native governments depend on these maps to information building requirements, improvement approvals and flood mitigation tasks. In the end, outdated maps can result in underestimating flood dangers and permitting susceptible constructions to be inbuilt areas that face rising flood threats.
How know-how advances might help
New advances in satellite tv for pc imaging, rainfall modeling and high-resolution lidar, which is analogous to radar however makes use of gentle, make it potential to create sooner, extra correct flood maps that seize dangers from excessive rainfall and flash flooding.
Nevertheless, totally integrating these instruments requires vital federal funding. Congress controls FEMA’s mapping price range and units the authorized framework for a way maps are created. For years, updating the flood maps has been an unpopular subject amongst many publicly elected officers, as a result of new flood designations can set off stricter constructing codes, larger insurance coverage prices and improvement restrictions.
A map of Houston, produced for a 2022 research by researchers at universities and First Road, exhibits flood danger altering over the subsequent 30 years as local weather change worsens. Blue areas are in the present day’s 100-year flood-risk zones. The purple areas replicate the identical zones in 2050.
Oliver Wing et al., 2022
Lately, the rise of local weather danger analytics fashions and personal flood danger information have allowed the true property, finance and insurance coverage industries to rely much less on FEMA’s maps. These new fashions incorporate forward-looking local weather information, together with projections of maximum rainfall, sea-level rise and altering storm patterns – components FEMA’s maps typically exclude.
Actual property portals like Zillow, Redfin, Realtor.com and Properties.com now present property-level flood danger scores that contemplate each historic flooding and future local weather projections. The fashions they use establish dangers for a lot of properties that FEMA maps don’t, highlighting hidden vulnerabilities in communities throughout america.
Analysis exhibits that the provision, and accessibility, of local weather information on these websites has began driving property-buying choices that more and more take local weather change under consideration.
Implications for the longer term
As homebuyers perceive extra a couple of property’s flood dangers, that will shift the desirability of some places over time. These shifts can have implications for property valuations, neighborhood tax-revenue assessments, inhabitants migration patterns and a slew of different concerns.
Nevertheless, whereas these could really feel like modifications being introduced on by new information, the danger was already there. What’s altering is individuals’s consciousness.
The federal authorities has an vital function to play in making certain that correct danger assessments can be found to communities and People in all places. As higher instruments and fashions evolve for assessing danger evolve, FEMA’s danger maps must evolve, too.
