Lethal and damaging flash flooding in Texas and a number of other different states in July 2025 is 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 identical area of Texas Hill Nation the place a flash flood on July 4 killed greater than 130 individuals was hit once more with downpours per week later, forcing searchers to briefly pause their efforts to search out lacking victims. Different states, together with New Mexico, Oklahoma, Vermont, and Iowa, additionally noticed flash flood harm in July.
The U.S. Federal Emergency Administration Company’s flood maps are meant to be the nation’s major software for figuring out flood dangers. Initially developed within the Nineteen Seventies to assist the Nationwide Flood Insurance coverage Program, these maps, often called Flood Insurance coverage Fee 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 principle, the maps allow householders, companies, and native officers to grasp their flood danger and take applicable steps to arrange and mitigate potential losses.
A federal flood map of Kerrville, Texas, with the Guadalupe River winding by means of the center in purple, exhibits areas thought of to have a 1% annual probability of flooding in blue and a 0.2% annual probability of flooding in tan. Throughout a flash flood on July 4, 2025, the river rose greater than 30 toes at Kerrville. [Image: FEMA]
However whereas FEMA has improved the accuracy and accessibility of the maps over time with higher knowledge, digital instruments, and group enter, the maps nonetheless don’t seize every part—together with the altering local weather. There are areas of the nation that flood, some commonly, that don’t present up on the maps as in danger.
I examine flood-risk mapping as a university-based researcher and at First Road, a company 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 had 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 knowledge, and political affect over the updating of maps can result in maps that don’t absolutely symbolize 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 take into account flooding pushed by intense bursts of rain. The maps primarily deal with river channels and coastal flooding, largely excluding the chance of flash flooding, notably alongside smaller waterways equivalent to streams, creeks, and tributaries.
This limitation has grow to be extra necessary lately on account of local weather change. Rising international temperatures can lead to extra frequent excessive downpours, leaving extra areas susceptible to flooding, but unmapped by FEMA.
A map of a piece 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 contains flash flood dangers alongside smaller creeks and streams. [Image: Jeremy Porter]
For instance, when flooding from Hurricane Helene hit unmapped areas round Asheville, North Carolina, in 2024, it triggered an enormous quantity of uninsured harm to properties.
Even in areas which can be 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 knowledge and outdated danger assessments.
Political affect can gas lengthy delays
Moreover, FEMA’s mapping course of is commonly formed by political pressures.
Native governments and builders generally combat high-risk designations to keep away from insurance coverage mandates or restrictions on growth, resulting in maps which will understate precise dangers and depart residents unaware of their true publicity.
An instance is New York Metropolis’s attraction of a 2015 FEMA Flood Insurance coverage Fee Maps replace. The delay in resolving town’s issues has left it with maps which can be 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 Fee Map. Consequently, many maps throughout the U.S. are considerably old-fashioned, usually failing to mirror present land use, city growth, or evolving flood dangers from excessive climate.
This delay immediately impacts constructing codes and infrastructure planning, as native governments depend on these maps to information development requirements, growth approvals, and flood mitigation initiatives. In the end, outdated maps can result in underestimating flood dangers and permitting susceptible buildings to be in-built areas that face rising flood threats.
How know-how advances may help
New advances in satellite tv for pc imaging, rainfall modeling, and high-resolution lidar, which has similarities to radar however makes use of mild, make it potential to create quicker, extra correct flood maps that seize dangers from excessive rainfall and flash flooding.
Nevertheless, absolutely integrating these instruments requires vital federal funding. Congress controls FEMA’s mapping finances 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, greater insurance coverage prices, and growth restrictions.
A map of Houston, produced for a 2022 examine by researchers at universities and First Road, exhibits flood danger shifting over the subsequent 30 years as local weather change worsens. Blue areas are immediately’s 100-year flood-risk zones. The purple areas mirror the identical zones in 2050. [Image: Oliver Wing et al., 2022]
In recent times, the rise of local weather danger analytics fashions and personal flood danger knowledge 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 knowledge, 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 Houses.com now present property-level flood danger scores that take into account each historic flooding and future local weather projections. The fashions they use determine dangers for a lot of properties that FEMA maps don’t, highlighting hidden vulnerabilities in communities throughout the U.S.
Analysis exhibits that the provision, and accessibility, of local weather knowledge 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 few property’s flood dangers, which will shift the desirability of some places over time. These shifts may have implications for property valuations, group tax-revenue assessments, inhabitants migration patterns, and a slew of different issues.
Nevertheless, whereas these could really feel like modifications being introduced on by new knowledge, the chance was already there. What’s altering is individuals’s consciousness.
The federal authorities has an necessary position to play in making certain that correct danger assessments can be found to people and communities in every single place. As higher instruments and fashions evolve for assessing danger evolve, FEMA’s danger maps have to evolve, too.
This text, initially printed July 12, 2025, has been up to date with one other spherical of flooding in Texas on July 13.
Jeremy Porter is a professor of quantitative strategies within the social sciences on the Metropolis College of New York.
This text is republished from The Dialog underneath a Artistic Commons license. Learn the unique article.
