Harris County's 100-Year Floodplain Could Grow 43% Under New FEMA Maps

Expansions driven by higher rainfall, more development, and better modeling technology

Published on Feb. 12, 2026

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According to a Chronicle analysis, Harris County's 100-year floodplain could grow by more than 40% under draft maps newly released by the Federal Emergency Management Agency (FEMA). The agency is gathering feedback from local officials before beginning a broader public review process. If adopted, the new maps would mark the first comprehensive update to Harris County's floodplain boundaries since 2007.

Why it matters

The changes reflect new data showing rainfall rates are over 30% higher than previous models assumed, as well as the impact of decades of development that has replaced natural soil that once absorbed water. The expansions could have significant financial implications for homeowners who may be newly required to purchase flood insurance.

The details

The 100-year floodplain would grow by about 130 square miles, a 43% increase, while the 500-year floodplain would increase by about 62 square miles, or 30%. Floodways, the most dangerous areas, would shrink by about 5%. The reductions in some neighborhoods reflect the impact of large-scale flood mitigation projects the county has undertaken in recent years.

  • FEMA posted the draft maps last week and is now gathering feedback from local officials.
  • The agency will then have 60 days to prepare for a broader public release, at which point residents will be able to formally submit comments and challenge the floodplain designations of their properties.
  • During Thursday's commissioners court meeting, officials urged the Harris County Flood Control District to be more transparent and release additional information to the public.

The players

FEMA

The Federal Emergency Management Agency, which is responsible for updating the floodplain maps.

Harris County Flood Control District

FEMA's local partner in the floodplain map update process.

Sam Brody

An environmental science professor at Texas A&M University whose research found that sprawling growth has consistently worsened flood damage.

Milton Rahman

The Harris County engineer, who said the county will have the best flood data in the region and should ask FEMA for more flood insurance discounts for its residents.

Larry Dunbar

A water resources engineer and consultant for Fort Bend County, who said he expects significant pushback from homeowners and developers over the new floodplain maps.

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What they’re saying

“We're developing and not thinking about downstream impacts. I think that's the biggest driver of the expanding floodplains.”

— Sam Brody, environmental science professor, Texas A&M University (Houston Chronicle)

“People who didn't have to have flood insurance before are all suddenly going to be hit with potentially thousands of dollars.”

— Sam Brody, environmental science professor, Texas A&M University (Houston Chronicle)

“If you have that much more rain, you would expect the floodplains to go up everywhere, including the floodway. That's not rocket science.”

— Larry Dunbar, water resources engineer and consultant, Fort Bend County (Houston Chronicle)

What’s next

The version of the maps currently posted on FEMA's website is meant for floodplain administrators and local elected officials, who will have 30 days to review the draft. FEMA will then have 60 days to prepare for a broader public release, at which point residents will be able to formally submit comments and challenge the floodplain designations of their properties.

The takeaway

The expansions of Harris County's floodplains highlight the growing threat of flooding driven by climate change, development, and outdated modeling. This could lead to significant financial burdens for homeowners who may be newly required to purchase flood insurance, underscoring the need for more proactive flood mitigation efforts and policies that account for the region's changing flood risks.