New study finds 'alarming' high flood risk for 17 million Americans on Atlantic and Gulf coasts

WASHINGTON (AP) — More than 17 cardinal radical on the U.S. Atlantic and Gulf coasts are astatine the highest hazard of being affected by flooding, with New York and New Orleans lasting out, according to 1 of the astir broad studies ever of flood risk.

Researchers astatine the University of Alabama utilized 16 antithetic factors including the geographic hazards, the colonisation and infrastructure exposed and the vulnerability of radical surviving there. They past brought successful past damages from the Federal Emergency Management Agency's database and applied 3 antithetic artificial quality tools to fig retired flood risks from Texas to Maine, calculating that 17.5 cardinal radical were astatine “very high” hazard and an further 17 cardinal were astatine “high" risk, the adjacent level.

The authors looked astatine each sizes of flooding and examined separately what FEMA considers the astir extreme, which are the apical 1% of events. The survey recovered 4.3 cardinal radical on the coasts to beryllium astatine the highest level of hazard of utmost flooding, but 20.5 cardinal to beryllium astatine precocious risk, the 2nd highest level.

They recovered a batch of vulnerability, highlighting 8 antithetic cities from Houston, which flooded successful 2017’s Hurricane Harvey, to New York, which was inundated successful 2012’s Superstorm Sandy.

Wednesday's survey successful the diary Science Advances recovered that New York City has 4.75 cardinal radical astatine the 2 highest hazard levels for each flooding, with much than 200,000 buildings apt to beryllium damaged.

And portion the fig of radical astatine hazard successful New Orleans is acold lower, astir 380,000, it involves 99% of the city's population. That doesn't mean 99% of the radical volition beryllium affected successful the adjacent hurricane oregon nontropical flood, but that they mightiness beryllium depending connected the storm's idiosyncratic way and rainfall pattern, said survey co-author Wanyun Shao, a clime idiosyncratic astatine the University of Alabama.

“Just look astatine the magnitude,” Shao said. “Those numbers are shocking, are alarming.”

The aged and mediocre are astir astatine risk

“When the adjacent large tempest hits New York City, erstwhile the adjacent Hurricane Katrina -like hurricane makes landfall successful New Orleans, radical volition get hurt, particularly those socially susceptible populations,” Shao said referring to the poor, the elderly, children and the uneducated.

Shao and extracurricular experts said the numbers stunned them adjacent though they were acquainted with the worsening effects of clime change.

“New York is known to beryllium susceptible to floods and it has the largest population. But the information that New York has astir an bid of magnitude much flood-exposed colonisation than immoderate different metropolis is surprising,” said Alex de Sherbinin, a geographer who directs Columbia University’s Center for Integrated Earth System Information. He wasn’t portion of the study.

Flood problems are becoming much predominant successful New York and New Orleans due to the fact that of human-caused clime change, the survey said.

Other cities are besides threatened

Jacksonville has 679,000 radical astatine precocious oregon precise precocious hazard of flooding, portion Houston is conscionable down astatine conscionable nether 600,000. Other cities highlighted see Miami, Norfolk, Virginia, Charleston, South Carolina, Mobile, Alabama.

Shao and extracurricular experts said what separates her survey from others is the sheer comprehensiveness of each the factors it considers, including sinking onshore and pavement that doesn't let h2o to seep into the ground, arsenic good arsenic incorporating quality societal vulnerability specified arsenic poorness and age.

“This could beryllium applied to different places successful the world, specified arsenic Manila,” said University of Virginia engineering prof Venkataraman Lakshmi, who heads the hydrology conception of the American Geophysical Union, referring to the superior of the Philippines. He wasn't portion of the study, but said the flooding problems it highlights volition get much predominant and aggravated owed to human-caused clime change.

Columbia University's Marco Tedesco, who wasn't portion of the study, said "it reinforces the important conception that aboriginal flood disasters are not conscionable astir water—they are astir wherever radical live, however cities are built, and who is slightest protected.”

Actions tin lessen the risk

De Sherbinin said, "the investigation of the flood hazard factors is important for section planners, exigency managers, and adjacent road crews and inferior providers. We each cognize that debased lying areas are much flood prone, but the information they person assembled supply much insights into flood risk, peculiarly for flash floods.”

Study pb writer Hemal Dey, a geospatial scientist, said helium hopes section officials look astatine not conscionable gathering much dams and levees, but much earthy infrastructure specified arsenic wetlands, grasslands, rainfall gardens and estuaries.

“The probe is coagulated confirmation of what exigency managers person been saying for years. Realtors volition hatred it,'' said Craig Fugate, a erstwhile FEMA manager who wasn't portion of the study. "The harder question is what we’re really going to bash astir it."

___

The Associated Press’ clime and biology sum receives fiscal enactment from aggregate backstage foundations. AP is solely liable for each content. Find AP’s standards for moving with philanthropies, a database of supporters and funded sum areas astatine AP.org.

Copyright 2026 The Associated Press. All rights reserved. This worldly whitethorn not beryllium published, broadcast, rewritten oregon redistributed without permission.