Number of properties at substantial flood risk
in 2020, by county
5,000
50,000
200,000
Number of properties at substantial flood risk in 2020
by county
5,000
50,000
200,000
Number of properties at substantial flood risk in 2020
by county
200,000
5,000
50,000
WASH.
MAINE
MONT.
N.D.
VT.
MINN.
ORE.
N.H.
N.Y.
IDAHO
WIS.
MASS.
S.D.
MICH.
WYO.
R.I.
CT.
IOWA
PA.
NEB.
N.J.
OHIO
IND.
NEV.
ILL.
DEL.
MD.
UTAH
W. VA.
COLO.
VA.
MO.
KAN.
CALIF.
KY.
N.C.
OKLA.
TENN.
ARK.
ARIZ.
S.C.
N.M.
MISS.
ALA.
GA.
LA.
TEXAS
FLA.
Number of properties at substantial flood risk in 2020
by county
5,000
50,000
200,000
WASH.
MAINE
N.D.
MONT.
MINN.
VT.
N.H.
ORE.
WIS.
N.Y.
IDAHO
MASS.
MICH.
S.D.
WYO.
R.I.
CT.
IOWA
PA.
N.J.
NEB.
NEV.
OHIO
IND.
ILL.
DEL.
UTAH
W. VA.
MD.
VA.
COLO.
MO.
KAN.
CALIF.
KY.
N.C.
OKLA.
TENN.
ARK.
ARIZ.
S.C.
N.M.
ALA.
GA.
MISS.
LA.
TEXAS
FLA.
When Hurricane Harvey struck Southeast Texas in 2017, it provided a real-life stress test of the plans for flood risk in a highly vulnerable region. Southeast Texas failed that test. More than half of the homes engulfed by floodwaters were located outside city- and federally designated 100-year floodplains.
That storm led to a whole-scale rethinking of zoning regulations in the Houston area, and it highlighted the gaping flaws in the country’s system of analyzing and communicating flood risks to property owners and prospective buyers.
Now, an exhaustive report out Monday shows that nationally, there are at least 6 million households that are unaware they’re living in homes that have a 1 percent chance of flooding in each year — putting them within a “100-year” flood zone. This is nearly 70 percent more homes at substantial risk of flooding than are within the Federal Emergency Management Agency’s Special Flood Hazard Areas, a designation that determines eligibility for the National Flood Insurance Program.
[In these two neighborhoods, flooding from Harvey went beyond the worst projections]
This count is set to grow substantially in coming decades due to the effects of climate change, including sea level rise, which will make hurricane storm surges more damaging, as well as precipitation extremes.
2020-2050 change in proportion
of properties at substantial risk
-30%
-0
+30%
+260%
2020-2050 change in proportion of properties
at substantial risk
-30%
-0
+30%
+260%
2020-2050 change in proportion of properties at substantial risk
-30%
-0
+30%
+260%
WASH.
MAINE
MONT.
N.D.
VT.
MINN.
ORE.
N.H.
IDAHO
WIS.
MASS.
S.D.
N.Y.
MICH.
WYO.
R.I.
CT.
PA.
IOWA
NEB.
N.J.
OHIO
NEV.
IND.
ILL.
DEL.
MD.
UTAH
W. VA.
COLO.
VA.
KAN.
MO.
KY.
CALIF.
N.C.
TENN.
ARIZ.
OKLA.
S.C.
N.M.
ARK.
GA.
ALA.
MISS.
LA.
TEXAS
FLA.
2020-2050 change in proportion of properties at substantial risk
-30%
-0
+30%
+260%
WASH.
MAINE
MONT.
N.D.
MINN.
VT.
ORE.
N.H.
IDAHO
MASS.
WIS.
S.D.
N.Y.
MICH.
WYO.
R.I.
CT.
PA.
IOWA
N.J.
NEB.
NEV.
OHIO
IND.
ILL.
DEL.
UTAH
MD.
W. VA.
COLO.
VA.
KAN.
MO.
KY.
CALIF.
N.C.
TENN.
ARIZ.
OKLA.
S.C.
ARK.
N.M.
GA.
ALA.
MISS.
LA.
TEXAS
FLA.
A warming climate is poised to wreak havoc on the housing market, particularly if risk is not properly priced. Homeowners could be stuck owning properties that are literally and financially underwater, and insurers and lenders could face a financial reckoning of their own.
The report, from the nonprofit flood research and communications group First Street Foundation, is aimed at leveling the playing field between buyers and sellers, and democratizing specialized flood risk analyses that insurance companies and consulting firms are producing but charge hefty sums to access.
Now, a prospective buyer can see a property’s flood risk score, which First Street calls the “Flood Factor,” along with a map showing flood information, for 142 million properties in the Lower 48 states.
First Street is providing property-level mapping free on its website. Using peer-reviewed models and an approach that looks at both the changing risks of flooding and probable depths of each flood, the First Street analysis assigns each property a “Flood Factor,” which is a score on a 10-point scale, to allow prospective buyers to better understand the flood probabilities associated with a particular property.
First Street’s cumulative flood-risk model was developed using contributions from Fathom Global, Rhodium Group, the University of Bristol, Columbia University, George Mason University and MIT, as well as government agencies including FEMA, the U.S. Geological Survey and the National Oceanic and Atmospheric Administration (NOAA). For example, to determine changes to storm surge flooding over time, the model incorporates an MIT analysis of 50,000 synthetic hurricanes. And to find the historical flood risk for a specific property, the First Street re-created the extent of flooding from 50 historical river and storm surge events to find homes that flooded from a specific storm.
Not knowing flood risks can lead to disaster
Rescue boats fill a flooded street as flood victims are evacuated as floodwaters from Tropical Storm Harvey rise in Houston in August 2017. (David J. Phillip/AP)
Having more insight into potential future flood risks might have made a critical difference to Marni Axelrad and her husband, who bought a home in Houston’s Meyerland neighborhood in late 2014. “It would have been useful to have that information,” Axelrad said. “At least we wouldn’t have been caught as much by surprise as we were.”
They made certain that the house they bought, while it did require flood insurance, had never flooded in the past. But they had no idea how vulnerable it was to flooding in the future — the very near future, as it turns out.
The following spring, a massive rain event led to half a foot of water in the house. The couple and their three children had to move out for five months while their home was gutted. Another flood the following year claimed one of their cars as water crept to the front door.
[A year after Harvey, this Houston neighborhood was still recovering]
“Every time it rained, we’d pick up all our stuff from the floor,” Axelrad said.
Then came Hurricane Harvey and its unprecedented rains. The storm left 2½ feet of water inside. Everything was lost. This time, the family was displaced for eight months. In addition to gutting the house again, they spent hundreds of thousands of dollars to raise the home roughly 6 feet higher than where it stood when they bought it.
“We had to take out another loan,” said Axelrad, adding it wasn’t feasible to just walk away from the property and virtually impossible to sell it. She said it had never occurred to the couple that the home was at more risk than the one they had moved from, barely a mile away.
Having reliable data that could have told them that, or at least given a warning about what might lie ahead, could have helped.
“Had we known that,” she said, “we would have made a different decision to begin with.”
First Street’s modeling shows flood risk is already higher than thought, and it’s getting worse
Water from Addicks Reservoir flows into neighborhoods from floodwaters brought on by Tropical Storm Harvey in Houston on Aug. 29, 2017. (David J. Phillip/AP)
First Street’s work shows just how dramatically Americans’ exposure to flood hazards is expected to increase during the next 30 years, which is the term of a typical mortgage.
Whereas the model finds about 14.6 million properties have a substantial level of risk now, that grows to 16.2 million by 2050, but there are considerable uncertainties involving changing precipitation patterns that could inflate that number further.
The new First Street model is based on peer-reviewed methods, but the new analysis is pending publication in a scientific journal.
[Sea level rise is eroding home value, and owners might not even know it]
The model determines the current and future probability of types of flooding, including tidal, storm surge, and flooding from heavy rainfall, as well as river-related flooding. It uses a return period probabilistic approach, meaning that it looks at flood events ranging from 1-in-2-year events to 1-in-500-year events from 2020 through 2050, while mapping the inundation depths associated with each.
Doing it this way, First Street was able to estimate the cumulative flood likelihoods for any depth of water at any location in the United States. (The organization defines the “substantial risk” metric as an inundation of 1 centimeter or more to a property during the 100-year return period.)
Coastal and inland states face growing risks
Damage to Highway 23, southwest of Duluth, Minn., on June 17, 2018. (Carlton County Sheriff's Office/AP)
The state-by-state analysis contained in the report provides insights into where flood risk is especially underestimated today, as well as where it may escalate dramatically in coming years.
By 2050, First Street’s model found the number of properties at substantial risk of flooding will increase the most in Louisiana, Delaware, New Jersey, Florida and South Carolina. Each is a coastal state facing increased risks of storm surge-related flooding and sea level rise. However, inland states will see flood risks increase, too, including a 5.4 percent jump in the proportion of properties at substantial risk in Ohio, 3.2 percent increase in Kentucky and Tennessee, and a 7.7 percent increase in Idaho.
Cities with the greatest proportion of properties at substantial risk of flooding. (First Street Foundation)
Also, because First Street’s models take into account flooding from heavy rainfall events, places that show few areas within FEMA’s 100-year flood zones, such as Chicago, show up high atop their list of places with underappreciated risk in the present day. A total of 13 percent of properties in the city are at substantial risk of flooding, mainly due to flash flooding from heavy rains, according to First Street’s model. This compares to less than 1 percent of properties at the same level of risk as calculated using FEMA’s flood maps for the city.
“More information and transparency for consumers and home buyers and renters about flood risk is critical, no matter where it comes from,” said Laura Lightbody, project director for the flood-prepared communities initiative at the Pew Charitable Trusts. “We know that residents and home buyers don’t have this type of information, or it’s very limited.”
[Flooded again: Climate change is making flooding more frequent in Southeast Texas]
Currently, she said, the nation has a patchwork of disclosure laws in different states that often don’t take into account future flood risks. FEMA’s flood maps are often outdated and incomplete, she said, and many states don’t require property owners to disclose the flood history information to prospective buyers. “This is not a consumer-friendly world we are talking about,” she said.
The real estate industry, for example, hasn’t always welcomed increased flood disclosures, due to concerns that they could slow sales or cut property prices.
“Right now, if you, the average person, [are] buying a home, it’s really hard to actually understand your flood risk,” said Melissa Roberts, founder and director of the American Flood Coalition, a nonpartisan group of local, military and business leaders aimed at helping communities adapt in the face of rising seas and more frequent flooding.
She said it’s imperative for home buyers, homeowners and renters to have better information about the risks before a disaster arrives.
“Better to find out through data than to get flooded and lose their life savings,” said Roberts, who previously worked at First Street as director of strategy.
Maps and flood scores are not a panacea
An image of the FloodFactor score and breakdown of cumulative risk for city hall in Charleston, S.C. (First Street Foundation)
Roberts hopes the availability of more information like that from First Street will create pressure on governments and communities to put in place more proactive policies to mitigate flood risks, rather than merely spending money after a crippling flood to rebuild. “There just hasn’t been political will to grapple with any of these issues because they are difficult and they are getting worse,” she said.
She called Monday’s data release “incredibly important, but it’s only the first step” that needs to be followed by action. “These are big questions that need to be taken up at the city, state and federal level. The best thing this data can do is create understanding and a call to action that then leads to better policy.”
Putting more information into people’s hands won’t necessarily lead to better decisions, either.
“People generally do a lousy job of acting on information, particularly statistical information,” said Rob Moore, a senior policy analyst who studies flooding at the Natural Resources Defense Council. He said there’s a difference between buying a home that has a 1 percent chance of flooding each year vs. knowing a home has flooded three times in the past five years.
Nicholas Pinter, a professor and director of the University of California at Davis Center for Watershed Sciences, says in addition to the well-known bureaucratic delays that come with updating FEMA’s flood maps, they only tell people whether they’re in or out of a flood zone, rather than showing the risk gradients.
“I think First Street Foundation is a big step in the right direction, it’s not all the way there,” he said.
Read more
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The signal of human-caused climate change has emerged in everyday weather, study finds
