Is your home prone to flooding? New maps show thousands more Greater Lansing properties at risk
Sarah Lehr
Maps from the Federal Emergency Management Agency significantly under-estimate the chances of flooding, according to scientists who found thousands more Greater Lansing properties to be at risk of flooding.
A team of more than 80 researchers with the nonprofit First Street Foundation recalculated flood risk nationwide to account for climate change and other factors.
Compared to FEMA's maps, First Street's map show an increase of nearly 60% in the total number of flood-prone properties in Ingham, Eaton and Clinton counties.
Those calculations matter to residents as they decide whether to buy flood insurance and where to build or buy homes and businesses. According to the new maps, millions of Americans face previously under-acknowledged flood risk, leaving them vulnerable to displacement and financial loss.
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First Street considered climate change
First Street partnered with universities to build on data from FEMA and peer-reviewed sources. The nonprofit added a predictive element to calculate the changing probability of flooding over time. Climate change is increasing that risk as it alters water levels and contributes to heavier rainfall and more extreme storms, researchers noted.
First Street also took at a more detailed look at the risks posed by small streams and tributaries, researchers said.
In Ingham County, FEMA considers 3,962 properties, or 3.9% of properties in the county, to be in a 100-year floodplain, meaning the properties have a 1% or greater chance of flooding in a given year.
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But First Street Foundation found nearly one-and-a-half times as many Ingham County properties to be at that risk level.
According to First Street, 5,816 Ingham County properties, 5.7% of all properties in the county, have at least a 1% chance of flooding annually.
The increase was just as pronounced in Clinton County, with First Street finding 2,091 flood-prone properties (5.7% of properties in the county) compared to FEMA's identification of 1,397 properties (3.8%).
Eaton County saw a two-fold increase, with First Street identifying 3,181 flood-prone properties (3.4%) compared to FEMA's 1,582 (6.9%).
FEMA: New maps complement federal research
"The FEMA Flood Insurance Risk Maps and First Street Foundation maps do not conflict with each other, rather they complement one another by depicting different types of risk and will be helpful in different ways for an individual to determine flood risk," a FEMA spokesperson said. "Users should explore the differences between the maps to build a more comprehensive understanding of flood risk."
Across the country, First Street estimated nearly 6 million flood-prone properties, including 400,000 in Michigan, are excluded from FEMA's calculations.
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"In environmental engineering, there is a concept called stationarity, which assumes that today is going to be like yesterday, and tomorrow is going to be like yesterday," said Ed Kearns, First Street's chief data officer. "This concept used to work, but with a changing environment it's a poor assumption and no longer does. FEMA's method assumes stationarity, First Street's does not."
First Street researchers did assume that structures like dams and levees are well-maintained and so did not take into account the risk of incidents like the failure of two dams this spring, which led to historic flooding in Midland County.
Model: Ingham, Clinton, Eaton county flood risk will increase over 30 years
First Street also looked at flood risk three decades into the future with the intention of reflecting the lifespan of a 30-year mortgage.
A warming atmosphere, fueled by increased carbon emissions from humans, creates more evaporation, making more water available in the atmosphere to form rain clouds. Sea levels are rising due to melting ice caps and changing circulation while warmer ocean temperatures create fodder for hurricanes and other storms.
By 2050, Ingham County will see a 3.3% increase in its number of flood-prone properties, as compared to a 2.3% increase for Eaton County and a 1.8% increase for Clinton County, First Street estimated.
The following GIF, courtesy of The Pudding, shows how Lansing's flood risk changes over time, based on calculations from the First Street Foundation.
Related: Property owners near Red Cedar River won't be charged for study to remap floodplain
FEMA is updating Lansing-area maps
FEMA's process for remapping floodplains is costly and vast swaths federal maps are out of date, Ronda Oberlin, Lansing's hazard mitigation coordinator, acknowledged.
Still, First Street's use of nationwide modeling likely makes its data less granular than FEMA's, she said. Oberlin advised homeowners to make decisions about flood risk based on multiple sources, including FEMA.
"FEMA is continuously working with our agency partners to develop a more comprehensive picture of flood hazard and flood risk across the nation," a spokesperson for the agency said in a statement. "We are leveraging the latest data and technologies, while being good stewards of taxpayer dollars and serving the diverse need of the public."
Within the city of Lansing, FEMA maps took effect in 2011, making them nearly a decade old, according the federal agency's website.
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The United States Geological Survey is redrawing those FEMA maps in the Lansing-area. Data from that process is set to be released in March 2021 and the maps should receive final approval in spring 2024, Oberlin said.
Oberlin expects those updated maps will actually shrink the span Lansing's calculated floodplain because infrastructure has improved since FEMA last drew the maps. At least 50 homes in Lansing could leave the floodplain, she said.
Rising flood insurance costs are a concern
Updated federal maps will not change actual risks of flooding, but a reduction in calculated risk will help residents struggling to afford flood insurance, city officials said.
People with federally backed mortgages are required to carry flood insurance if they own property within a 100-year floodplain as calculated by FEMA, and there are potential fines if a lender discovers a homeowner lacks the insurance.
Related: It's not just the Great Lakes. Flooding threatens inland Michigan, too
But flood insurance premiums are rising, making those costs untenable for many.
Half the homes within Lansing's floodplain are worth $50,000 or less and flood insurance costs are on pace to equal mortgage payments for 32% of homes within the flood zone, according to numbers released by Lansing's Office of Emergency Management in 2019.
Lansing officials say they encourage residents to buy flood insurance if they do not live in a federal flood zone, and premiums tend to be lower for homes and businesses outside of a FEMA floodplain.
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Actual flood risk remains a concern, particularly if hundreds of residents are uninsured or under-insured for a flood.
The city promotes flood mitigation, such as by encouraging people to fill basements in areas with high flood risk, Oberlin said. And Lansing has been using federal funding to buy up homes in low-income, flood-prone areas, such as the Baker-Donora and Urbandale neighborhoods.
Look up your flood risk
Check to see if your home is in a FEMA-desigated floodplain by visiting msc.fema.gov.
Visit floodfactor.com to look up a specific address using First Street's calculations, which assess risk on a scale of one to 10. First Street plans to continually update its model and to revise data annually.
Contact reporter Sarah Lehr at slehr@lsj.com. Follow her on Twitter @SarahGLehr.