Flood danger in Columbus: More homes at risk, data shows
Columbus has nearly triple the number of properties at risk of flooding than are currently reflected on federal flood-plain maps, according to a new modeling tool released Monday.
The nationwide tool paints a picture of the U.S. as a country woefully under-prepared for damaging floods, both now and in the future.
The federal government’s best efforts to predict where flooding will strike have underestimated the risk to nearly 6 million homes and commercial properties primarily located in the nation’s interior, leaving them unprepared for potential devastation, the analysis shows.
According to the model, there are 10,053 homes and other structures in Columbus that fall into the substantial-risk category, meaning they face a 1% annual risk of flooding. The current Federal Emergency Management Agency map places just 3,789 properties in the city at that risk level.
For Franklin County, the new model estimates double the number of properties at substantial risk compared with the FEMA map.
Statewide, the model shows nearly half a million Ohio properties at risk, more than double the number recorded by FEMA. Across the seven-county central Ohio region, more than 19,000 properties now viewed as “at risk” are not reflected on the FEMA map.
The analysis was conducted by the First Street Foundation, a nonprofit organization in Brooklyn, New York, that paired dozens of scientists and engineers with university researchers. The team combined several existing models of sea-level rise, river flooding and simulations of extreme weather events into a single, nationwide flood assessment model that examined risk in all states except Alaska and Hawaii.
While insurance and investment companies, such as Blackrock, have long used their own private models to make decisions, First Street reported its findings in a report released Monday. The organization’s Flood Factor site enables users to view flood risks to individual properties, and it created a Flood Lab that allows additional academic researchers to further access data for research.
The modeling performed by the group is “exactly what we need to be doing,” said Kerry Emmanuel, a professor of atmospheric science at MIT who serves on First Street’s advisory board.
“Until recently, we didn’t have people putting all these little pieces together,” he said. “We had really good people working on that little piece of the problem and good people working on another little corner.”
First Street’s model found about 14.6 million homes and other structures across the country currently face a 1% annual risk of flooding, representing about one out of every 10 real-estate parcels nationwide. But First Street calculated that current maps developed by FEMA place just 8.7 million properties in the flood plain, a 40% undercount compared with what First Street found.
And it’s getting worse. In addition to a present-day analysis, First Street’s modeling incorporated 2050 projections from the International Panel on Climate Change, the United Nations’ primary scientific body on the issue. The conclusion: another 1.6 million properties will be at 1% annual risk of flooding by 2050.
The projections show an additional 2,000 properties in Franklin County will be in that risk category by 2050, including 1,527 in Columbus. During that time, flood risk would increase for an additional 26,671 properties in Ohio over First Street’s 2020 prediction.
The 1% threshold is the gold standard the federal government uses to assess which homeowners are required to purchase flood insurance. But experts say it’s also misleading, as it actually equates to a 1-in-4 chance of flooding over the course of a 30-year mortgage.
It’s important that the FEMA map reflects an accurate risk assessment because local and county planners use it to determine which areas are safe to develop.
“We rely heavily on the FEMA flood plain map partly because that is tied to the national flood insurance program as well as mitigation dollars,” said Franklin County Emergency Management Director Jeff Young.
The Mid-Ohio Regional Planning Commission uses the FEMA map when it makes long-term plans for things like new roads.
“We’re looking out 30 years at what growth patterns, what employment and development we think will look like, and then what the necessary transportation improvements would be to support that,” said Aaron Schill, director of data and mapping for MORPC.
Flooding is one issue they consider to understand how development and population will be distributed in the future.
“A change to that floodplain mapping, if it were adopted as an authoritative dataset ... that would really substantially impact how we model development in the future,” Schill said.
For emergency managers, the FEMA map is just one tool in the toolbox, Young said. They also rely heavily on first-hand experience and the expertise of local leaders.
“The flood-plain map doesn’t mean necessarily that if you’re on one side of an imaginary line you’re likely to flood and if you’re a foot over the other side of the line you’re safe from flooding,” Young said. “It’s always a matter of degrees.”
Both agencies said they’d welcome more data from a new product like First Street’s tool, but they still will exercise caution.
“We’re reluctant to take on newer, emerging things until they have been well tested and we know there is some rigor behind them,” Schill said.
Discrepancy not surprising
Many flood experts said the discrepancy between the two models isn’t surprising, given the limitations baked into FEMA’s calculations. The federal agency is stretched thin, struggling to keep its flood maps up to date, particularly for inland areas perceived to be less vulnerable than the coasts, experts said.
The agency also only looks back at historical data to assess where flooding could strike next, leaving out current and future models that assess where else risk might exist or even be growing.
Historic data is becoming less reliable with emerging weather patterns brought on by the climate crisis, according to Aaron Wilson, a research scientist at Ohio State University’s Byrd Polar and Climate Research Center. But models for predicting precipitation are also less reliable than scientists would like, Wilson said.
“We do anticipate the models are showing us more intense rainfall events,” he said. “By 2050, we’re looking at an average of three to five inches of rain more per year across the state of Ohio.”
FEMA’s maps and First Street’s model depict different kinds of risk and serve different purposes, said FEMA press secretary Lizzie Litzow.
The agency sees First Street’s Flood Factor as a tool to inform a property owner’s decision to buy flood insurance or take steps to reduce individual flood risk, said Litzow.