A comprehensive new assessment of flood risk, released this week by the nonprofit First Street Foundation, exposes blind spots in FEMA’s maps to show just how vulnerable the nation’s properties are. Built by researchers from private companies and universities, the model calculates the cumulative risk for every property in the contiguous United States from rainfall, storm surge, tidal and river flooding. FEMA says 8.7 million properties are in areas susceptible to a “hundred-year flood” — a flooding event with a 1% chance of occurring in a given year. The new data says there are 14.6 million properties at risk. […]
In Cook County, where Chicago and its suburbs are located, the new model found more than 150,000 properties are at high risk — about six times as many as FEMA’s estimate. […]
Illinois has warmed about 1.2 degrees and experienced 10% to 15% more precipitation over the last century, according to the Illinois State Climatologist’s office. But the rainfall is not uniform — it’s increasingly coming down in bunches. In the Great Lakes region, the most powerful storms have increased 35% between 1951 and 2017.
Last year, state scientists updated the standard for new construction requiring state permits, including the design of storm sewers, retention ponds and road drainage, to accommodate increasing precipitation trends.
Because state and local officials use FEMA maps to help guide and justify their planning decisions, they tend to focus almost exclusively on the areas the agency has deemed high risk.
For example, the Metropolitan Water Reclamation District of Greater Chicago has spent around $22.2 million helping municipalities acquire 90 flood-prone properties, raze the structures on those properties and keep those areas as open space. The agency has designated additional high-risk zones beyond the FEMA maps, but so far, the properties purchased throughout Cook County have been located in FEMA’s high-risk zones. […]
In Illinois alone, there has been more than $2.3 billion in documented property damage from flooding in urban areas between 2007 and 2014, according to a study led by the Department of Natural Resources. Over 90% of those insurance and disaster assistance claims were for properties outside of the FEMA floodplain — where residents weren’t required to buy flood insurance and may not have been alerted to the risk when they bought their homes.
If anything, the First Street model still underestimates risk in some properties, because its analysis is based on ground-level flooding, as are the FEMA maps. Andrew Smith, chief operations officer at Fathom, said basements can flood more frequently than the model suggests. […]
Between 2007 and 2016, there were nearly 230,000 flood-related claims in Chicago resulting in $433 million in payouts, according to a 2018 report from the Center for Neighborhood Technology. Of those, 87% of paid flood claims were located in communities of color.