Above, new flood maps adjusted for climate enhanced rain events show big increases in incidence of 100 year floods. New York City and the northeast are particularly vulnerable, and expensive to fix. But there are solutions being tried.
The PBS video points out how long forgotten water features, buried under concrete and development, still make themselves felt during extreme rain events.
Below, Detroit’s “Ghost Streams” – hidden footprint of historic waterways, predict flooding risk, and hit primarily low income people of color.
Setting out by foot or by bike, Joanne Coutts has mapped more than 200 miles of buried creeks and wetlands across Detroit’s landscape over the last year-and-a-half.
Her work is part of a growing interest in buried and forgotten historical waterways to better inform water and flood management in the present. When heavy rain pours, buried ghost streams flow, contributing to flooding in Detroit’s most vulnerable neighborhoods and causing significant damage, University of Michigan-Dearborn researchers found.
Since 1905, 85% of the city’s historic streams have been buried for urban development, leading to long-term ramifications for Detroit’s most vulnerable residents.
These streams and wetlands are a little-examined flood risk, according to a new study published in City and Environment Interactions. Using historical maps to identify once-active waterways, researchers compared the streams to flood risk data and historic Home Owners’ Loan Corporation redlining maps, finding that flooding disproportionately impacts redlined neighborhoods.
“Sometimes people are subjected to flood risk and they don’t even know why, and it could have something to do with history,” said Jacob Napieralski, lead author of the study and a geology and geographic information systems professor at the University of Michigan-Dearborn.
“The landscape doesn’t really forget, it has a memory, and when it’s time, water will occupy those spots,” Napieralski said.
In the 1930s, the federal government drew red lines around neighborhoods it felt were too risky for mortgage loans – the basis was often whether people of color lived there – and the neighborhoods were given rankings from “A” to “D,” with “D” being the most risky.
Napieralski’s research team found that in metro Detroit, 96% of extreme flood risk is concentrated in neighborhoods that were rated “C” and “D,” while just 3.9% are in “A” and “B” neighborhoods.
A number of confounding factors associated with redlining increase flood risk and drive health concerns.
Redlined neighborhoods are more likely to host industry that, when it rains, can cause contaminants to be mixed in with floodwater. They found that more than a fourth of Detroit’s formerly redlined neighborhoods are now zoned for industry, compared to 0% of neighborhoods that received the grade “A.”
They also found that residents in redlined neighborhoods are less likely to have flood insurance and vegetation like rain gardens and trees, which can mitigate flooding.
Napieralski said it’s important that cities start mapping this hidden hydrology to fully inform residents about their flood risk and make decisions about flood mitigation investment. It adds to previous research which found that 43% of Detroiters have experienced flooding and that very old and very new homes were the most likely to be impacted.
This is why I bought flood insurance last year. I don’t live near water but when 8 inches of rain could fall on anyone in less than a day, it’s better to be safe than sorry.