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As climate changes, floodplain maps a potential 'weak link'

Floodplain maps, which help determine whether people need to buy flood insurance or not, may not be presenting the fullest picture because of climate change.
In Coatesville, Pennsylvania, heavy rains from the remnants of Hurricane Ida in September led to flooding in areas that were not located in a floodplain. Homes were left with extensive water damage on some streets.
Coatesville, Pennsylvania is 40 miles west of Philadelphia and more than 1,000 miles from where Hurricane Ida made landfall, but streets there suddenly became rivers and flooded basements, when the storm’s remnants dropped heavy rains.
With climate change and a warming planet, the atmosphere is able to hold more moisture - a dump heavier rains - which could potentially lead to more inland flooding in places where it has not happened before.
Posted at 9:01 AM, Oct 06, 2021
and last updated 2021-10-06 12:27:26-04

COATESVILLE, Pa. — For Alicia Milbourne, a new urgency and anxiety are sweeping through her neighborhood.

“They’re scared,” she said. “There are sandbags. We got sandbags and everything ready.”

The sandbags are a new addition to her home. Heavy rains from the remnants of Hurricane Ida carved a path from Louisiana, all the way up to the Northeast, including the town of Coatesville, Pennsylvania.

“It was evident that something was going on with the way that the rain was coming down,” said Rob Marshall, Associate Pastor at New Life in Christ Fellowship Church. “It was a pretty intense storm, to say the least.”

Coatesville is 40 miles west of Philadelphia and more than 1,000 miles from where Hurricane Ida made landfall, but streets there suddenly became rivers when the storm’s remnants dropped heavy rains.

“The water was rising too, too, too fast,” Milbourne said. “So, as they’re across the street trying to get a family of five out, I'm trying to make a decision whether I'm going to drown to hold a 10-year-old up.”

Residents shared photos with us of the water damage, including at New Life in Christ Fellowship Church.

“Oh my, it was terrible,” said church administrator LaTadra Mosley. “It was terrible.”

Most people do not have flood insurance there because the area is not located in a traditional floodplain. The flooding took everyone by surprise, but experts say that’s something that can no longer be afforded.

“There are a lot of people who may be underestimating their risk,” said Radley Horton, a research professor at the Lamont-Doherty Earth Observatory at Columbia University’s The Earth Institute. “With climate change, there's more heat in the atmosphere and a warmer atmosphere can hold more moisture.”

That could potentially lead to heavier rain events and more inland flooding, like what happened with the remnants of Hurricane Ida. Horton said floodplain maps, which help determine whether people need to buy flood insurance or not, may not be presenting the fullest picture.

“Floodplain maps are a real weak link in our plan,” he said. “We have heavier rain events happening, so those old maps, which might not have even been totally accurate in the past, become even more inaccurate, even more in need of updating, as we see these heavier rainfall events today and out in the future.”

Back in Coatesville, the recovery is continuing.

“The volunteers that came out to this are the heroes in this story,” Associate Pastor Marshall said.

Church members are now canvassing the area by going door-to-door to see what help residents still need, while also preparing to open a center to address their long-term needs.

“Yes, we can repaint your home, we can repair your home, but we want to make sure that you're OK inside. We want to make sure you're OK up here,” said Mosley, referring to counseling services they are preparing to offer.

Yet, the concerns about the future linger.

“Climate change is real,” Marshall said. “And if there's not some changes made to the infrastructure of the city, it will happen again.”

That is exactly what worries residents.

“It's a problem that's not going to be fixed overnight,” Milbourne said, “and we just got to better prepare, I guess.”