When Angela Chalk first heard there were ways that ordinary people could offset flooding in New Orleans, she was skeptical.

Her neighbors in the Seventh Ward knew all about heavy rains that brought knee-high floodwaters, spilling into porches and marooning cars and homes, and were frustrated that it was something they felt powerless to stop.

Then she heard Jeff Supak, head of a nonprofit organization now called Water Wise Gulf South, talk about how simple fixes like rain gardens and vegetated ditches, also known as bioswales, could soak up extra rain.

She challenged Mr. Supak to prove it.

50 States, 50 Fixes is a series about local solutions to environmental problems. More to come this year.

“I didn’t know if this was some lamebrain, cockamamie excuse post-Katrina, because so many people were telling us they could do so many things post-Katrina to help improve communities,” recalled Ms. Chalk, the executive director of a nonprofit group that focuses on public health and sustainability, referring to the 2005 hurricane that ravaged the city.