Following the success of The Storm of the Century (2015), a New York Times bestseller about the Great Gulf Hurricane of 1900, weather expert Al Roker, host of NBC’s Today, examines the country’s deadliest flood, Ruthless Tide: The Heroes and Villains of the Johns­town Flood, America’s Astonishing Gilded Age Disaster (Morrow).

“It was a big deal,” says Roker, noting that there have been songs about the Great Johnstown Flood, and even a couple of movies. “The more [I] looked into it and learned it was a matter of class, environmental issues, and a lot of things that hold true today, I thought it would be an interesting topic to explore.”

The substandard rebuilding of a local dam in central Pennsylvania to provide the South Fork Fishing and Hunting Club, whose members included Andrew Mellon and Henry Clay Frick, with a lake caused the disaster. After a foot of rain fell in less than 24 hours on May 31, 1889, the dam gave way and released 20 million tons of water. The Great Flood, as it became known, killed more than 2,200 people and caused $17 million dollars in damage (more than $470 million today).

“When people in power can ignore or redact or relax the rules and you’ve got the potential for extreme environmental conditions, disaster can ensue,” Roker says. “Today we have a relaxation of rules about how people can build and how high. Given population density, relaxation of wetland restrictions, and our changing environment, I think it’s a recipe for potential disaster.”

It was the Johnstown flood that also put the Red Cross on the map, Roker explains. “When [the flood] happened,” he says, “they were just getting their act together. People underestimated Clara Barton, which worked to her advantage. She was able to work her way in from the outside and blew everybody away with the organization and its discipline. They were like an army, and established housing, bedding, hospitals, morgues—creating a second city to care for the folks displaced and injured by this horrendous environmental disaster.”

Roker is excited to be at BookExpo. “I hold authors in such high esteem,” he says, adding, “I just wish my mom could be here. One of the things that gave me great pleasure while she was still alive is that she came to a couple of my book parties, and she said, ‘That’s my boy, he wrote this.’ ”