Last August, when a freak storm unexpectedly dumped three times more water on Louisiana than did Hurricane Katrina, John Bridgers got his twenty-and-a-half-foot bass boat out. He lives in Watson, a town of nine hundred people northeast of Baton Rouge, which was battered by thirty-one inches of rain during a storm that barely registered outside the state. Bridgers knew help was coming from the Coast Guard, the state Department of Wildlife and Fisheries, and other agencies, but it wouldn’t be enough. “We’re all sportsmen around here,” he said. “Pretty much every other person has a boat. So we got going.”

Bridgers started a Facebook group called Cajun Navy 2016, after the famed all-volunteer flotilla of Louisiana boatmen and women who were credited with rescuing more than ten thousand people during Katrina. Over the next several days, Bridgers’s volunteers used jon boats, motorboats, bass boats, and even canoes to rescue people from flooded homes and pluck them off rooftops. Thirteen people lost their lives, but local media said that the death toll would have been higher if it weren’t for volunteers like the Cajun Navy 2016. “When you pull up to an individual’s house and they’re wading out of five feet of water with a duffel bag over their head, and you pull them into your boat, you realize that’s all they’ve got in that moment,” Bridgers told me, on Sunday. “That stays with you, for good and bad.”

This weekend, as Hurricane Harvey barrelled toward Houston, Bridgers and about three dozen Cajun Navy 2016 members loaded up their boats and hit the road on the four-and-a-half-hour drive to Houston. About twenty made it to the western edge of the city, but traffic and flooding prevented them from getting closer. They called Bridgers and other members and urged them to wait. Bridgers pulled over at a truck stop, settled into his seat, and logged onto Facebook. He put out the word out that the Cajun Navy 2016 Facebook page, which has fifty thousand followers, could help coördinate volunteer efforts. “Please Like and Share the page so that we can again make a difference during yet another disaster,” he wrote. Pleas for help started rolling in as people told Bridgers where their grandparents, neighbors, and kids were stranded. “Two Adults lady is 7 months pregnant,” one post read. “3 lil ones under the age of 4,” another said. “Two elderly in 80s, One in wheelchair. 1 Adult...2’ of water in house right now,” another read. One message said that several senior citizens were “sitting in water chest deep” in a nursing home. Bridgers hoped that a volunteer or first responder might get wind of the message and head for a home they might otherwise have missed. None of this was possible during Katrina, in 2005, he noted, when Facebook was primarily used by college students, and volunteers had to be onsite to help save lives. “Say, during this whole ordeal, you help a thousand people this way—you would have helped a lot,” he told me.

Late Sunday afternoon in Houston, the mayor, Sylvester Turner, said that local police and fire officials had received six thousand calls for rescue, and more than a thousand people had successfully been saved, many plucked from roofs and attics. Turner said that 911 operators had received more than fifty-six thousand calls since the storm began. “We have not been able to keep up with all of the 911 calls that are coming in,” he said at a briefing. “But it is our intent to respond and to take in anyone that calls.” The official death toll stood at five, but it was unclear what was happening in large parts of the city, or whether the situation would worsen as flooding intensified.

Television-news anchors warned viewers to stay out of attics where they could be trapped by rising water—or to bring an ax so they could hack a hole in the roof and climb out to safety. Officials said that Houston, the country’s fourth-largest city, had already suffered billions of dollars in damage, and that it would take years for the metropolitan area, home to six million people, to fully recover.

The governor of Texas, Greg Abbott, said that three thousand National Guard members were helping hundreds of local police and firefighters carry out rescues. Sixteen helicopters and six hundred water vessels criss-crossed the city. Unlike during Katrina, when New Orleans residents were told not to attempt boat rescues on their own, some government officials in Texas were encouraging it. The police department in League City, just south of Houston, put out a call for private citizens with flat-bottom or shallow-water boats to lend a hand. The department was quickly overwhelmed with offers of help.

“We literally have hundreds of names and numbers and not enough manpower to go around,” the department posted, on Facebook. “If we do not contact you please do not think that we do not appreciate your offer. We are simply overwhelmed with the number of offers for help.”

The local ABC affiliate posted video of volunteer motorboats maneuvering around submerged vehicles on a badly flooded street in Dickinson, Texas. A Fox affiliate broadcast video of a volunteer rescue boat that had taken on stranded people in Friendswood, including several small children weighed down by large backpacks, and a woman carrying a baby on her chest.

Offers of assistance poured in from as far away as Philadelphia, but Louisianans, in particular, vowed to help. Bridgers, the Cajun Navy 2016 organizer, and other Baton Rouge-area residents said they remembered how the Texas National Guard mobilized during Katrina, and recalled the donations sent by Texans after last year’s flood. “It’s more of a reciprocal gift of love back to them for what they did for us last year, plus we know they need it,” a Baton Rouge woman who was organizing a supply drive to a Houston church told the city newspaper, the Advocate. “How many times has Louisiana been in the crossfire, and how many times have people from other places helped us?”

As the sun set on Sunday, it was impossible to know how many Texans trapped by flooding had been rescued and how many remained in danger. An estimated four hundred billion gallons of water had engulfed the Houston area, and rain was expected to continue for days. Bridgers planned to keep posting on Facebook all night in hopes of spurring more rescues. When the water recedes and the camera crews move on, he told me, his crew’s real work would begin. A year after the devastating flood in his Louisiana town, Cajun Navy 2016 is still helping coördinate volunteer efforts to rebuild homes. Bridgers plans to use the group’s Facebook page to pitch in with Houston’s rebuilding effort, too. “Once that water’s gone, they’re not gonna have homes to go to,” he said. “I can relate, ’cause I’ve been there.”