A sporting-goods retailer found itself at the center of the rescue effort in flooded Houston, first opening its stores to rescuers in need of boats, life preservers and other supplies, and then converting its headquarters into temporary residences for hundreds of police and other emergency responders.

As of Wednesday morning, retail chain Academy Sports + Outdoors was hosting more than 400 rescue-team members at its corporate campus west of Houston, with people coming to work in 12-hour shifts from as close as Waco, Texas, and as far away as Connecticut.

Academy employees who were flooded out of their homes have also started to take shelter at work. One of the first to do so: Chief Executive J.K. Symancyk, along with his wife, two children and dog Sammy. They live in a mandatory evacuation zone near the swollen Brazos River and don’t yet know if their house is flooded.

“This was as democratic a catastrophe as could possibly be. It didn’t pick one part of town,” Mr. Symancyk said. The 45-year-old has been Academy’s CEO since November 2015.

Academy has a history of contact with law enforcement because it sells firearms in its chain of 235 sporting-goods stores. Dealing with the Federal Bureau of Investigation and other federal agencies is a daily part of its business. So when the first call came in Sunday from the Houston Police Department requesting flat-bottomed jon boats and paddles, Academy brass weren’t all that surprised.

About 75 flat-bottomed boats are reserved at Academy's offices for rescue efforts this week. The company has already given rescue teams about 125 boats from area stores. Photo: Jeff Bush/The Wall Street Journal

But the calls kept coming. From the Webster Police in Houston’s suburbs to the mayor of Missouri City, another suburb, to the Waco Police, which was sending people down to help. They wanted kayaks, canoes, ponchos and pontoon boats. In many cases, Academy opened the doors of closed stores so first responders could grab what they needed.

As waterlogged evacuees made it to dry land, they needed more. Sleeping bags, air beds, backpacks, fresh T-shirts, socks, shoes and underwear.

Rescuers needed all those goods, too, and a safe, dry place to rest. So Academy opened up its four-story sport-themed headquarters, which hasn’t flooded and still has power. It also has gyms for sleeping and places to shower.

Then the governor’s office called requesting that National Guard members be able to take shelter at Academy because the buildings are between two flooded areas, the Addicks and Barker reservoirs that are spilling water into downtown, and the Brazos River, which is flooding ranch land. Academy opened up its distribution center to get more space.

Joseph Shives and his family are among over 9,000 evacuees from Tropical Storm Harvey that have taken shelter at Houston’s convention center amid the city's flooding. They talk with WSJ about their ordeal and the uncertainty ahead. Photo/Video: Jeff Bush/The Wall Street Journal

Cots and air beds now line hallways and are strung around cubicles in its buildings. On Tuesday, the National Forestry Service staged about 200 buses on the parking lot for evacuations. A mobile surgical unit was set up and 50 ambulances are now on standby, ready to move when they can.

“It started with us being willing, but the logistics have to line up for this to make sense,” Mr. Symancyk said.

That takes food, which Wal-Mart Stores Inc., typically a fierce retail competitor, has donated from nearby stores, he said.

Academy is offering financial assistance for immediate needs like hotels for about 150 employees, but many of the retailer’s 5,500 local staff are trying to assess damage and reopen Academy’s 30 stores in Houston and more around the state.

All told, 125 jon boats have been deployed from Academy stores and another 75 reserved for this week’s rescue efforts if they are needed, Mr. Symancyk said.

Academy is deciding where to donate $1 million worth of clothes and shoes later this week, the CEO said. The Red Cross will likely be one recipient, but he is hearing of other groups, too.

“We’re trying to balance where it can be most useful in the here and now,” he said.

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Write to Lynn Cook at lynn.cook@wsj.com