Businesses and neighborhoods near Addicks Reservoir in the Houston area flooded as a result of unprecedented rains across the region. (David J. Phillip/Associated Press)

The sprawling neighborhoods of brick homes, man-made lakes and walking paths in this area west of Houston always have been considered high ground. When the city has flooded, friends and family would flee here to escape, as many did in recent days during Houston’s descent into disaster.

But that changed Tuesday, when dozens of rescue helicopters swooped in to airlift the elderly and children from rooftops in neighborhoods with lofty names like Grand Mission Estates and Cinco Ranch. Federal Emergency Management Agency officials from as far as California were zipping up their life jackets to perform search and rescue missions alongside volunteers on water scooters, urgently moving people out of a basin that was suddenly — and unexpectedly — filling with water.

Days of unprecedented rains from the remnants of Hurricane Harvey caused the Addicks and Barker reservoirs to exceed their capacity. Addicks, one of two major flood-control reservoirs in the Houston area, spilled over its banks for the first time in history Tuesday morning — this, despite efforts to prevent such “uncontrolled” overflow the day before, officials said. The other reservoir, Barker, to the south of Addicks, is expected to begin overflowing Wednesday, similarly endangering residential areas that are not typically prone to inundation.

With the reservoirs filled, the channels leading from the Katy suburbs have backfilled, leaving no place for stormwater there to go.

“We never thought this area would flood,” said Jessica Wang, 34, whose family had given shelter to relatives and friends after their Houston homes were overcome by water earlier in the week. Drenched and standing in flip flops, Wang hugged a family friend who was in tears. “It’s just shock, a frozen panicked feeling. I feel a mix of fight and fear all at the same time.”

Evacuees make their way though floodwaters near the Addicks Reservoir on Tuesday. (David J. Phillip/Associated Press)

The group of eight was again seeking higher ground when Wang saw on the news that the nearby Barker Reservoir was beginning controlled water releases amid hopes of staving off bigger threats of flooding neighborhoods near the dam. Officials here — acting on lessons learned from Hurricane Katrina, when dams and levees collapsed — want to avoid a catastrophic dam failure that would send massive amounts of water into downstream communities.

On Tuesday, residents navigated water that came up to their chests, some holding pets and soggy wedding and birthday party photographs. The elderly were too afraid to move, Wang said. Others streamed into a makeshift shelter set up at a massive Kroger grocery store.

“It’s hard to say what’s going to happen now with this storm,” Wang said. “Every time I say, ‘no it won’t happen,’ it happens.”

Wang, whose eyes were red, said she hadn’t slept Monday night, huddled with friends, snacking on old chips and glued to their phones, waiting for the water to seep in. They left their home as neighbors around them started to be airlifted out by helicopters.

A soldier with the Texas National Guard driving a high-water vehicle said that about 400 people and pets were rescued by his team of 14 soldiers and five trucks on Monday, with more piling in Tuesday.

“If they can fit on, we’re carrying them out,” he said.

Many families moved to these exurbs of Houston for a small piece of the American Dream, coming from nearby Louisiana and from as far away as Mexico and India to live in 4,000-square-foot homes with double garages and spacious back yards.

But making the flooding situation tougher is the fact that much of the development is new and built on former marshlands, rice farms and cow pastures. The pavement, roads and parking lots have left water with nowhere to go, said Jason Mckey, who lives in the flooded Canyon Gate neighborhood. He even started a business that works to restore wetlands.

Residents wade through floodwaters near the Addicks Reservoir. (David J. Phillip/AP)

The irony “wasn’t lost on me,” he said, putting on his duck-
hunting waders as his friends got their boat ready again. He spent Tuesday morning rescuing neighbors who he said “had no preparation, no flood insurance, nothing. . . . It’s mostly elderly people in just a horrible way.”

Mckey said fatigue was starting to set in because he had been helping people until 3 a.m. and was back at it again at daybreak. He said he saw things “that would make any man cry.”

“It’s just a lot of elderly in dire straits, caught in water they can’t get themselves out of in their kitchens or even bathrooms,” he said. “It’s not quitting time yet — not even close.”

His own home was flooded, and he wasn’t sure where he would sleep.

Lori Roberson, 25, and her husband, Ryan, were just about to close on a new home — four bedrooms, 3½ baths — in a new section of a nearby subdivision here called Seven Oaks. Now it’s flooding with the rest of the neighborhood.

She said they will have to negotiate with the company from which they are buying it to fix all the damage. Fortunately, she said, the new house requires flood insurance because it’s near a gully.

“Flood insurance sounds wise these days,” she said. “It’s just unbelievable.”

Other residents peered with dismay at the neighborhood’s man-made lakes, which still had columns of water spurting upward into the rain.

“And the fountains are still going,” said Gloria Strayhorn, a retired interior designer who was out for a walk with her husband, Bill, who retired from the nuclear industry. They said the lakes were refurbished this spring, “and the subdivision spent so much money setting up these real cute benches,” she said. “And now look.”

Wang reported from Washington.