As New Orleanians recover from floodwaters that inundated the city on Wednesday, residents are preparing for an unprecedented triple whammy this weekend: heavy rain, an already engorged Mississippi River and a tropical storm in the Gulf of Mexico that is expected to make landfall in Louisiana on Saturday, with a storm surge that could reach six feet.

Fourteen years after Hurricane Katrina killed more than 1,800 people and swamped this city, the deluge will be a major test of the updated drains and pumps that remove water from the streets, the earthen levees that hold back the river, and the elaborate system of barriers that prevents tidal surges from sweeping in — all part of a $14 billion investment in the city’s flood-fighting infrastructure.

On Thursday, the National Weather Service forecast that the river would crest at 19 feet, one foot lower than previously predicted, reducing concerns that river levees would be topped or breached. But residents, their memories of Katrina reawakened by Wednesday’s downpour, are still worried about Tropical Storm Barry.

Residents sit under a bus shelter along a flooded Broad Street as heavy rain falls Wednesday in New Orleans. (David Grunfeld/AP)

Louisiana Gov. John Bel Edwards (D), who declared a state of emergency Wednesday, said that expected rainfall “is extremely serious” and the system will “likely produce storm surge, hurricane-force winds and up to 15 inches of rain,” putting the entire state at risk.

He urged residents on Thursday to make preparations, check emergency supplies and monitor directions from local officials. He said he had authorized the state’s National Guard to have 3,000 personnel ready to assist.

“There are three ways Louisiana floods,” he said: storm surge, high river and rain. “We’re going to have all three.”

New Orleans Mayor LaToya Cantrell (D) decided not to evacuate residents, saying evacuations would be triggered by a Category 3 hurricane. Farther south, where the Mississippi meets the gulf, the president of Plaquemines Parish, Kirk Lepine, did issue orders for residents to leave.

Patrice Cheneau has heard for several days that the Mississippi was high and that a new storm was looming.

So on Thursday afternoon, Cheneau walked the four blocks from her house in the city’s Lower Ninth Ward to the Andry Street Wharf — located on the levee that protects her neighborhood — to see for herself just how high the water really was.

When Cheneau saw the river flowing about 10 feet below the top of the levee, her mouth opened in shock.

“And we are still supposed to get 48 hours of rain?” Cheneau, 47, asked as she surveyed the swollen river.

“This has my heart just pumping. . . . I got my babies to worry about,” said Cheneau, referring to three granddaughters visiting from Atlanta.

After a few minutes, Cheneau had seen enough. Despite assurances from the U.S. Army Corps of Engineers that the levee is not likely to be topped, Cheneau said she had decided that she and her grandchildren will ride out the storm at her daughter’s high-rise apartment in New Orleans’s Uptown area.

“I don’t want to get stuck and be like my mother [during Katrina], having to get rescued from the attic,” said Cheneau, a chef who was living in Atlanta during Katrina. “I really feel like the government just don’t care about the people, especially on this side of the canal, but I have my babies that I have to worry about. Forty-eight hours of rain is just scary.”

The new infrastructure, including the world’s largest pump, which can displace 20,000 cubic feet of water per second, has given some water-weary residents some reassurance.

Leonard Flot only needs to glance out his window at a street sign to know his property is vulnerable to flooding here in New Orleans’s Lower Ninth Ward — he lives on Flood Street.

Flot, 60, also recently bought three vacant lots that surround his one-story dwelling because many of his neighbors never rebuilt after 14 feet of water submerged this neighborhood during Hurricane Katrina.

After Katrina, Flot worked as a contractor on some Corps projects fortifying the levees that surround New Orleans. He says he knows from that work that flood defenses are now far sturdier.

“I’m not worried about anything,” said Flot, who now works as a truck mechanic. “I know the Ninth Ward is now protected from flooding . . . I don’t got no reason to run. This is not a Category 4 or 5,” he said.

Matt Harrington boards up a Vans shoe store near the French Quarter in New Orleans on Thursday as Tropical Storm Barry approached. (Seth Herald/AFP/Getty Images)

Derek Boese, chief administrative officer of the Southeast Louisiana Flood Protection Authority-East, which operates and maintains the infrastructure on the east side of the river, said the improvements were striking.

“You can’t compare it to what existed pre-Katrina,” he said, explaining that his team began on Tuesday the laborious process of closing floodgates along the river, which continued through Thursday.

He was confident, he said, that the levees would not breach but was concerned nonetheless about the pressure on them because the river had already been high for eight months and because of the amount of rain forecast.

According to a report issued in April by the Corps, the levees have been gradually losing height because of ground subsidence and sea level rise.

Among the low spots Boese’s team has been evaluating is one in the Corps’ own parking lot.

“They have HESCO baskets going in as I speak,” Boese said late Wednesday, referring to temporary barriers, often filled with sand, that can be placed on top of existing levees.

Retired Maj. Gen. Michael Walsh, who managed the Corps’ response to flooding in 2011 and is now a senior adviser to the environmental consultancy Dawson & Associates, said the combination of threats is unusual.

Typically, the river, fed by snowmelt and spring rains, settles down by May or June, he said, before the hurricane season rolls in. This year, though, the Mississippi has stayed stubbornly high even as Barry gathers strength. The rain further complicates the picture.

“New Orleans is protected from riverine flooding,” said Walsh, “but not necessarily from 18 inches of rain.”

Walsh took the dramatic step of opening the giant Morganza Floodway more than 300 miles above New Orleans in 2011, flooding farms and rural homes in a bid to save the city. Ricky Boyett, a spokesman for the Corps of Engineers in New Orleans, said the Corps is not planning to open the giant spillway this time because the consequences of flooding farmland, homes and oil wells could outweigh the benefits.

Another spillway much closer to New Orleans, the Bonnet Carre, is about half open — the second time this year it has been opened. Boyett said there are no plans to open it further, saying doing so could create a surge in Lake Pontchartrain. The spillway is also releasing runoff from farms upstream rich with nutrients from fertilizer that deplete the oxygen in the water, creating a dead zone in an area usually replete with seafood.

But the biggest challenges so far have been clearing storm drains and keeping the pumps working within the city, half of which lies below sea level.

Emily Vuxton, policy director of the Coalition to Restore Coastal Louisiana, which focuses on reinforcing natural infrastructure such as wetlands and marshes to protect the city from storm surges, was struck by how slowly the giant pumps work.

Wednesday’s downpour inundated areas that had never flooded before, Vuxton said. She was rattled after being stranded for six hours in a parking lot watching other residents canoe by.

“We are all still on edge about whether we should leave or not,” she said.

When Flot woke up Thursday morning and saw predictions of more than a foot of rain and a possible 19-foot flood crest on the Mississippi, he had a nagging feeling that he needed to do something.

He got out his shovel and began clearing the vegetation and silt from the storm drains here on Flood Street, about a quarter mile from a levee that he hopes will keep the Mississippi River off his property.

“People still are scared,” Flot said as he scraped the pavement with his shovel. “A lot of people in New Orleans, and lot of black people in New Orleans, just don’t believe this administration and still feel they have been kicked to the curb and treated badly by everybody.”

But with his 12 children now grown and scattered around the country, Flot plans to just sit in his house and ride out the storm on his couch. He will also be recalling why he taught all of his children to swim when they were about 5 years old.

“My daddy taught me when I was 5, and I taught them, too,” Flot said. “Because my daddy always said, ‘When y’all live 14 feet below sea level, you got to learn how to swim.’ ”