NEW ORLEANS — Hurricane Francine quickly strengthened before making landfall in Louisiana on Wednesday, leaving hundreds of thousands of people without power. flooding of a cemetery and dumping rain on New Orleans, a city that relies on a uniquely intricate network of canals and pumps to drain its water.
In some areas, more than 7 inches (18 centimeters) of rain fell, which overwhelmed the drainage system. In some places, the water rose quickly, forcing an emergency room nurse to save a pickup truck driver minutes before his vehicle was submerged.
“Effectively, the swamp of centuries ago is coming back to life, and the communities built on those drained lowlands are getting water in their homes and cars” during major storms, said Richard Campanella, a professor at Tulane University’s School of Architecture and author of the book “Draining New Orleans.”
New Orleans was shaped by flooding and has long struggled to keep homes dry and the water out. Residents were warned to conserve water to ease the strain on the sewer system, though drinking water was never affected. Officials said Thursday that they had drained the rain, but the job requires an immense amount of infrastructure that is vital to keeping New Orleans habitable.
Here’s why the city is facing downpours and how authorities are combating flooding:
Hurricane Katrina showed how bad it can get. A breach in the levee flooded most of the city, stranding residents on roofs and killing nearly 1,400 people. Pumps worked for weeks to pump out the floodwaters.
Then the federal government more than $14 billion invested on a massive 133-mile defense system of levees, pumps and other infrastructure designed to keep the water out. Hurricanes create storm surges that those walls are supposed to hold back, and Francine didn’t come close to challenging the design. Initial estimates of storm surges on the Lake Pontchartrain shoreline were about 3 to 5 feet.
“The walls at that location were about 16 feet. We had a lot more room,” said Ricky Boyett, a spokesman for the Army Corps of Engineers.
But when there is a dense ring of earth, concrete and steel around the city and surrounding areas, it also keeps the rain in and that is a problem.
Simply put, much of the city is below sea level. Working against it is gravity, which helps most of the city’s sewer systems drain water to nearby wastewater treatment plants, lakes, and rivers.
This requires moving water uphill, primarily to Lake Pontchartrain, north of the city.
New Orleans sits just up the Mississippi River from Louisiana’s swampy southeastern coast. It’s a region shaped by the Mississippi River, which deposited sediment that formed strips of high ground surrounded by dense, swampy lowlands. But building New Orleans meant designing the river and keeping water out. That kept the river from depositing new sediment, said Boyce Upholt, author of “The Great River: The Making and Unmaking of the Mississippi.”
Now “the city is collapsing under its own weight,” he said.
Francine dumped rainwater inside the city walls. This requires a complex system of pumps and canals. Generally, the system can discharge an inch of water in the first hour and then half an inch every hour.
“When a raindrop falls on the city, it goes into retention basins. The retention basin, a small drainage system, carries that water into larger pipes or canals, and the canals carry that water to individual pumping stations,” said Ghassan Korban, executive director of the Sewerage and Water Board of New Orleans, which manages the drainage system.
When the system is overloaded, the streets are the first to fill up. But homes and businesses can also take on water when the system is overloaded — as happened in the Lakeview neighborhood when Francine died.
Some of the infrastructure the city relies on is old, with some of the pumps dating back a century, though those pieces have been refurbished over the years.
The infrastructure is vast — some of the canals could fit in a bus. There are 24 drainage pumping stations and 99 large pumps. But the aging pumps run on an outdated electrical frequency, requiring additional equipment to adapt them to modern power generation.
Campanella said reliable power at the right frequency is one of the system’s vulnerabilities.
“Because they are pumps, they require electricity, and that’s where it gets tricky,” Korban said.
When Francine arrived, some of the pumps were having electrical problems, slowing down drainage in some places.
The drainage system has undergone several improvements over the years. After severe flooding in 1995, federal projects added new pumping stations and upgraded others, while miles of canals were added. A major rainstorm in 2017 led to significant management changes at the agency that manages the drainage system. Officials also built ponds to catch rainwater and worked to improve the reliability of the power supply.
At a news conference after Francine on Friday in Baton Rouge, Louisiana Gov. Jeff Landry said the drainage system had improved over the years, but there was more work to be done. The Republican said state and federal emergency officials were working with the city to determine where pumps and power generation are needed.
“So we can feed the amount of rainfall into a model and more accurately predict what those disasters are going to look like and what resources are needed,” Landry said.
A worst-case scenario is when a storm surprises meteorologists and stalls over the city, dumping massive amounts of rain. Some of the worst flooding the city has seen in recent history was not hurricanes, but large rainstorms.
“You just have to do your best,” Korban said.
Climate change is causing the atmosphere to hold more moisture, increasing the likelihood of large, wet storms.
“Since Hurricane Katrina, we’ve seen a number of events in Louisiana that have really tested existing stormwater drainage infrastructure,” said Dominic Boyer, a professor at Rice University in Houston and co-director of the Center for Coastal Futures and Adaptive Resilience.
“That will only become more challenging as time goes on,” he said.
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Phillis reported from St. Louis. Associated Press writer Sara Cline contributed from Baton Rouge, Louisiana.
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