Climate Change Increasing Flood Risks As Louisville's Protection Decays
In the frigid January days ahead of the Great Flood of 1937, rain and sleet battered Louisville. The Ohio River swelled until its banks disappeared and floodwaters lurched into the city streets.
Canoes with flood refugees paddled into the foyer of the Brown Hotel on the corner of Fourth Street and Broadway as waters lapped against the roofs of homes in the western part of the city; even the water on the track at Churchill Downs was more than knee-deep.
In total, the deluge inundated more than two-thirds of the city. Modern modeling suggests a catastrophic flood today would look nearly identical, according to the Metropolitan Sewer District.
Now, of course, a 29-mile system of walls, levees and pump stations stands between the city and the next great flood, but that system is deteriorating. And as the planet warms, severe storms are becoming more common across the region, increasing the risk a catastrophic flood could again swell the banks of the Ohio River and arrive at Louisville’s doorstep.
‘Worse than Katrina’
Louisville’s flood protection system is among the largest in the country, in terms of the number of people it protects. The oldest sections were built between 1947 and 1956, and protect downtown and parts of west Louisville. In various places, it’s made of concrete walls, earthen levees and pump stations designed to move water outside the walls during flood events.
Metropolitan Sewer District flood protection supervisors say many of these stations still rely on designs and parts from the 1950s. About half are in need of upgrades to electric equipment, few have backup power supplies and none of the system’s 16 pump stations were designed to handle increased flows caused by severe storms. Nor were they designed to handle the increased runoff from all the additional pavement and asphalt across the city.
Even the seemingly-sturdy concrete floodwalls could be compromised if there was a severe enough flood. If waters rise within four feet of the top, some areas of the walls don’t meet minimum safety factors set by the Army Corps of Engineers. Others use the same designs that failed during Hurricane Katrina. In some places, the concrete used in construction of the floodwalls and pump stations is cracking, peeling and flaking.
“Even the concrete inside the building is, I mean you can dig your fingers into it an inch deep, it’s just, you know, it’s just really bad,” said Metropolitan Sewer District flood protection supervisor Dane Anderson about the Paddy’s Run Pump Station, near Rubbertown.
Louisville’s floodplain runs a half-mile to five miles wide along the Ohio River, extending from the southwest of the county to downtown and continuing northeast along the river, including parts of Butchertown, Portland, Shawnee, Old Louisville, Shively and Valley Station.
If a catastrophic river flood happened today, it could affect more than 200,000 residents and as much as $34 billion in property, according to the Army Corps of Engineers.
This worst-case scenario threatens Louisville’s energy grid, transportation, schools and hospitals. It could swamp Superfund sites and industrial chemical facilities like those in Rubbertown.
The sewer district has outlined a plan to spend $4.3 billion on critical infrastructure; $683 million of that would go to the flood protection system for repairs and upgrades. But so far, the sewer district hasn’t gotten approval to raise user rates enough to fund the plan.
In the meantime, Flood Protection Supervisor J.P. Carsone is coordinating with an alphabet soup of federal, state and local agencies to make a catastrophic urban flood plan.
“I can tell you the impacts to Louisville would be worse than what Hurricane Katrina was to New Orleans,” Carsone said. “And that’s not me just trying to scare people, that opinion is shared by the people working on this plan.”
Climate Change Brings Increasing Flood Risks
The planet is warming and it’s already making weather in the Ohio Valley more unpredictable. That variability increases the risk of droughts and heatwaves, as well as heavy rains and flooding, according to the 2017 Ohio River Basin climate report by the U.S. Army Corps of Engineers.
But overall, it’s expected to get wetter in Louisville and that will increase the frequency of flooding events.
This is something that Jim Noel with the National Weather Service’s Ohio River Forecast Center said is already happening.
“The Ohio River at Louisville didn’t hardly have any floods between 1964 and 1997,” Noel said. “And since 1997 we’ve had several pretty good floods, like 2018.”
As of mid-October, the city was on track to have its wettest year ever — nearly 21 inches above average.
For the next two decades Louisville can expect to see more frequent flooding like the first half of the 20th century, Noel said. That frequency increases the risk the city could repeat the Great Flood of 1937.
That year, the Ohio River crested at 52.15 feet on January 27. Louisville historian Tom Owen said the water covered about two-thirds of the city and drove about 200,000 to evacuate.
“My wife’s family, my family were all refugees from the flood,” Owen said. “The water filling the sugar bowl, on the shelf above the sink in the cabinet would have been six feet deep in the kitchen. Bear in mind we are talking about January, February, so we’re talking about icy, brown, muddy floodwater.”
The city’s second-worst river flood was only eight years later in 1945, peaking at 42.1 feet. Overall, the city has seen more than a dozen major Ohio River floods in the 19th and 20th centuries.
Between 2040 and the end of the century, the extra precipitation across the region is forecast to cause Ohio River maximum stream flows to rise as much as 35 percent, according to the climate report. That increases the risk flooding would exceed the historical range.
But the problem is that today’s stormwater and flood protection systems are designed based on historical data and modeling, said Vanderbilt University engineering professor Janey Camp.
“The issue is we’re seeing storm events we didn’t necessarily plan for,” she said. “We shouldn’t rule out the potential for large-scale flooding on managed river systems in the future.”
The Problems With Louisville’s Flood Protection System
Today, Louisville's flood protection system includes 16 pump stations and 29 miles of walls and levees. There are also approximately 150 floodgates and 79 closures where teams would have to place sandbags or gates to stop encroaching floodwaters.
The system is one of the largest in the country in terms of what it protects, but remains untested against a major river flood. Because of that uncertainty, the Army Corps Levee Senior Oversight Group considers the system to be “high risk.”
“[LSOG] considers the risk associated with a failure prior to overtopping to be high based on uncertain performance and the associated consequences of potentially high life loss with extremely high property damage during flood events,” according to the National Levee Database.
The Army Corps of Engineers study found “several deficiencies” during the Corps’ last major review back in 2010, but kept a rating of “minimally acceptable.” The report notes there are limited records for levee and floodwall designs and no information on floodwall stability, foundation bearing capacity and settlement analysis.
Many of Louisville’s 4.6 miles of floodwalls are at least 60 years old. Several have shown signs of cracking, flaking and peeling, though much of that is repaired through regular maintenance. But others need to be totally rebuilt.
“We’re doing a repair project right now because of bad concrete,” Carsone said. “We’re getting rid of a whole monolith in one section, the concrete is in that bad of shape.”
More than 4,000 feet of the city’s flood walls were designed using the same technology that failed during Hurricane Katrina. These “I-walls” can be pushed over as rising water leans against them. Separate analyses found some areas of the concrete floodwall do not meet minimum safety factors, according to the Army Corps.
But in both cases, rising waters would only pose a threat of breaching if they were to rise within several feet of the top of the walls, according to the Army Corps.
And that’s just the floodwalls. Many of the city’s pump stations are in disrepair, too. Corrosion is eating away at parts at the Paddy’s Run Pump Station near Rubbertown, and before February’s floods even began, the Beargrass Creek Pump Station already had one pump down. It lost another during the flooding — both due to mechanical issues.
At the far end of the system, the sewer district has problems with every single pump at the Pond Creek Pump Station, which protects Fairdale and nearby communities.
“We’ve got four pumps out there and all four pumps have issues right now,” MSD’s Dane Anderson said. “I worry about that part of town, because if something happened we would have issues right now.”
The News Isn't All Bad
So what, exactly, does Louisville’s flood protection system have going for it?
It’s got really high walls, which is great because that’s the most common way flood protection systems fail. In fact, Louisville’s floodwalls and levees were built three feet higher than the crest of the 1937 flood, which was a 500-year flood event.
It would take an even rarer flood event for water to spill over the walls, Carsone said. And that’s less likely to happen because of flood reservoirs the Army Corps has put in place upstream along the Ohio River.
Also, Louisville’s levees are made from clay, which is superior to sand, he added.
Metropolitan Sewer District regularly inspects and maintains its floodwalls, levees and pump stations. Teams regularly practice installing flood closures on a rolling basis; every closure is practiced at least every three years.
The sewer district is also working proactively to make a catastrophic urban flood plan, which should be complete in the next two years. That will help inform city plans in case of a breach, including who to evacuate and where to set up emergency response.
The U.S. Army Corps of Engineers is also working on its own feasibility study to better understand the state of the flood protection system. In the meantime, the Corps conducts annual inspections.
If a major river flood were on its way, Louisville residents would likely know well in advance thanks to monitoring by the United States Geological Survey and others.
But keep in mind, the age and complexity of the flood protection system increases the chance of failure, Carsone said. And it only takes one breach.
“In a flood event, most people in the community don’t have to give it a second thought,” Carsone said. “I think we do our jobs very well, we do protect the city. The bad side of that is people don’t realize the risk.”