The Great Flood of '93: a watershed event for river history, flood policy
When bleary-eyed David R. Busse plugged the latest river levels and rain forecasts into his hydrology calculations in mid-July 1993, he came to a startling conclusion: The floodwaters surging down the Mississippi and the Missouri rivers would converge in St. Louis at the highest level ever recorded.
“There were many so-called experts telling us that those kinds of levels weren't possible,” recalls Busse, now the chief of engineering and construction at the Army Corps of Engineers' St. Louis District. “But I remember telling the colonel: ‘It looks to me like not only are we going to set an all-time record, but we will be over it for a very long time.’”
Busse turned out to be on target. The Great Flood of '93 washed away the river-level records for St. Louis — the metropolis at the watery bull's eye where the Big Muddy meets the Father of Waters — as floodwaters overtopped levees across the Midwest, caused more than $15 billion in damages, destroyed or damaged 50,000 homes, caused 54,000 people to be evacuated and inundated 6.6 million acres along the two great rivers and their tributaries.
The 1993 flood also became a watershed event for floodplain management, with some of the lessons learned from the deluge exerting influence far beyond the Midwest. A big lesson — reinforced later by Hurricane Katrina's swamping of New Orleans levees in 2005 — is that no levee is invulnerable, and planners should focus more on assessing risk than completely preventing damage.
“There is no such thing as absolute protection” from floods, says river engineer Gerald E. Galloway, who led the White House-appointed panel that drew lessons from the Great Flood of 1993. “That's why the world is moving to flood risk management.” That “residual risk” approach is based on the recognition, he says, that “everybody's got to recognize that if they live in the floodplain, they can't be promised immunity from floods.”
As the lead author of the 1994 Galloway report, “Sharing the Challenge: Floodplain Management into the 21st Century,” Galloway called for a comprehensive approach to “flood damage reduction” — as opposed to strict flood control — that would deploy both structural (such as levees) and non-structural (such as wetlands and floodplain restrictions) tools. Recognizing that completely clearing floodplains is unrealistic, the report suggested striking a balance among the many competing uses of the river, with government, businesses and private citizens sharing more responsibilities.
While some of those recommendations were heeded, many others were not. “In 1994, we said the upper Mississippi and the Missouri represented an amalgam of all sorts of loose confederations,” Galloway told the Beacon in an interview. “They are not tied into each other, there is nobody doing overall supervision. That was a problem, and it remains a problem.”
Galloway, a former Corps brigadier general, is now an engineering professor at the University of Maryland, as well as an international consultant on floodplains and flood risk management. He said considerable progress has been made in bolstering urban flood protection and assessing flood risks. But he added: “There are a lot of things still to be done.”
Could another Great Flood hit St. Louis?
Neither Busse nor Galloway (nor any other river expert) can rule out the possibility that another flood of the magnitude of the ‘93 deluge, or greater, might again converge on the St. Louis region — especially given the possible future impact of global climate change, which may exacerbate storms.
In June, the Federal Emergency Management Agency predicted in a flood insurance report that climate change, combined with the growth in U.S. population and development, “is going to increase substantially the number of acres that will be flooded in this country. There's going to be more water in the rivers, so more areas are going to flood,” said Galloway.
“We may not have as many big storms, but when they come, they are gully-washers. They really come down in a dynamic nature.”
That's the sort of weather pattern that struck in 1993, swelling the upper Mississippi and the Missouri rivers so they reached a record level of 49.6 feet on the St. Louis gauge. Today, the big question is: What would happen if floodwaters converged at St. Louis four feet higher than the ‘93 level? That would be what river engineers call the “design flood” — the river level that the region's flood structures, such as the levees and flood wall, are designed to withstand.
“I'm pretty confident that we could do the same job we did in ‘93” in protecting St. Louis from severe flooding when the river gauge hits 50 feet, said Busse. After all, the Corps has replaced gates on the city's flood wall and improved levee systems on the Missouri side. “We have better knowledge now of what our levees can and can't do than we did in 1993. That's a good thing.”
Another good sign is that St. Louis — unlike so many of the river towns south and west of the metropolitan area — was not hit especially hard by the 2011 flood and this spring's high water. “The highest river stage at St. Louis was in 1993, the second-highest in 1973. But this spring's floodwaters were also bad, with the river rising to the fifth or sixth highest level at St. Louis,” Busse said.
“Had this spring's flood happened in 1993, it would have been a really big deal to the media and to the people who lived here,” he added. “But because we went through ‘93, we got very little press on this event. There are very few places in the country where you would have had the fifth or sixth highest flood in over 150 years and it would have been a ‘ho hum’ event.”
A bigger threat had been posed by the Great Flood of 2011, which set numerous records along both the lower Mississippi (below Cairo) and the upper Missouri River. It threatened — but mostly spared — St. Louis.
“St. Louis is in the middle, right between the Missouri and the lower Mississippi, and you would have thought we would have record flooding. But they were separated by about one month,” said Busse. “We had a flood, but it wasn't a major flood. The big floods were above us and below us.”
But Busse conceded that a “design flood” in St. Louis might well cause serious problems. “If the question is, ‘Could we withstand the design flood?’ at 54 feet, I would have concerns on the Metro East side,” he said. “The one that would be of the most concern, and the one where we would prioritize resources during a flood-fighting event . . . is the East St. Louis levee.”
Then again, Busse added, there is a big difference between the design flood and what happened in 1993. “Four feet [higher] is a really big deal,” he said. “You remember in ‘93 how it just took forever for the water to keep coming up. It had to keep raining and raining and raining to do that.”
It is no surprise to officials in the Metro East region that the Corps has not yet certified some of their levees. That's why Madison and St. Clair counties approved a sales tax increase and formed the Southwestern Illinois Flood Prevention District Council to manage a $160 million levee improvement project in the Americans Bottoms area, with the goal of getting the Corps to approve the levees.
But Galloway cited the Metro East region as one where the residual risk approach could be helpful. “We're not going to abandon East St. Louis. There is a tremendous amount of industry in the area,” said Galloway. “But if you believe the flood risk management paradigm,” even if Metro East gets to the 500-year flood level of levee protection, “they still have to worry: ‘Will we be prepared for the chance that it never stops raining and we have water coming over the levees?’”
“There are things you can do to make sure it doesn't cost you an arm and a leg. Some people call this resilience, others call it preparedness,” said Galloway. “That's what we've got to be thinking about. With less money and an uncertain future, we're got to be prepared for all eventualities.”
Less money at the federal and state level is, indeed, a wave of the future in floodplain management. “National flood policy has evolved since the 1993 flood,” said Samatha Medlock, policy counsel for the Association of State Floodplain Managers. “There is an increased emphasis on state and local government roles. Ultimately, land use and planning decisions related to flood plains are made at the local government level.”
That is true in the St. Louis region, in areas from the Metro East to the Chesterfield region. In the latter, the devastation caused by Missouri River levee breeches during the ‘93 flood led officials to raise funds to build the mammoth Monarch Levee, which has opened the way for extensive floodplain development.
But Galloway cautions that even giant levees aren't flawless, especially if a perfect storm strikes the Midwest. “There is no such thing as a levee that can't be overtopped,” he said.
“But it's going to take a very big flood to overtop the Chesterfield levee. Does that mean we know what that's going to be?” With climate change, he said, “we are now in new territory.”
Next: Environmentalists have raised concern about flood policy and river management since the Great Flood.
Editor's note: Robert Koenig won the National Press Club's top award for Washington correspondence for his analysis at that time of the government's response to the 1993 flood.
View Historical crests in a larger map
Markers for regional river gauges show which gauges have seen record levels this year. Red markers represent a 2013 flood stage in the top 5 of all time. Yellow markers represent a 2013 flood stage in the top 10 of all time. Green markers represent gauges where 2013 river levels have not made the top 10.