Climatologists & Hydrologists: Today's MS River Floods A Whole New Animal Compared to 20th Century
The swollen, churning, unrelenting river that's flooding towns from Minnesota to Louisiana this month is not Mark Twain's Mississippi River. Sure, there were big floods during the 20th century, including historic tides in 1927, 1937, 1965, 1973, 1983 and 1993. But the spring floods of 2019 — which experts generally agree are the most damaging in 25 years — are among a new generation of Mississippi River crests that bear only passing resemblance to the floods of distant past. Experts say the new floods come faster and more furiously than their 20th-century counterparts. They last longer and are less predictable. And they cause more property damage, especially in the basin's upper reaches where wetlands, forest and prairie have been replaced by subdivisions, office parks and drain-tiled farm fields.
"As Dorothy said in 1939, 'Toto, I have a feeling we're not in Kansas anymore,'" said Gerald Galloway, one of the nation's leading experts on Mississippi River hydrology and a professor of civil and environmental engineering at the University of Maryland, where he is an affiliate of the Center for Disaster Resilience. Galloway would know. In 1994, as a brigadier general in the Army Corps of Engineers, he led the interagency committee charged with identifying the root causes of the 1993 Mississippi River flood and proposing a long-term approach to floodplain management.
The 1994 panel, reporting to Vice President and future climate activist Al Gore, identified several key steps the federal government should take to reduce future flood risk: First, increase spending on levee repair, maintenance and security; second, improve coordination among federal, state and local authorities who oversee the river and its floodplain; and third, foster engagement with floodplain residents, farmers and businesses about how to mitigate risk from rising water. "Twenty-five years later, we're still having the conversations. Unfortunately, not much has changed in the way we go about our business on the river," Galloway said last week. As Gilbert White, a pioneer in U.S. natural hazards research, used to say, "'The half-life of the memory of a flood is remarkably short.' Once it's past, we get back to regular business where potholes seem to eclipse levee failures," Galloway said. But where policy changes have been static, physical and environmental changes to the river have been ongoing. The climate is becoming warmer and more volatile, exacerbating known risks and creating new ones to the river's environmental, social and economic health.
The most recent National Climate Assessment, for example, states that worsening flooding on U.S. rivers has caused "more long-term interstate freeway closures, while high and low extremes in water levels in the Mississippi River and other waterways have disrupted navigation and commerce." Over the 21st century, between 5,000 and 6,000 bridges will be compromised from unprecedented flooding, while "increases in rainfall intensity can accelerate bridge foundation erosion and compromise the integrity and stability of scour-critical bridges," the NCA said. Communities may have little choice but to adapt, relocate or die, as the cost of living with chronic riverine flooding goes well beyond what many communities can afford.
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