Mississippi River Flooding: Can We Move Past 1928?

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Published on July 19th, 2011  |  Discuss This Article  

Before the Mississippi River flood of 2011 gets swept out of our memories by the torrent of the endless news cycle…can we talk about the success story about flooding on the Mississippi that was too easily overshadowed by the more dramatic natural-disaster imagery and rhetoric?

In the flood’s wake, dozens of opinion pieces connected the flood to the country’s mismanagement of its rivers, floodplains and wetlands. (Here’s one from The New York Times.) While I may agree with the major points made in some of those pieces, it’s more useful to focus on what worked — and how we can build on it for even better river management.

First, a historical comparison: The 2011 flood carried more water than the epic 1927 Mississippi River flood, but did infinitesimally less damage:

  • In 1927, dozens of levees broke, an area the size of South Carolina was inundated for months, 700,000 people were displaced from their homes and officially hundreds (and more likely thousands) of people died.
  • In 2011, none of the levees in the Mississippi flood system failed, damage and disruption was miniscule relative to 1927, without any loss of life (note I’m talking about the flood on the Mississippi, not the more recent flood on the Missouri River).

Why such dramatically different results? Because of differences in how the river and floods were managed between now and back then. In 1927, the river was managed without coordination, like a car company in which the manufacturing plants didn’t communicate with either their upstream parts suppliers or their downstream dealers. Just as a company managed this way could never produce optimal performance, this disjointed flood-management system was not up to the task.

Today, the Mississippi is managed as a comprehensive system. As a direct response to the disaster of 1927, the Army Corps of Engineers transformed the piecemeal efforts at managing the Mississippi into the Mississippi River and Tributaries Project (MR&T), coordinating levee construction and maintenance, dam operations, and navigation for thousands of river miles of the Mississippi and its major tributaries.

Importantly, the comprehensive system also included a set of “floodways,” areas of historic floodplain that could be reconnected to the river during high flood events, allowing floodwaters to spread out and reduce pressure on levees.

This approach — letting the floodplains do some of the work — proved critically important in 2011.  In 1927, the river was entirely confined by levees. Although flood management at the time lacked coordination, it did share an underlying faith that the entire floodplain could be walled off from the river. Initially denied access to its floodplain, the surging river eventually found the weak spots and obliterated both levees and the “levees only” paradigm of flood management.

But just because the river is now managed as a comprehensive system doesn’t mean there isn’t room for improvement. Imagine that hypothetical, and disorganized, car company pulling its act together such that its suppliers, manufacturers and dealers are now seamlessly integrated. Great — except that the company still only makes gas guzzling V-8s because it hasn’t researched changes in market preferences over the last 50 years. The system is effectively producing cars, but cars that reflect a too narrow set of objectives.

While managing the Mississippi as a system was visionary for 1928, that vision reflected that era’s values, expectations and knowledge. What’s needed today is a modern vision of a comprehensive system — we now want hybrids and all-electrics in addition to muscle cars (and maybe through design and engineering advances, those muscle cars can evolve out of gas-guzzler status).

What I mean to say is that management of the Mississippi should continue to evolve to produce a broader set of objectives. The MR&T was designed essentially only for flood control and navigation. But today we have so much more science about the interrelationships of rivers and floodplains and the full benefits floodplains provide.

For example, when flooded, floodplains can be extremely productive areas to support river fish populations and can recharge groundwater and remove nutrients from the river. Because of this, floodplains can be part of the solution for reducing the enormous “dead zone” that forms each year where the Mississippi disgorges water laden with excess nutrients into the Gulf of Mexico.

The 2011 flood demonstrated that allowing the river to access its floodplain in strategic locations is critically important for reducing pressure on levees and keeping people safe. But given that the frequency of large floods appears to be increasing, are the current set of floodways sufficient — or do we need to build more “relief valves” into the system?

Floodplains act as relief valves in two ways:

  • First, they expand the area available to move floodwaters safely through a particular stretch of river. This is analogous to opening up more lanes at a bridge toll crossing during rush hour to manage intense traffic.
  • Second, floodplains can perform what’s called “peak shaving” — reducing the height of the flood peak experienced at some downstream point. For this, imagine a floodplain as a parking lot alongside a major freeway. During a particularly heavy period of traffic, a large number of cars exit the highway and park in the lot, staying there until traffic ebbs. The highway “downstream” of the parking lot will experience lower peak traffic because of the cars parked in the lot.

For years, environmentalists have advocated that rivers be managed as comprehensive systems and that floodplains be reconnected to rivers to keep people safe from floodwaters. Management of the Mississippi is far from perfect, but environmentalists should not hesitate to call attention to the fact that comprehensive management and floodplain “relief valves” were essential tools for keeping people safe in 2011.

But scientific understanding and societal expectations continue to evolve, as does the mighty river. An updated vision for comprehensive management of the Mississippi can produce a much broader set of values and ensure continued safety under changing conditions.

(Image: 1927 flooding in Cary, Mississippi. Image credit: jwinfred/Flickr through a Creative Commons license.)

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