In 1936, after nearly two decades of devastating floods in the Mississippi River Basin, Congress passed the Flood Control Act, which funneled over $300 million into dams and other projects that engineers hoped would prevent millions from losing their homes in the next flood. But even this dramatic injection of cash left people vulnerable to floods in Ohio. That's when a visionary with the U.S. Army Corps of Engineers pitched a crazy idea: Why not create a vast, scale model of the Mississippi River, as an entire river system, and use a huge system of hydraulic pumps to simulate floods and flood prevention techniques?


The result, in the mid-1940s, was one of the most incredible — and most successful — experiments in hydraulic engineering ever constructed. It was called the Mississippi River Basin Model, and you can still see its remains in Vicksburg, Mississippi.

Over at Design Observer, landscape architecture professor Kristi Dykema Cheramie has a fantastic article about the model's construction, as well as how it affected public policy around flood control. During the horrific floods of the 1920s and 30s, the common response by engineers was to dam areas that had been affected. But their approach didn't account for the complexity of the river and all its tributaries. One dam would be built, but then floods would gush into a new region, leaving millions homeless.


There had to be another way. Cheramie explains the origins of the Mississippi River Basin model:

As construction began on control structures throughout the Mississippi River Basin, and as floodwaters rushed into the Ohio River Valley in January 1937, a district engineer in Memphis, Tennessee, Major Eugene Reybold, raised concerns about this approach. Although the scope of flood control had expanded beyond the Mississippi, the work was limited by current field research methods; engineers found it difficult to track what was being done at various points along the river and thus impossible to predict how isolated "solutions" might affect one other. To understand the Mississippi River Basin as a dynamic system of interconnected waterways, the Corps needed new, more sophisticated scientific tools. Reybold came up with a radical idea: a large-scale hydraulic model that would enable engineers to observe the interactive effects of weather and proposed control measures over time and "develop plans for the coordination of flood-control problems throughout the Mississippi River Basin."

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Instead of pumping money into expensive dams and levees that might not work, the government gradually came to understand that modeling a river system before building constraints on it could save money later. And so, after seeing a smaller model that Reybold had built, Congress gave him the funds he needed for his ambitious Mississippi modeling project.

Because most military human resources had been sent overseas for World War II, Reybold used Italian and German POWs to build his 200-acre model that included the Mississippi River as well as its major tributaries, the Tennessee, Arkansas and Missouri Rivers. The results, as Cheremie puts it, "encompass[ed] 41 percent of the land area of the United States and 15,000 miles of river." She continues:

The prisoners cleared the site of a million cubic yards of dirt and rough-graded the land to match the contours of the Mississippi River Basin. To ensure that topographic shifts would be apparent, the model was built using an exaggerated vertical scale of 1:100 and a much larger horizontal scale of 1:2000. While the existing topography offered a close approximation of the actual Mississippi Basin, some areas required significant earthmoving; the Appalachian Mountains were raised 20 feet above the Gulf of Mexico, the Rockies 50 feet. An existing stream running east-to-west provided the model's water supply. The streambed was molded to take on the shape and form of the upper reaches of the Mississippi, and a complex system of pipes and pumps distributed water throughout the model; it was regulated by a large sump and control house sited near what would become Chicago, Illinois. To simulate flood events, Reybold needed to introduce large volumes of water over short periods of time, so he designed a collection basin and 500,000-gallon storage tower system at the model's edge. Small outflow pipes at anticipated data collection points channeled excess water to 16 miles of storm drains.


And it worked. Using this model, engineers were able to simulate accurately — for the first time — where flooding would occur, depending on where rainfall and runoff started. A new age in civil engineering and disaster prevention had begun. And indeed, this era continues to this day, when engineers use large models to simulate everything from tsunamis and earthquakes, to landslides and floods.


Cheremie eloquently describes this sea-change in how hydraulic engineering was done:

The model had allowed the Mississippi River Basin to become, for the purposes of study, an object, a manageable site. Here engineers, community leaders and civilians could gather to discuss the potential ramifications of particular flood control measures and forecast likely scenarios. Each gallon of water passing through the model was the equivalent of 1.5 million gallons per minute in the real river, meaning one day could be simulated in about five minutes. This allowed for a tremendous capacity to collect data, to use the model as an active tool for communication, and to distribute information about the river as a system. With mayors from cities up and down the river gathering in the observation tower to watch the Mississippi cycle through an entire flood season, it became possible to find edges, limits and centers, to see how and where the river might strike next.


It wasn't so much that the river had been tamed, but that it had become something we could examine rationally. And the disasters it caused could be planned for in a much more deliberate fashion. Ultimately, this would save the taxpayers millions of dollars, because dams and other systems could be build where they were needed — instead of blocking the areas that flooded in previous years, willy nilly, the engineers could plan for novel situations and divert the water intelligently to minimize damage. Sadly, the model today is in ruins, though it was once so well known that it became a tourist attraction in the 1960s. But its contours remain, snaking mysteriously across a Mississippi field, testimony to the importance of predictive models in engineering — and the power of science to help us mitigate natural disasters.

You absolutely must read Cheremie's incredible article via Design Observer

Photos via US Army Corps of Engineers, Andrew Morang, and Kristi Dykema Cheramie




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