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Environment

A Mighty Model

Big science does the Big River justice.

By Ernie MastroianniMay 15, 2018 5:00 AM
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Ernie Mastroianni

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In a cavernous building in Baton Rouge, Louisiana, just steps from the Mississippi River, environmental engineer Clint Willson lifts a beaker filled with dark plastic crumbs. They look like black lava salt, but in this room, the granules are a stand-in for river sediment. The tiny particles are an essential part of the massive Lower Mississippi River Physical Model: a working, flowing simulation of the river.

The model, bigger than two basketball courts — with bleachers — elicits gasps from first-time visitors. Carved into the surface of a huge white table is a precise re-creation of 14,000 square miles of southeastern Louisiana, gleaned from more than 4 billion data points. A deep winding channel crosses the entire model, representing 179 miles of the mighty Mississippi from just south of Baton Rouge to the delta. Projectors beam satellite views onto the table, turning the white surface into a photorealistic replica of the terrain, and real water moves the artificial sediment, mimicking how the river moves sand.

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The green area shows the Mississippi River drainage basin. (Click to enlarge) | National Park Service

Researchers are using this model to find ways to stem alarming land loss in the lower Louisiana bayou. Nearly 1,900 square miles have disappeared since the 1930s, when hundreds of miles of levees went up in response to the Great Flood of 1927, one of the nation’s worst.

“The river, before the levees were put in, acted like a garden hose that was left unchecked,” says Jason Lanclos, deputy executive director of Louisiana’s Coastal Protection and Restoration Authority (CPRA), which funded the model. “The river would basically spray everywhere across the coast and deposit sediment, fresh water, and continue to build land on top of land. You put levees around the river system and you have no more of that.” The land washes away without constant replenishment from the wild river; another 2,250 square miles or more could drain away over the next 50 years.

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At the model’s upriver entrance is an acoustic gauge that measures the height of the water in the simulation. The location of this and other gauges match those placed in the real river by the Army Corps of Engineers, so model operators know exactly how close their water level matches the level of the river on a given date. Roads are elevated lines, and the elevated rectangles are fertilizer and ammonia plants. | Ernie Mastroianni

To help restore some of that lost land, CPRA has proposed eight sediment diversion structures — high-tech gates in the water that would release slurries of replenishing soil into the bayou — along the lower Mississippi. But where they should go is hard to pin down. This giant model will give researchers a powerful tool to understand river dynamics, sediment movement and how planned diversion structures will affect one another.

Though numerical models and computer simulations are valuable, the physical model generates a steady stream of data that fills in digital gaps. It allows CPRA to investigate different scenarios to see how the river responds not just in one year, “but really five, 10, 25, 50 years into the future,” says Willson, the Louisiana State University professor who heads the research. Big as it is, the model is still just a small piece of a 50-year, multibillion-dollar master plan for coastal restoration.

By The Numbers

Cost

  • $18 million for model, displays and building

Dimensions

  • 120 feet by 90 feet, simulating 14,000 square miles

Scale

  • 1 foot equals about 1 mile

  • 50 hours of the model’s run time equals 50 yearsof real-world river time

Components

  • 1 mile of steel support beams

  • 20-inch-thick concrete slab for base support

  • 20 high-definition overhead projectors

  • 216 high-density foam core panels at 5 by 10 feet, each 700 pounds

  • 864 individual jack stands

  • 6,000 gallons of water to replicate sea level

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