Along the Mississippi River in Vicksburg, Mississippi, the U.S. Army Corps of Engineers maintains a vast complex of metal huts the size of warehouses. Inside is a remarkable series of working models of dams, levees, even beaches. These are not playthings. The scale models are used to solve civilian and military problems with waterways all over the world.
One working model represents a dam, spillway and navigational locks in Oregon at a scale of 1:55. One meter on the model equals 55 meters at the actual damsite on the upper Columbia River.
Research hydraulic engineer Chuck Tate says the assignment here is to improve the survival rate of salmon that spawn on the river. "We've got problems of both adult salmon that are going upstream and juvenile salmon going downstream," he says. "They each have their set of problems, and their survival has been impaired somewhat by the dam. So we're trying to improve those survival characteristics."
Those problems for the salmon include running into the spillway's turbines that produce electricity for the surrounding eastern Oregon and Washington region. At best, the turbines buffet and bruise the fish; at worst, they pulverize the salmon. Another problem is the steep and exhausting climb that salmon face at the spillway as they head upstream to spawn. In that regard, the Corps of Engineers creates the very situation it is now addressing when it dams free-flowing rivers.
Whatever the root of the problem, scientists here in Mississippi are studying ways to ease the salmon's journey. They're testing miniature deflectors and what are called "fish ladders."
"It doesn't have rungs where they get out and go hand over hand. But it's a series of small rapids, small jumps for fish to make," explains Mr. Tate.
But why is the scale model necessary? Why not just conduct the research in the field, at the spillway itself? Chuck Tate says there are several reasons.
"You're working with very fast water flow, very rough surface conditions, a lot of aerated flow. And you can't get in there. We cannot hold instruments in there. ... They get destroyed. In the model we've got something that's small, that's controllable. ... You can get to places on the model that we can't get to on the prototype, simply because it's too dangerous to go there."
And Mr. Tate points out that working with models is a lot cheaper than doing the experiments at the river itself. "These models are expensive, but to go out and do some of that kind of work in the field is also extremely expensive."
At other models in other buildings here in Vicksburg - some of them top secret - U.S. Army Corps of Engineers scientists are looking to solve problems with beach erosion, hurricane survival, and tactical military situations. Right here, Chuck Tate and his colleagues keep tinkering with the miniature spillway in hopes of giving salmon a better chance to survive in the wild. It is R&D, research and development, with very real applications.