River model could help solve silting problem

When the Mississippi River drops to about 10 feet on the Cape Girardeau gauge, silt deposits make launching a boat at the Red Star River Access difficult, if not impossible.

For recreational boaters, that can be an inconvenience. But the ramp is also used by the Cape Girardeau Fire Department's water rescue team, and the inability to get a boat in the water could quickly make a bad situation much worse for someone stranded on the river.

At the U.S. Army Corps of Engineers River Engineering Lab in St. Louis today, corps scientists will be meeting with invited guests to view a model representing a seven-mile stretch of river in front of Cape Girardeau. While the meeting technically isn't about the problems of silting on the Missouri side of the river, the data gained from running the model could help solve it, hydrologist Leonard Hopkins said.

Over the centuries, the Mississippi River's main channel has meandered across the floodplain, and because the corps has had responsibility for maintaining navigation, the changing channel has required a lot of dredging at times to keep it open, he said.

In 1992, with the channel hugging the Illinois side of the river as it goes past Cape Rock, the corps constructed a series of submerged rock structures to train the river to maintain the channel it occupied.

"What that has done is fixed the channel along the left bank, which is great for navigation but wasn't so great for the sand plant or the boat ramp," Hopkins said.

Today's meeting is designed to study environmental improvements along the Missouri shore. The corps isn't required to prevent the deposit of sediments in front of the boat ramp, Hopkins said, but it is responsible for improving the environmental health of the river. The model could indicate a way to do both, he said.

"If there is something alternative that can be done to improve things in that reach for habitats, a side benefit could be increased depths for anything along the right bank," he said.

The model will test whether notches in dikes, the use of chevrons or other structures could force the river to build islands, Hopkins said. The islands would split the river's flow, forcing faster water against the Missouri bank and scouring out some of the sediment.

"It is our plan to plant the seed and improve things through this stretch of the river," Hopkins said.

Guests who have been invited to attend include Mayor Jay Knudtson, fire chief Rick Ennis and members of the Honkers Boat Club. The boat ramp used to be known as Honker's Landing before it was acquired by the Missouri Department of Conservation.

At a meeting of the Mississippi River Commission, Tom Holzhauser of the boat club asked for action. "When the river drops below 10 feet, you can't get a boat out there," he said.

Along with studying the Cape Girardeau stretch, today's meeting will also review models of an eight-mile section of the river near Thebes, Ill. The issue in that area isn't silting, Hopkins said, but a rocky river bottom that provides little or no habitat for fish and wildlife.

In that area, Hopkins said, the corps will study making notches in existing control structures or adding structures to the river to encourage the creation of small islands that will provide cover for wildlife and slower water for fish.

rkeller@semissourian.com

335-6611, extension 126