Stone Riffles to Control Stormwater on American Bottom

The Stone Riffle Pilot Project was launched on Monday at a groundbreaking ceremony at Miner Park in Glen Carbon, the first of four riffles planned for the park and the first of 58 riffles planned in the Metro East region of Southern Illinois.

The four riffles will be placed in Judy Creek, which winds through the park. Frank Miles, administrator of the Madison County Environmental Department, said at the groundbreaking that 18,000 tons of sediment flow through the creek each year.

Judy Creek in Miner Park, Glen Carbon, Illinois (Photo by Armand Coniglio)

Some people describe a riffle as a low-water dam of stone.

At the groundbreaking, U.S. Army Corps of Engineer Col. Tom O'Hara described a riffle as, "kind of like a speed bump, to slow down that water and, more importantly, to stop the sediment in that water.

Riffles raise the water level, slow the water and allow sediment to precipitate out of the stream down to the stream bed.

"It's kind of like a speed bump we put in the path of the water to slow down that water and, more importantly, to stop the sediment in that water," O'Hara said.

Gary Clark, director of water resources for the Illinois Department of Natural Resources, said at the groundbreaking that engineers across the country are looking for "comprehensive, holistic solutions" to managing stormwater.

The four Miner Park riffles will cost about $90,000, officials said. The money will be contributed by federal, state and local sources.

The overall floodwater reduction plan for the state, which includes the other 54 riffles and other measures proposed by the U.S. Army Corps of Engineers, would cost $200 million, Kniep said. The plan has been delayed since 2004 awaiting funding.

The money comes from federal, state and local sources, Miles said. The Corps of Engineers will provide technical support. Miner Park was chosen as a demonstration area because it provides easy access to Judy's Branch Creek, a major drainage element, officials said. The creek was selected because of the amount of water that flows through the creek into the American Bottom.

Project manager Michelle Kniep told officials at the groundbreaking that riffles are a step toward solving a "systemic problem" by slowing the runoff speed. Fast-moving water can cause creek banks to erode, washing the riparian soil into the creeks.

Miles said, "The riffles that will be constructed will slow the rate of stormwater flow through the creek and detain sediment that would otherwise fill drainage in the American Bottom."

The American Bottom flood plain of the Mississippi River covers about 175 square miles bounded on the east by a nearly continuous, 200-300 foot high, 80 mile long bluff of limestone and dolomite, above which begins the great prairie that covers most of the state. Most of the flood plain is protected from flooding by a levee and drainage canal system. The riffles are intended to relieve pressure on that drainage system.

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