Jameson Island Ephemeral Stream EarthCache
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Jameson Island Ephemeral Stream
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Welcome to the Jameson Island Unit of the Big Muddy National Fish and Wildlife Refuge. This foot bridge was built in the spring of 2006. At that time it crossed an ephemeral stream occasionally dammed by beavers. An ephemeral stream is a stream channel which carries water only after rain or snow-melt and has no base flow component. The dams created by beavers established a beneficial wetland by diverting water into a natural containment area for fish and wildlife habitat.
Since construction, this area has experienced higher annual precipitation and beaver dams were abandoned. This has caused a consistent stream flow subjecting the soil around the piers supporting the bridge to erosion – the weathering and transport of sediment, soil, rock and other particles in the environment and depositing them elsewhere.
The Refuge made several attempts to help control the erosion, but were unsuccessful. In the spring of 2008, the Refuge approached the University of Missouri Civil Engineering Department for some advice on saving the structure.
After several visits to the site with professors and engineering students, they came up with a plan. One engineering student designed a rock weir to catch sediment in the stream and planned rock armoring around the piers and up to the weir to reduce further erosion. This helped build the foundation of soil lost around the bridge piers. Before beginning the project, the surrounding watershed had to be mapped and the sediment transport was calculated.
A watershed is the land area from which surface runoff drains into a body of water, such as this stream. Watersheds are also called drainage basins.
A volunteer team of engineering students and their professor joined Refuge staff members and a local volunteer to move almost 40 tons of ditch rock averaging 6 to 18 inches in diameter and weighing from 5 to 30 pounds. Each rock was placed over a layer of geotextile fabric to prevent erosion. Most of the rock had to be hand-placed using teamwork to pass the rocks.
The finished project will allow the Refuge to utilize the footbridge for many years. The footbridge and associated trail connect the historic town of Arrow Rock, Mo to the Refuge and the Missouri River. The town of Arrow Rock is visited by hundreds of thousand visitors each year. In 2006, it was designated as one of only a dozen distinctive historic destinations by the National Trust for Historic Preservation (NTHP). It was designated a Preserve America Community in 2008.
Eight interpretive signs along the trail help interpret the tie between the cultural history of the town, Lewis and Clark, Santa Fe Trail and the natural history of the Refuge. By taking a right once you cross the footbridge and walking about half a mile, you will reach the Missouri River. About half a mile to the left after crossing the footbridge will take you to our parking lot. While walking on the trail read the interpretive signs and give a short explanation of how the Missouri River has changed from the time of Lewis and Clark, prior to channelization, to the river's current state (e.g. depth, flow pattern, features). E-mail what you find to tim_haller@fws.gov.
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