Monday, August 8, 2011

St. Louis District Corps of Engineers: Navigating the River

Barges move through the Mississippi River.
Transporting cargo by water has historically played a major role in the lives of humans. The navigation of ships and other vessels within waterways is essential to commerce and quality of life.

The U.S. Army Corps of Engineers maintains navigation waterways throughout the United States much like road crews maintain highways.The Corps of Engineers is responsible for ensuring safe, reliable, and sustainable movement of vessels through the nations inland and intracoastal waterway system.
The St. Louis District is responsible for maintaining a navigation channel nine feet deep and 300 feet wide on 300 miles of the Mississippi River from Saverton, Missouri, to Cairo, Illinois. The District is also responsible for maintaining a navigation channel on the lower 80 miles of the Illinois River as well as the lower 36 miles of the Kaskaskia River. The St. Louis District is strategically situated at the crossroads of three major river systems, and is located at the critical transition point on the Mississippi River where it is a “locking river” north of St. Louis and the “open river” from St. Louis on south.

The "Stairway" of water.
The Upper Mississippi River; best described as the stretch of the river from St. Paul, Minnesota, to the river’s confluence with the Missouri River. Dating back to the late 19th and early 20th centuries, this stretch of the Mississippi River was unreliable during periods of low water.  The Upper Mississippi River had a shallow and swift current, rock ledges, small waterfalls, and uncharted shoals and sandbars. These hazards made the river too treacherous to navigate safely. 

In 1930, Congress authorized the Corps of Engineers to create and maintain a 9-foot navigation channel on the Upper Mississippi River through the construction of the slack-water navigation system. As a result, the Corps of Engineers constructed a series of locks and dams on the Upper Mississippi River. As they were completed, the pools formed up river of each dam structure, thereby raising water levels to insure an adequate depth for the navigation channel. These structures, in essence, form an aquatic staircase some 670 miles long from St. Paul to St. Louis

The combined waters of the Missouri and Mississippi Rivers typically assure adequate depths for navigation, except for periods of prolonged drought. Still, much effort is needed to facilitate navigation in the open river, usually in the form of maintenance dredging and regulating works. Maintenance dredging operations involve the repetitive removal of naturally deposited sediment from the navigation channel. 

The St. Louis District Applied River Engineering Center uses table-top “micro-models” to develop innovative solutions to various sedimentation problems. More often than not, these solutions are found in what we call “regulating works”. Regulating works are structural designs, such as chevron dikes, bendway weirs, off-bankline revetments, and notched dikes. By necessity, our river engineers seeks to implement structural designs that work in harmony with the natural laws of the river to solve problems involving sedimentation, erosion and biological diversity, all while providing a safe and dependable navigation channel.

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