Lower Mississippi River

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Lower Mississippi River
Aerialvkbs.jpg
The Lower Mississippi River
Towboats, barges and ships near New Orleans.
Origin Cairo, Illinois (confluence of Ohio River and Upper Mississippi River)
Mouth Gulf of Mexico
Basin countries US
Length 1600 km (1000 mi)
Source elevation 96 m (315 ft)
Main article: Mississippi River

The Lower Mississippi River is the portion of the Mississippi River downstream of Cairo, Illinois. From the confluence of the Ohio River and Upper Mississippi River at Cairo, the Lower flows just under 1600 kilometers (1000 mi) to the Gulf of Mexico.[1] It is the most heavily travelled component of the Mississippi River System.[2]

Levees on the Lower MIssissippi River.[3]

Unlike on the upper rivers, there are no locks or dams on the Lower Mississippi. The river is, however, constrained by levees and dikes to control flooding and secure a navigation channel for barges.[4] The Old River Control Structure, the Bonnet Carré Spillway, the Mississippi River – Gulf Outlet Canal and other man-made structures on the lower reaches of the river seek to manipulate the flow of water in the vicinity of New Orleans.[5]

The political and engineering focus in the 20th century was to separate the Lower Mississippi River from its floodplain. Levees and channelization—along with substantial loss of bottomland forests to agriculture in the alluvial valley—have resulted in a loss of wildlife and fish habitat, decreased water quality, and an expansion of the hypoxic zone in the Gulf of Mexico. Agricultural runoff has resulted in increased turbidity, siltation, pollution from pesticides, toxicity to aquatic organisms, oxygen depletion and eutrophication.[6]

Navigation[edit]

Channel depth of 9 feet is maintained by the Corps of Engineers from St. Louis to Batton Rouge, Louisiana.

Oil tanker on the Lower Mississippi

On the lower Mississippi, from Baton Rouge to the mouth of the Mississippi, the navigation depth is 45 feet, allowing for container ships and cruise ships to dock at the Port of New Orleans and bulk cargo ships shorter than 150 foot air draft to fit under the Huey P. Long Bridge and traverse the Mississippi to Baton Rouge.[7] There is a feasibility study to dredge this portion of the river to 50 feet to allow New Panamax ship depths.[8]

See also[edit]

References[edit]

  1. ^ Bragg, Marion (1977). Names and Places on the Mississippi River. Vicksburg: Mississippi River Commission. 
  2. ^ "Waterborne Commerce Statistics Center". Navigation Data Center. Retrieved 2006-03-12. 
  3. ^ "The Mississippi River & Tributaries (MR&T) Project". United States Army Corps of Engineers. Retrieved 2011-05-19. 
  4. ^ "The Mississippi and Its Uses". Rock Island District Engineers. Retrieved 2006-03-12. 
  5. ^ "The Mississippi River and Tributaries Project". US Army Corps of Engineers. Retrieved 2006-03-12. 
  6. ^ "Background on Lower Mississippi River Basin". EPA: Mississippi River Basin & Gulf of Mexico Hypoxia. Retrieved 2006-04-02. 
  7. ^ http://www.mvttc.com/news_details.php?id=182
  8. ^ http://www.dredgemag.com/June-2015/Corps-to-Study-Lower-Mississippi-River-Deepening-Project/