Rivers & Flood Control

HISTORY OF THREE RIVERS

The Atchafalaya River is a distributary of the Mississippi, but this developed over a period of time. The two rivers have an interesting history that includes people trying to merge the two, resulting in three rivers that meet in the area known as Old River.

  • BEFORE THE 15th CENTURY: The Red River and Mississippi River were separate rivers, more or less parallel.
  • 15th CENTURY: The Mississippi River turned west and a loop, later called Turnbull's Bend, formed. It intercepted the Red River, which became a tributary of the Mississippi River and the Atchafalaya River was formed as a distributary of the Mississippi River.
  • BY 1778: The entrance to the Atchafalaya River was occluded by a logjam.
  • 1831: Capt. Henry M. Shreve, founder of Shreveport and a world-renowned river engineer, dug a canal through the neck of Turnbull's Bend, thus shortening river travel time.

Over time, the north section of Turnbull's Bend filled in with sediment. The lower half remained open and became known as Old River and linked the three rivers.

LOCKS & DAMS – CONTROLLING THE WATER

In the late 19th and early 20th centuries, huge floods along the Mississippi River increased the size of the channel and the carrying capacity of the Atchafalaya River until concern mounted that it might capture most of the flow and redirect the Mississippi again. Congress directed the US Army Corps of Engineers (Corps) to build a control structure that would allow restriction of the flow down the Atchafalaya River to 30% of the total flow down the Mississippi and the Red Rivers. The 70-30 split, as it came to be known, was approximately the breakdown of the flow in the 1950s and was thought to be a reasonable choice that would allow the Mississippi River to maintain its current route. The Corps completed the first elements of the control apparatus in the 1960’s.

In 1973, a large flood threatened to destroy the main control structure and the Corps began a redesign of the control system to include additional structure elements. The resulting “Old River Control Structure” (ORCC) that exists today was designed and built to allow as much as half of the combined flow of the Rivers to be diverted down the Atchafalaya during a major flood and to allow configuration of the flow to minimize stress to the structures.