Southeastern Section - 54th Annual Meeting (March 17–18, 2005)
Paper No. 20-2
Presentation Time: 1:20 PM-1:40 PM

GEOLOGY OF GRANT'S CANAL: THE UNION'S ATTEMPT TO BYPASS VICKSBURG, MISSISSIPPI

HARRELSON, Danny W., U.S. Army Engineer Rsch and Development Ctr, 3909 Halls Ferry Road, Vicksburg, MS 39180, danny.w.harrelson@erdc.usace.army.mil.

Grant's Canal was the Union's attempt to bypass Vicksburg by diverting the Mississippi River across a narrow meander neck (approximately 4000 feet wide) known as Desoto Point. The initial canal project was begun by Brigadier General Thomas Williams in early summer of 1862. It was designed to bypass the fortifications at Vicksburg, then the last major stronghold on the Mississippi River. Work on the canal began June 27, 1862, but by July 24, it had stopped and Williams's forces withdrew downstream. The Confederates realized as early as the spring of 1862 that they would have to defend Vicksburg, but their strategists incorrectly assumed that an attack would come upriver rather than downriver. They also erroneously believed that shoaling at the mouth of the Mississippi River and pointbar deposits (sandbars) on the inside of meander loops would prevent any attack by deep draft vessels.

In January 1863, work on the canal was resumed by troops under the command of Major General Ulysses S. Grant and the project became known as “Grant's Canal”. Digging continued into spring, but a rise in the river on March 5th broke thru the cofferdam at the head of the canal and flooded the excavation. The canal immediately began to silt up despite the efforts of two steam-driven dipper dredges, put to work clearing the channel. The dredges, however, were exposed to confederate artillery fire from the bluffs at Vicksburg and driven away. By March 24th Grant had decided to make a bold change in tactics and work on the canal was abandoned.

The canal project failed because of a lack of understanding river geomorphology including proper canal configuration (elevation and shape) to effectively use the river's erosive power to deepen the excavation. Ironically, nature later accomplished what the Grant's troops could not when on April 26, 1876 the Mississippi flooded across Desoto Point (forming Centennial Cutoff) and isolated Vicksburg from the Mississippi River.

Southeastern Section - 54th Annual Meeting (March 17–18, 2005)
General Information for this Meeting
Session No. 20
A Geological Miscellany
Bayview Hotel at the Grand Casino Resort: 5
1:00 PM-4:40 PM, Friday, March 18, 2005

Geological Society of America Abstracts with Programs, Vol. 37, No. 2, p. 46

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