• The Mississippi: A Visual Biography by Quinta Scott

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Low Water on the Mississippi and Thebes Gap

Thebes Gap:

Alexander County, Illinois

“Here is a vast ledge of rocks, which stretch across the river in a direct line. The best channel in the middle of the river, in which place in low water, there is not more than six feet over the rocks.”–Zadoc Cramer, 1814

Rock Formation in the Middle Mississippi at Thebes Gap, 2006

Rock Formation in the Middle Mississippi at Thebes Gap, 2006

The Mississippi is running very low. After the Flood of 2011, the river drained away very quickly and the rain stopped. By the Summer of 2012, we in the Midwest were well into the Drought of 2012 and the river was showing the effects. Now in January 2013, the Upper Mississippi is frozen and the system of locks and dams is retaining water north of Alton, Illinois. On the Missouri a similar system of dams is retaining water in South Dakota and too little water is flowing into the Mississippi to maintain water levels for the 9-foot navigation channel on the Middle River.

Look at any aerial photograph of the confluence of the Missouri and Mississippi. The muddy Missouri spews a flume of silty water into the relatively clear Mississippi. They flow side by side downstream--the Missouri on the west, the Mississippi on the east--for several miles. During the very cold winter of 2000-2001 it was possible to see this phenomenon from the Illinois bank near the spot where Lewis and Clark started their journey up the Missouri: Lock and Dam 26 at Alton trapped ice coming down the Mississippi. South of the dam the river flowed free of ice, but ice did flow out of the mouth of the Missouri. At the confluence the two rivers, the icy Missouri and the ice-free Mississippi flowed side by side in the Mississippi channel.

Look at any aerial photograph of the confluence of the Missouri and Mississippi. The muddy Missouri spews a flume of silty water into the relatively clear Mississippi. They flow side by side downstream–the Missouri on the west, the Mississippi on the east–for several miles. During the very cold winter of 2000-2001 it was possible to see this phenomenon from the Illinois bank near the spot where Lewis and Clark started their journey up the Missouri: Lock and Dam 26 at Alton trapped ice coming down the Mississippi. South of the dam the river flowed free of ice, but ice did flow out of the mouth of the Missouri. At the confluence the two rivers, the icy Missouri and the ice-free Mississippi flowed side by side in the Mississippi channel. In the Winter of 2013 too little water is spewing out of the Missouri to feed the Middle Mississippi.

 Thebes Gap is the geological break point between the Upper Mississippi and the Lower Mississippi. The Upper Mississippi flows through a rocky gorge from Minneapolis to Thebes Gap. South of there the Lower Mississippi meanders across an alluvial plain.

At the beginning of the glacial age, the Lower Mississippi flowed along the western valley wall through an alluvial floodplain in the Western Lowlands along the Black, White, and St. Francis Rivers.

From The Mississippi: “Geologists have speculated that the river abandoned its alluvial valley and diverted through Thebes Gap, a narrow bedrock canyon in the Benton Hills, through the series of glacial floods at the end of the Wisconsinan age. At the beginning of the twenty-first century, seismologists questioned why the Mississippi would abandon its comfortable alluvial valley to ream a new course through bedrock. They noted that fault lines in the Benton Hills were active 10,000 years ago, and speculated that an earthquake along fault lines in the Benton Hills opened the canyon that is Thebes Gap. Glacial River Warren, which broke out of a glacial lake that covered northern Minnesota and North Dakota and reached north into Canada,  thundered through it, and deposited a classical alluvial fan at the mouth of the canyon.”

 “Thebes at the head of the Grand Chain and Commerce at the foot of it were towns easily rememberable as they had not undergone conspicuous alteration. Nor the Chain, either–in the nature of things; it is a chain of sunken rocks admirably arranged to capture and kill steamboats on bad nights.–Mark Twain, Life on the Mississippi

Thebes Gap, where the Mississippi takes a wide turn into the narrow reach of Thebes Gap.

Thebes Gap, where the Mississippi takes a wide turn into the narrow reach of Thebes Gap.

Mark Twain knew Thebes Gap, and while it is no longer killing steamboats, this winter modern tows can’t get through this narrow gorge between the Upper Mississippi and the Lower Mississippi.

The U.S. Army Corps of Engineers have contracted with Newt Marine and Kokosing, a marine engineering firm out of Iowa and Michigan,  to remove the rocks from Thebes Gap. When they are done there on January 11, they will move on to Grand Tower.

A tow steams passed Tower Rock at the beginning of December.

A tow steams passed Tower Rock at the beginning of December.

The river level today at Chester, Illinois is -0.6 feet, which means it is possible to walk out to Tower Rock and see just how low the Mississippi is.


[i]             Cramer, 173; Harrison, Richard W., “Report on Investigations of the Benton Hills, Scott County, Missouri, in Midwest Friends of the Pliestocene, 42nd Annual Meeting, 19-21 May 1995, 7.3; Harrison, Richard W., “Mid-Continent Urban Corridor Mapping Project,” USGS Project No.: 7160-11, U.S. Geological Survey, http://erp-web.er.usgs.gov/reports/annsum/vol40/cu/harrison.htm; Elfrink, Neil, “Gujarat Analog Response,” Archives of Central U.S. Earthquake Hazard MailList, March 21, 2001, http://clifty.com/hazard/archives/1010302-021954.html; Guccione, Margaret, “Re: ‘Gujarat Analog,’” Archives of Central U.S. Earthquake Hazard MailList, Feb 16, 2001, http://clifty.com/hazard/archives/1010216-111758.html.

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Low water on the Mississippi and Missouri Rivers Threatens Navigation on the Middle Mississippi below St. Louis, Part 1

The Jefferson Barracks Reach of the Middle Mississippi, where the river is wide and shallow and causes the Corps of Engineers no end of headaches. July 2012.

We in the midwest have had a terrible drought this summer and even though we have had some rain since the beginning of August, that rain has not flowed to the Mississippi River. The river is very low and navigation is threatened.  And navigation on the Middle Mississippi depends on water flowing from the Missouri. Let’s start with the Missouri, which in normal years supplies the Middle Mississippi south of St. Louis with 60% of its water. This year the Mississippi has drawn 78% of its water from the Missouri.

Low water at the Confluence of the Mississippi and Missouri Rivers, between the west bank and Duck Island, 2009.

Governor Jay Nixon has asked the U.S. Army Corps of Engineersto trash its plan to reduce the amount of water it releases from 17,000 cubic feet per second to 12,000 cfs from the Gavins Point Dam in South Dakota in order to maintain water levels for navigation on the Middle Mississippi. He fears economic catastrophe is the Middle Mississippi River has to be closed to navigation for want of water from the Missouri.

Gavins Point Dam at Yankton, South Dakota

This morning, the flood gage at St. Louismeasured 0.1 foot, Over the next several days it is projected to go up, and down and then way down to -0.6 feet. Any closing could happen when the Mississippi reaches -5 feet at St. Louis.

The Middle Mississippi at Tower Rock just south of Perryville, Missouri.

When the gage at Chester, Illinois gets down to about 1 foot, it is possible to walk out to Tower Rock, just south of Perryville, Missouri. The gage at Chester was a 2.4 feet this morning, which means you cannot walk out to Tower Rock without getting your feet wet.

In the late winter and early spring and extending through the summer of 2003, the Mississippi was so low it was possible to walk out to Tower Rock, south of Perryville, Missouri. Once the flood gage at Chester gets down to about 1.0 foot, it is possible to make the hike.

Should the river fall below 5 feet at St. Louis the Corps of Engineers would consider blasting away rock formations in the bed of the river at Tower Rock and at Thebes Gap.

Update: On the bright side of the drought: with less water running off the land, fewer nutrients are making it to the river, and the dead zone in the Gulf of Mexico has shrunk this years.

The Confluence of the Mississippi and Missouri: A Model Restoration Project

Confluence of the Mississippi and Missouri Rivers, from the Lewis and Clark Memorial on the Illinois Side of the Mississippi

I spent thirty years trying to get to the Confluence of the Missouri and Mississippi Rivers. I drove there, I rode my bike there, but I never quite reached it. I always found myself lost in a farmer’s corn field. Thanks to the Flood of 1993, the folks who farmed this frequently flooded land gave up and sold the land to the State of Missouri for a park on the north side of the Missouri River and a conservation area on its south side.

Until a few years ago the Confluence of the Mississippi and Missouri Rivers was a deep, dark secret. Impossible to get to. There was no way to get there on the Missouri side of the Mississippi. The only way to see it was to find your way to the old Lewis and Clark Memorial on the Illinois side of the river, and even then it was difficult to locate where the Missouri actually streamed into the Mississippi on the opposite side of the river. I was lucky in the very cold winter of 2001 to see ice stream out of the mouth of the Missouri and into the ice-free Mississippi, where ice was trapped behind Lock and Dam 25.  From there I could see how the two rivers flow side by side in the Mississippi channel, the Missouri on the west, the Mississippi on the east.

Mud Flows out of the Missouri at its Confluence with the Mississippi

If you were lucky and could fly low over the Confluence, you could see how Missouri River mud flows on the west and the relatively clear Mississippi flows on the east.

From The Mississippi: A Visual Biography:

“Two refuges overlook the confluence. On the south bank of the Missouri the Missouri Department of Conservation purchased the 4,318-acre Columbia Bottoms in 1997, after the 1993 flood overtopped a levee and washed sand and debris over prime agricultural fields. The department opened the new conservation area–recreated shallow wetlands and bottomland forests with a viewing stand on the bank–in 2002. The State of Missouri acquired 1,121 acres for a state park in 2001 on Mobile Island, built a short wheelchair-accessible walk to Confluence Point, and planned to restore the wetlands and prairies of the natural floodplain behind it, using native trees and plants.”

Confluence of the Missouri and Mississippi as seen from Edward and Pat Jones State Park on the north side of the Missouri River.

From the Edward and Pat Jones State Park you can dip your toe into the Missouri on the right side of Confluence Point or into the Mississippi on the left. And you can see how the Missouri rushes out of its mouth a roils the relatively placid waters of the Mississippi.  Come flood time this park is closed, but when it is open it is a short trek along a wheelchair accessible walk to the tip of Mobile Island.

Confluence, Columbia Bottoms, South Side of the Missouri

Only in the most severe floods is the Columbia Bottoms Conservation Area with its observation platform closed.

School field trip at the Columbia Bottoms Observation Platform

There is more to the Columbia Bottoms Conservation Area than the observation platform. When the river is down, it is possible to descend the bank into the Duck Island Side Channel. Anglers have known of this place since the Missouri Department of Conservation opened the refuge to visitors in 2002. Maybe, some of them had better luck than I and knew how to get there before the refuge opened in 2002.

Anglers fish from a mud flat at the Confluence at Columbia Bottoms

Once down on the mud flats,  it is possible to hike the training structures that prevent the Missouri from flowing into Duck Island Chute.

Dike or Training Structure in Duck Island Chute

And it is possible to hike Duck Island Chute itself.

Duck Island Chute

The conservation department has restored the floodplain at Columbia Bottoms to fields and wetlands and built a terrific visitors center at the entrance to the refuge.

Columbia Bottoms Slough

Finally, on the Illinois side of the river, the State of Illinois has built a museum and a reproduction of Lewis and Clark’s Camp DuBois from which they launched their expedition up the Missouri River in 1804 at the Lewis and Clark State Historic Site.

Reproduction of the Lewis and Clark boat at the Museum in Hartford, Illinois

Perhaps, it is for all these reasons that the U.S. Department of the Interior has named the Missouri and Mississippi Rivers Confluence Restoration Project on of the eleven model projects in the America’s Great Outdoors Rivers program. The restoration project is the work of 40 agencies, both public and private, to the benefit of migratory birds and other wildlife, and we humans.