• The Mississippi: A Visual Biography by Quinta Scott

    "Great book and great blog - thanks for the first book I have seen that addresses the contemporary river, headwaters to gulf." Dan McGuiness, Audubon, St. Paul, Minnesota

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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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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.

The Flood of 2011–Act Two

The Flood of 2011 on the Lower Mississippi is draining away into the Gulf of Mexico. Save for the fact that all that good mud, which could nourish the Louisiana wetlands in Breton Sound and the Barataria Basin, has gone sailing off into the Gulf of Mexico, the Corps of Engineers management of the flood has been deemed a success. The reservoirs on the tributaries of the Mississippi retained water in the uplands until the big river could handle it; the spillways, the New Madrid, the Morganza, and the Bonnet Carre siphoned floodwater off the river and eliminated the possibility of flooding in Cairo, Illinois and New Orleans. The severe drought along the Louisiana coast and in the Atchafalaya Basin dried out the land, and lessened the damage to the land, to homeowners in the protected towns in the Atchafalaya Basin and Western Terrebonne Basin. In short the dry land soaked up the flood that spilled out of the Morganza Floodway.

Which brings us to Act 2 of the Great Flood of 2011: the Missouri River. The St. Louis Post-Dispatch has had a series of articles on flood control on the Missouri River in the last week.

American Bottom after the levee break at Columbia, Illinois, 1993

Remember that during the Flood of 1993 both the Missouri and the Upper Mississippi flooded simultaneously, leading to the collapse of the levee systems on both rivers. During the 2008 flood on the Upper Mississippi, farmers on the American Bottom were grateful that the Missouri was not also in flood, because water was seeping under the levee that broke in 1993.

Well, this year we have serial flooding first from the Upper Mississippi and then the Missouri. So unless we have lots of rain in Minnesota, Iowa, and Wisconsin, we will not have both rivers in flood at the same time below St. Louis.

In the old days, before the construction of the six dams on the upper Missouri river, the river tended to flood twice each year, once in April when snow melted on the prairies and washed into the river and the second time in June when the snow-pack in the Rockies melted and streamed into the river. The Flood of 1881 inundated Niobrara, Nebraska, and the town moved to higher ground. The Flood of 1927 had eased off in the late spring, only to reassert itself with the June rise on the Missouri.

The dams were designed to solve to dual annual floods on the Missouri and for the most part they did. Folks who live along the river put its floodplain to other uses: corn and soybean fields, industrial plants, or starter castles on the banks of the river. All of these are threatened by the June flood rolling down the Missouri. The only creatures who will benefit are the birds and the fish and the people who care about their survival. The flood will enhance the work the Corps of Engineers has done to restore sandbars to the Missouri, sandbars, which provide nesting sites for the endangered Piping Plover and the Least Tern, and side channels for the endangered pallid sturgeon.  The birds may have a hard time this year while their sandbars are under water, but next year, should the dams do the work they were designed to do, should be great.

It’s the management of the reservoirs to mimic the dual floods that once streamed down the Missouri that is causing the flooding problems this year. The reservoirs were almost full in preparation for the “spring rise” before a heavy rain soaked the Missouri River watershed, which filled them to capacity. Now the engineers have to release excessive amounts of water from the reservoirs. That will keep the flood going through August.

Fort Peck Dam, Corps of Engineers photograph

Which brings us to the dams, which also may be endangered. They are old; they are hydraullic fill-read earthen-dams; their floodgates have seldom been opened or have never been opened; the reservoirs behind them are full. And they are holding back a tremendous amount of water. “Earthen dams when overtopped by floodwater, do not stand.” Should the first one go–the Fort Peck Dam, which three miles long–the other five could follow. The Corps of Engineers has expressed confidence in the viability of the dams.

Fort Peck Dam Spillway under construction

All that mud that comes down the Missouri has been deposited behind the dams. So much so that the cattails grow in the still shallow waters behind the Gavins Point Dam at Yankton, South Dakota, where the Niobrara River has deposited sand from its watershed. After the completion of the dam in 1957, the water table at Niobrara rose, flooding basements. In 1969, the town decided to move again. The Federal Government helped pay for the move.

The Missouri River at Niobrara behind the Gavins Point Dam

The problems Niobrara experienced after completion of the Gavins Point Dam are roughly analogous to the problems the Corps of Engineers is experiencing behind Lock and Dam 26 at Alton, Illinois on the Mississippi. Construction of the dam raised the water table and water began seeping under the levee, putting stress on the levee.

When I was writing The Mississippi: A Visual Biography, I tried to figure out why these dams were built. What was their purpose? They were built because the Corps of Engineers could and Congress supplied the funds. They are an extension of the Mississippi River and Tributaries Project, designed to retain floodwaters upstream until the Lower Missouri and the Mississippi could handle them. The Fort Peck Dam and its reservoir are used to produce hydroelectric power, to reduce floods, to enhance navigation, to protect fish and wildlife, to create opportunities for recreation–boating, to irrigated the surrounding prairies, to supply the public with water, and to improve water quality. It’s a tall order.

The Realities of the Mississippi, the Missouri,the Atchafalaya, the Louisiana Coast, and New Orleans

Last week a pair of geologists, at the University of Texas, Austin, proposed diverting the Mississippi and its sediment to Breton Sound on the east and Barataria Bay to the west in order to build new deltas in each body of water.

 

DiversionIllustration

Illustration from Science Daily, (Credit: AGU/EOS)

They would make the diversions about ninety miles south of New Orleans, my guess near Grand Bayou on the west, where the Mississippi levee runs, and Bohemia on the east, where the Mississippi River levee ends.

 

Bohemia

Mississippi River Ridge at Bohemia

Like other who have proposed Mississippi River diversions to build land in Louisiana, they have looked at the landbuilding that is going on at the mouth of the Atchafalaya River and the Wax Lake Outlet from the Atchafalaya Basin. Since the completion of the Old River Control Structure in 1962, the Atchafalaya has funneled off 1/3 of the Mississippi water and sediment at Old River, about 200 miles north of New Orleans. The Atchafalaya also carries all of the Red River and its sediment to the Gulf of Mexico, where it is building new land. Last summer the New Orleans District of the Corps of Engineers announced it would study changing the ratio of Mississippi to the Atchafalaya with an eye to diverting more water and sediment to the Atchafalaya.

It should be noted that the Corps built the Old River Control Structure to keep the Mississippi from diverting to the Atchafalaya on its own in its effort to find a shorter, steeper route to the Gulf of Mexico.

 

OldRiverControl

Old River Control Structure

All of this runs in the face of a paper published four months ago by a pair of geologists from Louisiana State University, stating that there is not enough sediment in the Mississippi to rebuild the Louisiana Coast. It’s all trapped behind dams in the Mississippi River basin, dams designed sometimes to retain floodwater in the uplands until the Mississippi and its tributaries could handle them, and built sometimes because the Corps of Engineers could and Congress approved.

Carl Pope, Executiver Director of the Sierra Club, put all this in perspective in an article at the Huffington Post. He came away from the Ecumenical Patriarch’s Eighth Religion, Science and the Environment Symposium with his own take on the state of the Mississippi River, the Missouri, the Atchafalaya, the Louisiana Coast, and New Orleans: they are all of a piece. The only way we are going to save the Louisiana Coast and New Orleans is to release the sediment, trapped behind dams on the Missouri, which supplied 60% of the mud to the Mississippi in 1900, and allow it to flow down the Mississippi/Atchafalaya and build land along the Louisiana Coast. This sediment is needed to keep up with the rise in sea level, which will come as Arctic ice melts.

To get the sediment to the coastal wetlands, something will have to be done about the levees that keep the Mississippi spilling over into the Louisiana parishes south of New Orleans. And, the river needs more room to flood north of New Orleans, where it is hemmed between levees–that protect cotton, corn, and soybeans–clear to the mouth of the Missouri River and above, where the Flood of 2008 breached agricultural levees in northern Illinois and farmers want a 500-year levee to protect their fields. New Orleans may get a 100-year levee someday.

Copyright © Quinta Scott, 2009, All Rights Reserved

Pallid Sturgeon, the Shovelnose Sturgeon, and Side Channels

The U.S. Fish and Wildlife Service may ban commercial fishing of all sturgeon, the endangered pallid sturgeon and the common shovelnose sturgeon. Fish and Wildlife put the pallid Sturgeon on the endangered list in 1990.

Those of us who love caviar have driven the harvest of shovelnose sturgeon from 6,600 pounds in 1995 to 23,000 pounds in 2007, when its roe or eggs were getting $80 a pound.

There is a problem here: the young pallid sturgeon can be mistaken for an adult shovelnose. If its caught and turned into caviar, that’s one less pallid to grow to adulthood and breed more sturgeon.

Biologists release Pallid Sturgeon

Biologists release Pallid Sturgeon

Sturgeons spend most of their lives in fast-moving, muddy rivers. But they breed in quiet side channels near sand or gravel bars.

Duck Island Side Channel at the Confluence of the Missouri and Mississippi Rivers

Duck Island Side Channel at the Confluence of the Missouri and Mississippi Rivers

In its attempt to maintain a viable nine-foot navigation channel and to keep the Mississippi and Missouri Rivers from adopting side channels as the navigation channel, the Corps built closing dams across the head of side channels. The closed channels silted in. The pallid sturgeon lost breeding places.

Confluence, Columbia Bottoms, Long Dike on right

Confluence, Columbia Bottoms, Long Dike on right

At the Confluence of the Missouri and Mississippi, a long dike directs the Missouri current into the Mississippi to the right of the dike.

Long Dike at the Confluence

Long Dike at the Confluence

The Corps of Engineers on the Missouri and Mississippi have been working to restore side channels to the rivers. The Corps began cutting notches in dikes to allow water to flow through side channels, keeping them open for sturgeon and other fish looking for a quiet place. The anglers follow.

Notched Dike at the Confluence

For those who are interested in exploring Columbia Bottoms and other sites along the Mississippi near St. Louis, go to TwoTankTours.com and download the Riverlands tour, which covers Columbia Bottoms, Riverlands, the Chain of Rocks, Horseshoe Lake State Park, and Dresser Island. The cost is $7.

Casino at Columbia Bottoms at the Confluence of the Mississippi and Missouri

1890 Map of the Confluence of the Mississippi and Missouri Rivers

1890 Map of the Confluence of the Mississippi and Missouri Rivers

In 1890 the Confluence of the Mississippi and Missouri Rivers was a maze of islands and sloughs, many of which have become attached to the mainland.

The Confluence with Mobile Island in the distance

On Monday the St. Louis County Planning Commission approved, unanimously, the rezoning of a 377-acre site in Spanish Lake, Missouri near the end of the I-270 bridge over the Mississippi.  This the first step in a long list of hoops  the construction of a casino and entertainment complex on site will have to jump through. I figure the complex will go near the top of Wilson Island Bend on the map.

It will be huge and  include a casino, convention center, a theater, hotel, sports bar, buffet, stores, and 18-hole golf course, a wind farm, and paving for 8,000 parking spaces and will be adjacent to the Columbia Bottoms Conservation Area. The developer is Pinnacle Entertainment of Las Vegas, which also owns a complex at Lemay south of St. Louis.

Columbia Bottoms has a long history.

French traders from New Orleans, Pierre Laclede and August Chouteau, establish St. Louis in 1764 ten miles south of the confluence of the Mississippi and Missouri Rivers shortly after the French handed Louisiana over to the Spanish. Four years later Spanish troops built a fort in the uplands, overlooking the confluence. The area became known as Spanish Pond. Today, both the uplands and Columbia Bottoms lie in the suburb of Spanish Lake.

Jacques Marcellin Ceran de Hault de Lassus de St. Vrain immigrated to America in 1794, settled at Spanish Pond, and purchased large tracks of land on the bottoms. He died in 1818, but even in 1868, fifty years after his death, Pitzman’s plat map of St. Louis County shows J. de St. Vrain owning much of the land on Columbia Bottoms, the floodplain at the confluence of the Missouri and Mississippi Rivers.

In the years before the Missouri Department of Conservation purchased 4,314 acres on the bottoms in 1997, what wetlands existed had been drained and turned over to agriculture. A flood protection levee kept out all by the biggest floods. The biggest flood, the Flood of 1993, overtopped the levee and washed in sand and debris.

The Department of Conservation has begun to restore what were once cornfields into a mosaic of shallow wetlands, bottomland forests, prairie, and croplands, all designed to attract resident and migratory wildlife.

Slough on Columbia Bottoms

Slough on Columbia Bottoms

In 2002 the department began constructing roads, a river access, hiking trails, and a viewing stand at the confluence to attract people to the refuge. The department allows hunting, fishing, and trapping during the proper seasons and with proper permits.

Hiking trails lace the refuge. In some cases, hikers have to share the trails with bikers. However, the best, those along the Missouri River are for hikers only. Then there is the unofficial trail to the right of the paved trail as you approach the viewing platform. It goes along the Mississippi, far enough to see the tip of Duck Island, where Bald Eagles nest. Have a look: you will find the nest in the tree at the very tip of the island.

The Unofficial Trail along the Mississippi

For more information on Columbia Bottoms and the riverlands near St. Louis, go to TwoTankTours.com and download the Riverlands tour, which includes information on Horseshoe Lake State Park, Riverlands, Dresser Island and other places. The cost is $7.

An 8,000 car parking lot next to a wildlife refuge? A wind farm next to a wildlife refuge? Do birds and wind mix? Airplanes and birds don’t mix, so how do birds and windmills mix? A casino next to the Confluence of our two great rivers? What if we have a repeat of 1993? It’s possible. Of course it will all be behind tall levees, so why have it on the river at all?

Wind farm near Leroy, Illinois.

Wind farm near Leroy, Illinois.

Not Enough Sediment in Mississippi to Rebuild Louisiana Wetlands

Fragmenting Wetlands in the Barataria Basin at Port Sulphur, Louisiana

Fragmenting Wetlands in the Barataria Basin at Port Sulphur, Louisiana

The dream that we can make enough freshwater diversions from the Mississippi into the Barataria Basin to the west and Breton Sound to the east to reverse land loss is a fantasy.

A pair of geologists at Louisiana State University issued a report last week, noting that we have deprived the Mississippi River of the sediment necessary to counter the raise in sea level and rebuild the Louisiana coast.

The researchers have concluded that the 8,000 dams we have built in the Mississippi Basin are the culprits. Any sediment that may flow out of the uplands into the tributaries gets trapped behind the dams.

Lock and Dam 26, Alton, Illinois

Lock and Dam 26, Alton, Illinois

We built the 26 dams on the Upper Mississippi to turn it into a profitable navigation channel. All the sediment that comes out of the uplands is trapped behind the dams.  The Corps of Engineers must dredge the navigation channel constantly to maintain its 9-foot depth.

There are six on the Missouri, which flows through soft, erodible sedimentary rocks and supplied the Mississippi with 60% of its sediment before the construction of its dams in the 1950s.

Niobrara River, at Niobrara, Nebraska

Niobrara River, at Niobrara, Nebraska

Take the Niobrara River, which flows to the Missouri at Niobrara, Nebraska.  It heads neat Lusk, Wyoming and flows along the northern margin of the soft, erodible Sand Hills in Nebraska, turns north, and empties into the Missouri.

It is a river that somehow has not been dammed or channelized, but it has still been changed by the construction of the Gavins Point Dam downstream from its confluence with the Missouri. The dam turned the Missouri into a lake and raised the level of the Missouri 2.9 meters at the mouth of the Niobrara.

Note: When a fast moving stream meets a still body of water, it deposits its sediment in the still body of water and forms a delta. That’s what the Niobrara does with the sediment eroded from the Sand Hills when it meets the lake-like Missouri. This is the case with other tributaries of the Missouri. It is all retained behind the Missouri River dams.

Missouri River at Niobrara, Nebraska

Missouri River at Niobrara, Nebraska

Before the construction of the dam, the Missouri carried away all that sediment to the Mississippi, which delivered it to a still body of water: the Gulf of Mexico and built the Louisiana coast.

Now what sediment the Mississippi does carry to the Louisiana Coast does not get to it because we have built levees clear to Venice, Louisiana to prevent the river from flooding and depositing its sediment on the coast. Hence, we have to design freshwater diversions to deliver sediment to the wetlands, which are starving for lack of freshwater and sediment. But, now we are finding those won’t work.[1]


[1] Etheridge, F.G., Skelly, R.L., Bristow, C.S., “Avulsion and Crevassing in the sandy, braided Niobrara River complex response to base-belel rise and aggradation,”  In Fluvial Sedimentology by Norman Dwight Smith and John Rogers, found in Google Books http://books.google.com/books?id=7i_pWcmzRZ4C&pg=PA181&lpg=PA181&dq=Niobrara+Missouri+River&source=bl&ots=94teq3rvPZ&sig=_Ua9y4paapkbENbXSDPBU6r6rhQ&hl=en&ei=pS5KSoq_K4f-NZ-c-fIN&sa=X&oi=book_result&ct=result&resnum=6.