The Missouri and Ohio Rivers and numerous other smaller rivers drain into the Mississippi River. Altogether the Mississippi drains about 41 percent of the U.S. and some of Canada. In addition to being a drainage system the Missouri-Ohio-Mississippi (MOM) River system can serve as an inland water transportation without equal in the world. However for MOM to function efficiently as such a water transportation system its meanders, silting and flooding must be dealt with. The Army Corps of Engineers was given the responsibility to enhance its capacity for transportation and to control its flooding. The Corps defined its goals as to straighten, channelize, regularize and shackle the Mississippi. In addition the Mississippi required some locks built on its upper reaches to help cargo ships traverse its course.

To control flooding the Corps confined the Mississippi between levees separated by a distance of one mile. This is a narrower channel that existed for the river in its natural state. The sides of the levees were paved to prevent the river from eroding the shore. The Corps also dredged channels for shipping.

In some places the Corps provided for floodways to carry away excess water during flood times. These floodways represented a choice between bad and worst. The floodways took away the possibility of agriculture on some land to give security from flooding on other perhaps more valuable land. In 1927 when a flood threatened New Orleans the Louisiana state government dynamited the levee upstream from New Orleans to save New Orleans from flooding. This of course flooded the rural area of Saint Bernard Parish that might not have otherwise been at risk of flooding.

In 1831 Henry Shreve, for whom Shreveport, Louisiana was named, organized an effort to cut a channel for the Mississippi that would eliminate a meander. Later in 1839 an ancient log jam on the Atchafalaya River was cleared to allow river boat traffic on the upper Atchafalaya. To people surprise the Mississippi started creating an alternate channel to the Gulf by way of the Atchafalaya. This grew over time until by the 1950's thirty percent of the Mississippi's flow was going down the Atchafalaya. In 1953 the Corps of Engineers feared that the Mississippi would all go down the Atchafalaya leaving the Baton Rouge-New Orleans corridor without a river. The Corps petitioned Congress for an appropriation to build a structure to prevent the Mississippi from changing course. However by this time there was considerable development along the Atchafalaya so it was politically possible to take away any of the Mississippi flow that had been going down the Atchafalaya. Therefore the task for the Corps was to build a structure which would stablize and maintain the 30%-70% division of the Mississippi between the Atchafalaya and the main stem of the old channel. For more on this topic see Old River Control Structure.

The lower Mississippi, particularly between Baton Rouge and New Orlean, serves as a disposal channel for chemical wastes. There are 96 chemical plants along the corridor from Baton Rouge to New Orleans that discharge chemicals into the river. This is the legal pollution of the river, but therer is also the illegal pollution and the accidental pollution from the ships carrying cargoes of chemicals. For example, in 1981 the Georgia-Pacific Corporation was responsible for spilling 21 tons of phenol into the river. Phenol is a dangerous chemical that resulted in the water in New Orleans, which depends upon the river for drinking water, having a taste and smell of phenol. New Orleans is concerned about water quality because the incidence of cancer is higher in New Orleans than the rest of the country.

New Orleans has been the largest port of the United States in terms of the value of the goods going in and out. Morgan City is a boomtown based upon the offshore petroleum wells. Morgan City is located on the Atchafalaya River only 23 miles from the open water of the Gulf of Mexico, in contrast to the 95 miles that separates New Orleans from the Gulf.

Southern Louisana is the delta built over the last five thousand years from the silt carried by the Mississippi River. The projects carried out by the Corps of Engineers are depriving the coast line of that silt. As a consequence the offshore barrier islands are being destroyed.

The Corps carried out programs which dried up most of the bayous (swamps) where the Acadians (Cajuns) live. This drastically changed their way of life.

The Corps has left a section of swamp along the Atchafalaya River to serve as a floodway in times of need. This water overflow swamp section is 130 miles long by 35 miles wide. But the Corps has created other projects that put the swamp at risk. In 1965 the Corps created the Mississippi River Gulf Outlet (MRGO) as a short cut route to the Gulf that could be used in times of heavy traffic on the main stem river. The MRGO has led to salt water intrusion in the wetlands of St. Bernard Parish. This intrusion is leading to a salt water desert. Local authorities are trying to halt this desertification by syphoning fresh water from the river upstream. It is difficult to cope with the problem.

The MRGO is little used. Only 3 percent of the cargo traversing the lower Mississippi takes this route. It amounts to only about one ship per day. Nevertheless the Corps sometimes spends over $10 million a year dredging the channel.