It took the U.S. Army Corps of Engineers nearly a hundred years to channelize the Lower Missouri River between Sioux City, Iowa, and the river’s mouth near St. Louis. The reason it took so long for the Army to channelize the lower river had to do with the fact that the Missouri kept destroying the Army’s channelization structures.
In the 1930’s, the Army completed a six-foot-deep navigation channel along much of the river south of Sioux City. But in the 1940’s, a series of massive floods, which originated in the Rocky Mountains and northern plains, washed away over a hundred million dollars worth of pile dikes and revetments. Entire sections of the navigation channel south of Sioux City reverted to a wild state, especially along the reach through western Iowa.
Unwilling to simply abandon the river to the whims of nature, and determined to channelize its lower reaches come hell or high water, the Army engineers returned to the Lower Missouri in the middle 1950’s. By employing new channelization techniques, and aided by the presence of upstream dams, the Army finally checked the Lower Missouri’s ability to meander across its floodplain. Once farmers recognized that the Army had halted the Missouri’s wandering ways, they converted the floodplain’s wetlands, sand flats, oxbow lakes, cottonwood forests, and grassy meadows into corn and soybean fields.
By the late 1970’s and 1980’s, the largest, continuous stretch of fish and wildlife habitat in the Midwest had been transformed into cropland, industrial sites, roadways, and suburbs. Today, a traveler on I-29 through western Iowa or Highway 75 in eastern Nebraska is hard-pressed to actually see the river’s old floodplain because it has been so thoroughly subsumed by human constructs. Nevertheless, a person can occasionally still catch a glimpse of the former floodplain in the gentle undulations that ripple across a bottomland cornfield or in the rainwater that infrequently pools in a long-forgotten oxbow lake.
Lower valley farmers, the Army Corps of Engineers, and the Midwest’s business community considered the remade Missouri an improvement over the wild, meandering river. For these groups, the new Missouri represented progress, while the unchannelized river symbolized waste, inefficiency, and unpredictability. But not everyone agreed with this interpretation of the Army’s handiwork along the Lower Missouri.
By the late 1960’s and early 1970s, duck hunters, commercial fishers, recreational fishers, outdoor enthusiasts, biologists, and ecologists recognized that the Army’s channelization of the Lower Missouri had contributed to an environmental catastrophe the likes of which hadn’t been seen in the Midwest since the era of European-American agricultural settlement. In the 1970’s, the Iowa Geological Survey (IGS) studied the environmental effects of the Missouri River Bank Stabilization and Navigation Project on a segment of the Lower Missouri. In 1979, the IGS published the results of its survey in a booklet titled, “Changes in the Channel Area of the Missouri River in Iowa, 1879-1976.”
According to the IGS, between 1890 and 1976 (which is the timeline that coincides with the construction of the navigation channel), the length of the Missouri from Sioux City to the Missouri state line decreased by 32.2 miles. Although the river naturally straightened and shortened itself during the late nineteenth century and first half of the twentieth century, the Army’s channelization work was largely responsible for the dramatic shortening of the river. From 1890 to 1976, the total acreage encompassed by islands in the river in western Iowa and eastern Nebraska dipped from 5,811 acres to zero, while sandbar habitat decreased from 29,461 acres to 57 acres. The portion of the river floodplain actually covered in water, referred to as the “water area,” fell from 36,617 acres in 1890 to 15,420 acres in 1976. At the same time the river and its floodplain suffered significant habitat losses, the nearby valley lowlands did as well.
In the early 1890’s, the Missouri River Commission surveyed the Missouri and its adjacent lands from the river’s mouth to Three Forks, Montana. The commission published the results of its survey in a series of detailed maps. At the top of this article is one of those maps, depicting a segment of the Missouri River through Monona County, Iowa. If you look closely at the map, you get a sense of the incredible diversity of habitats that once existed along the Missouri in western Iowa and eastern Nebraska. And if you look long enough, you’ll see what we lost when the Army channelized the Missouri.