Meander Maps Illustrate the Mississippi River's Dynamic Geological History

Throughout its history, the Mississippi River's floods and currents have loosed it from its banks, changed its shape, and moved its borders. A glimpse of the Mississippi on any map reveals its dramatic meanders, alterations in shape that occur over time, formed by the river's own dramatic movement. A series of hand-drawn maps from the 1940s trace those meanders' changing courses through the centuries.

Encyclopaedia Britannica defines the meander, a component of a river system, as an "extreme U-bend in the course of a stream, usually occurring in a series." Meanders are a phenomenon of elevation and erosion. They form when the velocity of the water moving downstream erodes one bank and deposits alluvial materials—sand, rocks, and sediment—on the other. Along the way, the deposits build up, creating curves and bends in the fluvial channels. As described by Encyclopaedia Britannica, the winding Mississippi is "a classic example of a meandering alluvial river; that is, the channel loops and curls extravagantly along its floodplain, leaving behind meander scars, cutoffs, oxbow lakes, and swampy backwaters."

Dr. Harold N. Fisk, a consulting cartographer and geologist for the Mississippi River Commission of the U.S. Army Corps of Engineers, is responsible for a series of maps charting the Mississippi's changing appearance. Fisk, at the time a professor of geology at LSU, studied the river's diversions in order to complete his 1944 report, "Geological Investigation of the Alluvial Valley of the Lower Mississippi River." The report explores the flow of the river and the activity of its floodplain over millennia. It's accompanied by maps and diagrams, including 15 vibrant, hand-drawn meander maps that comprise Plate 22 and depict, as described on each sheet, varying "Ancient Courses" along the "Mississippi River Meander Belt."

The maps depict portions of the Mississippi River at locations stretching as far north as Cape Girardeau, Missouri, and as far south as Donaldsonville, Louisiana. The data is collected from 16,000 borings, which provide details about the soil and sediment of the area surrounding the river. According to the report, "a few of these borings were drilled to depths of more than 13,000 ft., many of them to more than 10,000 ft., and most of them reached below a depth of 5,000 ft."

The U.S. Army Corps of Engineers commissioned Fisk's report while their work on the Mississippi was underway. Throughout the 1930s and 1940s, following a devastating 1927 flood, the organization attempted to manage the river and mitigate flooding with levees, dams, and dredging. Spillways and diversions were intended to contain and direct the river, however many have argued that this work has actually increased the likelihood of flooding, particularly along the lower Mississippi.

In a 1987 essay, Toni Morrison describes the human intervention in the life of the river and draws a connection between the fluctuating waters and the project of memory: "You know, they straightened out the Mississippi River in places, to make room for houses and livable acreage. Occasionally the river floods these places. 'Floods' is the word they use, but in fact it is not flooding; it is remembering. Remembering where it used to be. All water has a perfect memory and is forever trying to get back to where it was." She connects the movement of the river to the act of writing, saying, "Writers are like that: remembering where we were, what valley we ran through, what the banks were like, the light that was there and the route back to our original place. It is emotional memory—what the nerves and the skin remember as well as how it appeared."

Fisk's maps bring those "memories" of the courses the river once ran—that geologic history—to life in curves and colors. The series is easily identified by the distinctive use of color, which corresponds to years recorded in the maps' keys and shows the results of the investigation's extensive research. This, in turn, helps to illustrate a dynamic landscape embedded with the memories of its changes. Examining the river's history, particularly as the effects of climate change make unprecedented flooding commonplace, also provides a reminder that no borders are immovable. Even the Mississippi will continue to change its shape.

Prints of the sheets are available for purchase from online print shop 20x200, who describe what results when you see Fisk's research—and a portion of the Mississippi's geological record—illustrated in the historic maps: "Fisk drew more than geographic data, he also found the river's heart in this jumble of loops and purls. The river finds its personality reflected in this explosive, autumn-colored palette, its constantly churning rhythm shaping the soil, digging out a constantly changing place so distinctively its own. From prehistory to the 20th century, these maps are made for the ages."

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What historic maps bring the landscape to life for you? Have you ever seen the Mississippi's meandering channels in person?