The Mississippi meander

By Samantha Weinberg

On December 1st 1944, as Allied troops were mustering their forces for the last push across occupied Europe, Harold N. Fisk walked into the Mississippi River Commission (MRC) offices to deliver the fruits of three years of endeavour. A geology professor from Oregon, brilliant and irascible, Fisk had spent his war battling to complete the "Geological Investigation of the Alluvial Valley of the Lower Mississippi River".

By any criterion it is a triumph, an exploration of millions of years of riverine history. But what makes it exceptional are the maps, specifically Plate 22, sheets 1-15. Each is a work of art as well as of scholarship, a minute depiction of a 53-mile (82km) stretch of the river, as measured from north to south.

In Sheet 11, pictured here, the Mississippi winds down the eastern side of its range, its meanders as languid as the southern burr of the citizens who live on its banks. Stretching out across the fertile alluvial plain to the west are the ghost trails—traces of its previous courses, twisting and writhing in a vast intestinal tangle. Each is date-coded by colour: bright green shows its 1880 course, brick red 1820, pale blue 1765, then various striped, spotted and shaded tones which, together, turn the maps into an animated cartoon, layered into a single frame showing how the river has wriggled eastwards over the centuries.

This is physical geography etched large. The Mississippi carries sediment in the faster-moving outer curves and deposits it where the flow is quieter. The bends get tighter and tighter until they join up, whereupon the river takes the shorter route, leaving the amputated curve to close up into an ox-bow lake, like Lake Bruin to the south of this map.

It is also practical geography performed on a large scale. Today Google Maps estimates that the journey by road from Cape Girardeau in Missouri, where the Lower Mississippi starts, to Donaldsonville, Louisiana, where it ends, is 565 miles. This would (in current traffic) take 9 hours, 20 minutes—and that’s with fast cars on an interstate highway. Fisk and his tiny team of four geologists had no such advantages. They took approximately 16,000 soil samples along the river’s routes and, by comparing the results with aerial photographs, pieced together the old courses. Their findings were sent to a W.O. Dement of the MRC to draft as illustrations, drawn, lettered and coloured by hand.

If you were to receive one of the 1,000 printed copies of the report today, it would be tempting to roll the names around your mouth—the Walnut Bayou Segment, the River aux Chenes Subdelta—then tear out and frame the maps and junk the rest. But that would be a mistake: although the Mississippi has run its current course for most of the last century, shored in by man-made levees, it will not be possible to straitjacket the world’s fourth-longest river for ever. And if you were planning, for example, to build a house on the area covered by Plate 22, sheet 15, you would do well to listen to Fisk’s ghost—and stay away from the west bank. ~ Samantha Weinberg

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