nature & planetThe Public Domain Review1944 · Lower Mississippi River, USA
Harold Fisk's 1944 maps layer centuries of Mississippi River courses into single images
Geologist Harold Fisk, working for the US Army Corps of Engineers, made maps of the lower Mississippi's meander belt, the valley floor across which the river has wandered over millennia. He drew the river's past courses in overlapping colours: a blank current channel for 1944, with older courses from 1880, 1820 and 1765 traced in different colours. Earlier courses came from aerial photographs and geological study. The maps show how deforestation, levees and cut-offs changed the river's path. Floods and sudden shifts known as avulsions can move a river's course in a matter of hours.
Rivers meander because water erodes the outside of bends and deposits sediment on the inside. Over time, a bend can be cut off as the river takes a shortcut, which is an avulsion. Layered over centuries, these changes leave a visible belt of old channels across the valley.
The maps show that the Mississippi is constantly shifting, and that engineering choices shape where it runs and what towns survive beside it. They remain a clear model of how geology and human intervention interact.
The Mississippi has the third largest watershed in the world.
Image: The Public Domain Review
