The Meandering Mississippi:

A history of a boundary (1820 - 2019)
Detail of the changes in the Mississippi River’s location from 1820–2019.

The process of geomorphology is beautifully captured in a series of maps created by Harold Fisk for the U.S. Army Mississippi River Commission in 1944. Through a rigorous series of samples and surveys, Fisk and his team illustrate the meandering past of the river, from its convergence with the Ohio River, to just north of New Orleans. A quick explanation of river geomorphology (see following image); a river meanders, or becomes more curvilinear, because the radius of the outer bank is less than the inner. This causes the water on the outside to move faster, slowly eroding the bank, and pushing the curve deeper. On the inside, where the water is moving comparatively slower, sediment is deposited, moving this bank further towards the curve. Eventually, as the curve narrows, the water finds a new route, closing off the bend, and forming an oxbow lake.

Quick explanation of river morphology and the development of a meandering river.

In order to analyze this history geospatially in QGIS, I georeferenced all fifteen maps made by Fisk and created shapefiles for the river’s location in 1820, 1880, and 1944 (the current location in 2019 was added from another source). These years were chosen as they represent a relatively short period of time, a period that has infrastructural and geopolitical implications. It also represents the period in which the geopolitical U.S. state boundaries were established.

Overview of river shapefiles extent, detail of specified section. Year refers to location at that time.

You many notice that the Mississippi River’s location in 2019 no longer follows the state boundaries that define sections of Missouri, Kentucky, Arkansas, Tennessee, Louisiana, and Mississippi. But take note these boundaries were established, for the most part, in the early to mid-decades of the 1800s.

Zoomed in examples of the difference between current river location and state boundaries, and the similarities that emerge when viewing historical river locations.

As the river’s location has changed since it was referenced to establish state lines in the early 1800s, the geopolitical boundaries have not. This has left parts of each state on the opposite side of the river from the rest of the state. These areas were calculated by taking the difference of the 2019 river location shapefile and the state shapefiles.

Overview of areas affected by the river location changes.

When we look at each state line in more detail, the area that has “changed” states during the past 200 years is significant. If the state lines were drawn today along the current location of the Mississippi River, hundreds of square miles and thousands of people would become part or resident of a different state.

Darker corresponding shades of state color are areas that are now on opposite side of river from rest of state.

There have been numerous disputes and trials around these state boundaries over the years, however, there has not been conflicts that have initiated violence. This is perhaps due to this particular river boundary not representing an international border; especially between political powers at odds with one another. However, this is not the case with all boundaries that have been established by meandering rivers. While I am not directly suggesting we change our state borders to reflect the Mississippi River’s 2019 location, I do hope to inspire discussions regarding human’s relationship with natural features. How do we adjust geopolitical boundaries when the natural environment is changing? How does this apply to climate change affecting sea level rise, desertification, and scarcity of fresh water? It certainly seems apparent we must plan, politically and in regards to infrastructure, around natural systems rather than against them.

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