How Long is the River Really?
When beginning a long journey down the Mississippi River, paddlers are greeted by an iconic sign. It reads:
Here 1475 ft above the ocean the Mighty Mississippi begins to flow on its winding way 2552 miles to the Gulf of Mexico.
The problem with this sign: it’s incorrect.
The Mississippi River is not 2,552 miles long, and it hasn’t been since the 1930s.
The modern Mississippi River is over 200 miles shorter than what the sign indicates!
Let’s rewind to see how we got here.
The earliest attempt to measure the length of the Mississippi River was made by Jacob Brower, an early surveyor in the region, who claimed 2546.52 miles as the total distance from Lake Itasca to the Gulf of Mexico.
Indeed, this was reflected in early versions of the sign at Lake Itasca in 1933.
By 1941, the Mississippi Headwaters had undergone a restoration in partnership with the National Park Service, and the distance increased by 6 miles. How did the mileage change from 2,546 to 2,552 in those eight intervening years? The answer is unclear, but it may simply be they added the distance of Lake Itasca itself, since a raindrop falling at the ‘upstream’ end of Lake Itasca would travel the 6 miles to where the Mississippi River flows out, adding to its total travel.
It is at this point in time that the iconic tree trunk made its debut—a design that still stands at Lake Itasca to this day.
O.K. So the Mississippi River was once around 2,552 miles long. Why is it so much shorter now?
There is much to say about the 1927 flood of the Mississippi River. The short version is that it was the most devastating river flood in the history of the United States.
In the spring of 1927, prodigious and unrelenting rains across the Midwest caused the Mississippi River to rise uncontrollably. The Mississippi River burst out of its levees at multiple points, including at the Mounds Landing Crevasse, flooding an area of ~27,000 square miles. That’s approximately 0.7% of the United States’ surface area—larger than the state of West Virginia. That area was under 6-12 feet of water, which is quite jarring to think about.
It also left 750,000 people displaced and without safe drinking water. Many camps of stranded people were left on levees, the highest point in a vast floodplain. At some places, the Mississippi River reached 50 miles wide, with only the levees and building tops sticking out of the muddy haze.
The 1927 flood was caused in large part by the US. Army Corps of Engineers’ (USACE) policy up at the time: the levees-only policy. This meant that levees were the only flood-control measure in use—the only tool in the toolkit. Other systems were proposed, notably by engineer James Eads, calling for outlet flows. These would allow water to escape into designated unpopulated areas, acting as a pressure release valve of sorts. The USACE was staunchly opposed to this system in 1927, and the Mississippi did not have any outlet channels.
A levees-only policy meant that water in the Mississippi could not leave, except by flowing all the way down to the Gulf of Mexico. In the meantime, it would wreak havoc on the levees as it made its way downstream. In 1927, as colossal amounts of water churned and frothed by each second—shaking, vibrating, and menacing the levees for months—the only course of action was to add more and more sandbags and earth to the levees, hoping the the waters would subside.
The Flood of 1927 was a line in the sand. The devastation heralded many calls for action. This flood was unacceptable, and many looked to the Federal Government to step in to make sure this never happened again.
Put quite simply, there is Mississippi River policy before the 1927 flood, and after the 1927 flood. The two look nothing alike. After such a seismic event, things couldn’t stay the same.
The Flood Control Act of 1928 was one attempt to modernize the Mississippi River Infrastructure and prevent future disasters.
This law directed the USACE and the Mississippi River Commission to investigate possible solutions and create a more flood-proof Mississippi River.
Some of the major actions were as follows:
The U.S. Army Corps of Engineers (USACE) abandoned its long-held belief of a “levees-only” policy. They began to adopt spillways and other “pressure relief” mechanisms. The Bonnet Carre Spillway that protects New Orleans is one of them.
The levees were nationalized, meaning the federal government would begin to manage the levees along the entire Mississippi River. This was to ensure parity and uniformity among states.
The USACE moved the levees back. In this way, it takes a lot more water to rise those last few feet to get above the levee. It lets the water spread out and slow down near the levees as well, to reduce erosion on them.
The USACE made a series of “cutoffs” on the Lower Mississippi River below Memphis.
Digging into that last bullet point brings us back to our original inquiry: why does that sign at Lake Itasca say 2,552 miles? Well, the answer is that until 1927, the river was indeed approximately that long.
In the 1930s and 40s, the USACE made a series of cutoffs, to reduce the length of the river. Why would reducing the length of the river be helpful? In a nutshell, it helps water get to the ocean faster, thereby easing pressure on the levees sooner. Water slows down as it goes around curves, and the more meandering the curve, the more the water slows. With more cutoffs, the water can more quickly make its way downriver, leaving room for upstream water to fill its place without building up.
A couple of key spots were identified for cutoffs, which shaved off over 150-200 miles of river length. The Greenville Bends alone cut off around 50 miles, and the resulting straightaway, Tarpley’s Cutoff, has caused the USACE engineers headaches ever since. But that’s a conversation for another time.
Nowadays, the Mississippi River runs for about 2,340 miles from Lake Itasca to the Head of the Passes. Even this number is not set in stone, and does fluctuate minorly from year to year.
The Lower Mississippi is largely locked in place within the walls of levees, but even within the levees there are multiple paths to take, along either side of islands, for example.
Meanwhile, the Uppermost Mississippi, above Minneapolis, has sections unobstructed by levees, and is still engaged in that age old process of digging new paths downstream.
I’ve been thinking a lot about the Mississippi River since my canoe trip, and some of these are weaving their way into words. Like the true length of the Mississippi, there are many other Mississippi misconceptions and misunderstandings out there.
For example, does it really take a raindrop 90 days to make it from Lake Itasca to the Gulf? Is this old adage really that simple?
I hope to explore this and other topics in the weeks and months to come!
Cheers,
Jean-Canot
ncG1vNJzZmibkaO8pr7AppmlnaJjwLau0q2YnKNemLyue89opKKro57AtLXPqaBmpZmosLC6wp6nraGfo8ButM6wZKWnnpw%3D