There were temporary river waterfalls where the Mississippi ran backwards during 1811-12 earthquakes. It happened early on Feb. 7, 1812, when a thrust fault created a sudden dam several feet high in the bottom of the river loop near New Madrid.
The main section involved was from island 10 northward about 10 miles to island 8. It lasted for a few hours, though the new dams/waterfalls lasted for a few DAYS, and ruined several flatboats. For an authoritative source, see the CERI Enigma paper (link below).
red=lift
blue=drop
~30 feet
Feb 7 1812
See above left the Reelfoot fault crosses the Mississippi three times (just above the red "Reelfoot scarp"). The uplift caused both a dam and waterfalls at different locations. [The Reelfoot Scarp is listed in the enigma paper as being raised eight meters (26 feet). Some listings say 10 meters (33 feet).] Many researchers now put the 1811-12 magnitudes in the 7 range instead of 8's, because they use a newer intensity scale.
Also note how the scarp uplift dammed a creek and created Reelfoot lake, just east, on Feb 7, 1812. This pressure came from a southwest-dipping reverse fault (see thrust fault at left). Earlier shakes, further south, had come from the sideways motion of a strike-slip fault (3rd illustration at left).
The damming of the Mississippi River temporarily made the water run backward for a few hours. details | eyewitnesses | illustration
It "created one waterfall or rapids and two flow barriers on the Mississippi River's Kentucky bend; an additional falls may have formed on the bend's western limb [about 7 miles downstream from New Madrid] by deformation in the hanging wall" [Enigma].
The hanging wall upstream of New Madrid created an uplift that obstructed flow near island #10 (in bottom of loop, just above Reelfoot scarp) and a downdrop falls or rapids downstream of the island. It generated the great upstream wave and retrograde current.
Really?
Some sources, including a USGS web page, say the river didn't really run backward, but just seemed to, as it spread out over surrounding land, after Mother Nature dropped dams across it. The most authoritative source is probably the Enigma paper, and eyewitness accounts from it and and others, which mention a "great upstream wave and retrograde current". Ask the boatmen who were rudely awakened in the middle of the night, and had to hold their hats on while their boat went rapidly upstream for "more than a mile," ... "four miles" ... "at the speed of a fast horse" ... "It was a current going backward" (see below).
Like the Falls of the Ohio?
Eyewitness Mathias Speed and perhaps others compared the falls temporarily created between Island 10 (bottom of the loop) and New Madrid with the "Falls (rapids) of the Ohio" which were a river landmark / obstacle adjacent to downtown Louisville, Ky.. A park naturalist described those falls for us:
The "Falls of the Ohio" dropped 26 feet over 2.5 miles as rapids, with lots of small drops.
The largest single drop was about 15 feet in the center of the river where a hydropower plant is now located - alongside Louisville.
Courtesy David Rumsey collection.
Above left: Computer generated image. Dots represent quakes below New Madrid area. See the SLOPE. One side rose as much as 33 feet, damming the river at least two places, and creating waterfalls. Dot image from seismologist Roy Van Arsdale through History Channel.
This is an oversimplified diagram of the shifting during the third main (Feb 7, 1812 3:45 am) quake. Some eyewitnesses mention six to 12 foot or more vertical walls in the river for a short time before the current wore them away.
One said the reverse current pushed his boat backward four miles. Another said it was at the speed of a fast horse, and he had to hold onto his hat to keep it on. Another reported a large hole in mid-river, with water pouring into it.
See the riverbank trees in this 1938 New Madrid Ferry photo. Imagine a similar scene in 1812, pre-dawn, with trees continually falling into the river, as current runs backward and finds new places to go. Underground horrible "thunder" ... a form of lightning ... air filled with coal dust.
The Ohio River ice had broken loose, and several boats headed south had just made it to the New Madrid area the day before, which was Feb. 6th. Some boats (that went sailing rapidly backwards at 3:45 a.m.) were anchored at Island #9, halfway up the right section of river loops. Two flatboats survived being swept over falls (midsection of river loops) just downstream of Island #10 . A typical uplift in this area is as much as 10 meters (32 feet).
The next intersection of Reelfoot fault with the river was immediately downstream of the town New Madrid (within 1 km). It uplifted the riverbed by one-to-several meters [Enigma].
Large aluminum and power plants are east of Marston, very close to the 5 in top center map that denotes the largest of the 1811-12 quakes, and possibly the largest quake ever recorded in North America.
"On the evening of Nov. 15 (?), we tied up eight miles north of New Madrid near the house of my cousin... (eight miles upstream of New Madrid would have been three miles downstream from Island #10.)
"In a moment, so great a wave come up the river that I never seen one like it at sea. It carried us back north, up-stream, for more than a mile. The water spread out upon the banks -- covering three or four miles inland.
"It was the current going backward. Then this wave stopped, and slowly the river went right again.
"Everywhere there was noise like thunder. The ground was shaking the trees down. The air was thick with something like smoke. There was much lightning.
--Firmin La Roche, a French fur trader of St. Louis was taking three boats of furs to New Orleans. He scribbled this note in New Orleans Feb. 20, saying it happened in November, but the description and location seem to fit quakes in which the other boatmen reported sailing backward.
Island #10 (bottom of loop) was later famous for a Civil War battle. pic | map | more. Read how the union ironclads sneaked past rebel troops during the night, to help open the river. The battle there came a week later.
This map shows 1811-12 uplift, subsidence and submergence. Search for dip-slip and strike-slip animations.
Google Earth map above shows approximate area of uplift of "Tiptonville Dome". New Madrid is at top of river loop. Reelfoot Lake is at lower right. The uplift continues to the north as "Sikeston Ridge" see diagram.
Above is from a postcard.
In Mark Twain's book Life on the Mississippi, he reports on the six-decade long feud between the Darnell and Watson families and other elements of life in the Bend. "In no part of the South has the vendetta flourished more briskly, or held out longer between warring families, than in this particular region,” he wrote. Twain continues:
From stone for the Madrid Bend Familes' Cemetery (known in official registries as Whitson Cemetery (google map)). Both families belonged to the same church ... They lived each side of the line, and the church was at a landing called Compromise. Half the church and half the aisle was in Kentucky, the other half in Tennessee. Sundays you'd see the families drive up, all in their Sunday clothes, men, women, and children, and file up the aisle, and set down, quiet and orderly, one lot on the Tennessee side of the church and the other on the Kentucky side; and the men and boys would lean their guns up against the wall, handy, and then all hands would join in with the prayer and praise; though they say the man next the aisle didn't kneel down, along with the rest of the family; kind of stood guard. --from Wikipedia "Kentucky bend"
Also note how the scarp uplift dammed a creek and created Reelfoot lake, just east, on Feb 7, 1812. This pressure came from a southwest-dipping 
