Ten thousand years ago, River Warren, a glacial flood, careened down the Mississippi. In the region around Hannibal, Missouri it flowed in multiple channels and 15 wider times than the modern Mississippi. And when River Warren expired, it left behind a sandy terrace, its river bottom. We call the terrace Sny Island, because before it was channelized for agriculture, the Sny River flowed along the valley wall and separated the island from the mainland.
The Sny River was a branching channel of the Mississippi that acts as a yazoo stream, one that flowed parallel to the big river and drained Sny Island. The Sny heads northeast of Hannibal, Missouri and runs south for seventy-three miles between a wide sloping fan–laid down over the sandy terrace by the many creeks that run out of the uplands–and the broad natural levee of the Mississippi. It reenters the river at Mozier Landing. Farmers on the island changed all that at the end of the nineteenth century.
In 1880 they established the Sny Island Drainage district , with the intention of improving the farmland. Beginning in 1883 farmers who lived along the creeks that flow out of the uplands–Hadley Creek, Six Mile Creek, Fall Creek, Bay Creek, Kiser Creek, and McCraney Creek–formed sub-districts within the larger Sny Island Drainage District. They channelized and leveed their streams and delivered them to the Sny and then the Mississippi. Between 1892 and 1907 district engineers shortened the Sny, straightened out its kinks, cleaned out its trees, and dredged excess sediment from it. In 1911 they found it necessary to widen and straighten the Sny.
The completion of the nine-foot navigation channel raised the water level at the mouth of the Sny. Water backed up into the Sny and into the diverted creeks that emptied into the Sny. Silt clogged the channels. Heavy rains that took four days to drain before the dams took four weeks to drain after. Under the Emergency Flood Control Act of 1950, the Corps of Engineers reconfigured the drainage plan for all of Sny Island at a cost of twenty million dollars.
The Corps channeled five creeks that spill onto Sny Island through three diversion channels than ran from the hills to the Mississippi, crossing over the Sny on aquaducts. The engineers built thirteen reservoirs, catch basins for silt streaming out of the uplands, raised and strengthened twenty miles of main stem levee, dredged excess silt from the Sny, and built three pumping stations along its seventy-three mile course to pump out the ditches.
After the Corps finished the drainage system in 1967, farmers on Sny Island complained of seepage in their fields, which they traced to the navigation channel. In 1980 the Corps granted a lump sum payment to the drainage districts which allowed farmers to tile-drain their fields and build private ditches that empty into the Sny via drainage district’s ditches.[i]
[i] Personal communication Edwin Hajic, August 2, 1999; Hajic, Thesis, 206; Gard, William T., The Sny Story, North Richland Hills, Texas: Smithfield Press, 2002, 29, 35, Gard, 41-47, 109-119.