Deep time and deep water on the Illinois River

By Gregory Vogel


             Attempts at flood control are nothing new along the Illinois River, and the U.S. Army Corps of Engineers' plan to raise the height of the Nutwood Levee is only the latest in a tradition of human adaptations to rising water stretching back thousands of years.  Located along the southern stretches of the Illinois above St. Louis, the Nutwood Drainage and Levee District surrounds farmland, rural homes, and several miles of Route 100/16 on the east side of the river.


            "One to five miles wide, deeply overflowed in every freshet, filled with bayous, ponds, and swamps, and infested with wild beasts" is how Captain Howard Stansbury described the Illinois in 1838.  Aside from the occasional wild beast, the river itself is a very different creature these days.  Drained, dammed, dredged, cleared and lined with levees, a visitor from 100 years ago would have a hard time recognizing the landscape today.   


            About half of the 400,000 acres of bottomland along the Illinois River are now behind levees, and much of the other half is drained and tilled.  The wetlands are dry, backwater lakes are empty, and most of the floodplain simply doesn't flood anymore – at least on a regular basis.


            Whether these changes are progress in the name of civilization or regress in the name of the environment depends on your point of view, but there is no doubt that they are dramatic, large-scale, and for current purposes irreversible modifications to an entire landscape.  Recent flooding along the Missouri River has once again added a sense of urgency to flood control measures, and once again led to questions about the wisdom of the current levee system. 


            There is opposition to the Corps' plan because levees are inherently selfish constructions, flooding Peter to pay Paul as water backs up and raises river levels somewhere else.  With farmland on the east side of the river, towns without levees on the west, and Route 100/16 connecting both to the world outside of the lower Illinois, the opposition comes from deciding who is Peter and who is Paul when the Nutwood Levee is raised. 


            As explained in a letter to area landowners, the Corps of Engineers evaluated the potential effects of raising the levee by generating a computer model of "an incredibly rare flood event that has never been recorded by man."  Note that "recorded by man", in the Corps' terms, is a time span of about 200 years.


            Archaeologists study humans and the natural environment with a view toward deep time.  This means we look back as far as we can in the archaeological record (deeper in time generally corresponding to deeper levels of archaeological sites), to search for patterns or strategies that make sense.  We also look for those that don't. 


            The valley of the Illinois River formed about 17,000 years ago.  While relatively young geologically, this is still deep enough time for serious perspective.  In taking into account only 200 years of flood records the Corps is missing 16,800 years of data.  What happened in that time?


            A map of archaeological sites along the Illinois shows a pattern typical of most rivers: major settlements are concentrated on high ground near enough for easy access to water but far enough from major flooding.  This has been the case for at least 9,000 years, but there are exceptions to this pattern.  Some archaeological sites in the floodplain are hunting camps or other temporary way stations, almost certainly inhabited only at times of low water.  Others are more substantial.  Prehistoric villages, temple mounds, and other permanent settlements can be found well within the bottoms and close to the river itself. 


            Geological evidence shows a long record of floods during this same time.  Minor floods on an annual or near-annual basis covered the sites with sediment, slowly burying them year-by-year.  Larger floods filled the valley bank-to-bank, scouring pools, changing the course of the river and its tributaries, and greatly altering the overall landscape.  
            Many of the large bottomland sites were occupied before and after major flood events, so the people must have adapted well enough to continue life in the bottoms.  This despite a variety of flood regimes as the river itself adapted to the shifting climate of the last few millennia.  The natural state of nature is dynamic, unlike the levees built to tame it. 


            The natural state of human societies (at least the successful ones) is dynamic as well.  This has been the hallmark of civilization as long as we've been around – failing to adapt to the natural environment has only led to failures of civilization.  How successful we will be in forcing the natural environment to adapt to us is still an open question.


            The Corps of Engineers solicited public comment on the Nutwood Levee project only after, it seems, the decision had already been made.  Let's hope the Corps chose right in deciding between Peter and Paul.  Levee or no, the Illinois River will continue to flood.  Corps of Engineers or no, the floodplain environments will continue to evolve and humans, along with other plants and animals, will adapt.  Or we will not.