Same river, two tales
The IOWA RIVER can be tame and docile. Or it can be a rampaging flood of historic proportions. Anyone that has lived long enough in this county knows full well the extremes of water flow in the river. And we all know how quickly the river is capable of responding to heavy rainfall events when downpours of water cause excessive surface water runoff from the watershed. It happens over and over again. This is an example of natural history at work as Mother Nature continually shapes and reshapes the landscape.
Drought years of little rain are expressed in very low runoff and input to the river from area tributary creeks. For the most part in the Midwest, geologists call it base flow, the slow but steady ‘leakage’ of subsoil moisture downslope toward the river. In this part of the world, our rivers hardly ever go completely dry. Very low river flowage did happen in 1977 and again in 1988. These years stand out because they were exceedingly dry. Flow rates in the river were measured less than 150 cubic feet per second. Wading across the river from bank to bank may have got your ankles wet. Sand bars had been exposed long enough to allow weedy vegetation to grow. At the present time the river flow rate is 181 cfs and decreasing slowly.
The flip side of this coin are wet years and flood events. Topping the record list is a river crest on July 2, 2014 of 22.25 feet and a flow rate of nearly 22,900 cubic feet per second. Many major highways were closed due to water over the traveled surface. Inconvenience was a mild way to describe re-routings people had to use to find other river bridges they could cross. Major floods of the Iowa River near Marshalltown occurred in June 1974, March 1979, June 1990 and June 1991, March, July and August 1993, June 1998, April 2007, April and June 2008, July 2014 and December 2015. There are other instances prior to the 1970s that I do not have data on. Point being that the Iowa River has a reputation that must be respected.
The watershed of the Iowa River begins at Crystal Lake in Hancock County. Approximately 300 miles later, the river enters the Mississippi River. The watershed contains 12,499 square miles of land where surface drainage enters from waterways, small and medium sized creeks or larger streams. The watershed above Marshalltown has 1,532 square miles and we are at river mile post number 222.8 from the Mississippi River. Large and sustained rainfall events north and west of Marshalltown are where all our flood waters will come from. If too much rain falls too fast over already saturated soils, surface runoff grows exponentially. When all this water gathers together, we can expect flooding to some degree.
I have noted periodically in past yeasr of my Outdoors Today stories of one of the historical happenings that has influenced how the river behaves during flood times. Let’s back up to 1912 when some of the landowners in the floodplain lands west of Liscomb, Albion, and Marietta petitioned the Board of Supervisors to ‘do something’ about the erratic moods of the river and its flooding. Lands adjacent to the river were always too wet, poor surface drainage existed, this was not a good situation for conventional tile lines to work. Some were looking for a simple solution to a complex problem. The irony of the matter is that many landowners in the area of drainage district number one (the Iowa River project) were assessed fees to help pay for the dredging. Some could not pay and lost the land they wanted to protected.
It took a few years, but the supervisors relented to the pressure. It is not known if any scientific data was presented to counter the dredging plan, but if there was, it failed. A dredge contractor was secured and heavy equipment was brought in by rail cars to Liscomb, off-loaded and re-assembled on the river to allow digging of a straight channel to proceed. The dredge was basically a floating barge and on its surface was a steam operated scoop shovel. Operators of the shovel simply dug out the soil from in front of the dredge and placed the spoils on one side or the other for disposal. This allowed the barge to float forward a few feet where digging continued. Dredge operations began at the Hardin/Marshall County line in 1918. By 1921 the dredge, named Mary Ann, had dug its way via a new channel to the back side of the Iowa Soldier’s Home (now the Iowa Veterans Home).
The new channel was only about 50 feet wide and was free of all the meandering twists and turns of a ‘normal’ river in a floodplain. From old aerial maps of Marshall County, I was able to determine the most recent natural river course prior to dredging. I measured that length and compared it the new length of the dredged channel. Result: More than 8.2 miles of river course had disappeared! Now the river bed distance was shorter and its elevation changes were steeper. That meant the current could flow faster, at high water flows and especially during flood levels. Faster water carries more silt, sands and clay particles for longer periods of time. Cutting and erosion of land having contact with this fast water was easily degraded and swept away. In turn this lead to a huge degradation of wildlife habitat and elimination of many riparian wetlands.
Just north of the Iowa Veterans Home land where the dredge was tied up at its last point of activity in 1921, the river downstream continued it is natural meandering back and forth pattern. When high flow river stages and periodic flooding took place, all the fast moving water from above Marshalltown met a “roadblock” or should I say “river block” at the Veterans Home vicinity. The tendency for the waters to slow down was inescapable. Flood water had to disperse over the adjacent floodplain. Flooding in and around Marshalltown has increased in its severity in part because of the short-sightedness of actions taken in 1912 and the dredging actions later that decade.
The late John Garwood, my predecessor column writer for the Times-Republican with his signature essays called Sighting Upstream, is the person who related many of the details of the above Mary Ann dredge history lesson. And he told with some delight how a few area outdoor enthusiasts in 1921, who were so disgusted with the incredible damage to the river, its forest and wetlands from this short-sighted happening, took their revenge. As it was told to me, the guard at the docked dredge was engaged in a game of cards and a bit too much beer or other alcoholic beverage was offered to the guard. After he passed out, the dredge mysteriously caught fire. It was destroyed. One thing for sure, dredging could not continue any further. The project was finished.
What was not finished and never will be is what Nature will do in the coming years. We will have dry years, drought years, wetter than normal years and some serious flood events in the future to adapt to. That is what happens because of the incredible weather machine that surrounds earth. It is a system over which mankind is powerless to do anything about. It is our lesson about natural history. Will we learn from it or not?
Garry Brandenburg is a graduate of Iowa State University with BS degree in Fish & Wildlife Biology. He is the retired director of the Marshall County Conservation Board. Contact him at P.O. Box 96, Albion, IA 50005.