Daily News Podcast
Daily Newsletters
116 3rd St SE
Cedar Rapids, Iowa 52401
Keeping an eye on moving rivers
Wild Side column: It’s not unusual to see shapes shifting on Eastern Iowa rivers
The Wapsipinicon River at Troy Mills flows past an abandoned channel on the left through a recently established channel on the right. Most rivers and streams occasionally change course through the natural process of meandering. (Orlan Love/correspondent)
The concrete boat launching ramp at the Troy Mills Wapsi Access looks a little out of place, terminating as it does in a glorified puddle.
At this Buchanan County park about midway between Quasqueton and Troy Mills, the river into which boats had once launched and landed has moved about a quarter mile to the west, leaving the ramp high if not quite dry.
What once was the river’s briskly flowing navigable main channel is now a bed of sand watered only by a narrow ankle-deep creek.
A concrete boat ramp at the Troy Mills Wapsi Access has been rendered useless after the main channel of the Wapsipinicon River migrated west about a quarter mile. (Orlan Love/correspondent)
Rivers change course more than you might think — a product of their natural tendency to meander.
Rivers turn away from obstacles and seek the path of least resistance, which accounts for the rocky bends favored by anglers on Eastern Iowa rivers.
But even in the absence of obstacles rivers follow winding paths, according to Jerry Dennis, author of “The Bird in the Waterfall: A Natural History of Oceans, Rivers and Lakes.”
Even rivulets of rain running down a windshield turn one way and then the other, Dennis writes.
Subtle forces cause flowing water to depart from a straight course, and centrifugal force amplifies those deviations.
A shallow creek winds Nov. 18 through a deep bed of sand that was once the main channel of the Wapsipinicon River. Through the natural process of meandering, the river gradually cut through a sharp bend, establishing a new channel about a quarter mile west of the old one. (Orlan Love/correspondent)
As the stream begins to bend, current accelerates on the outside increasing erosion and deepening the channel there, while slackening current on the inside deposits sediment that accumulates as a point bar.
The process is a blessing to us wading anglers as it provides us with a comfortable place to stand (the shallower point bar on the inside of the curve) within easy casting distance of the deeper, fish-favored pools along the outside curve.
Over time the bend sharpens, forming a loop through which the river may eventually cut a new channel, often leaving behind an oxbow lake that is cut off from the river except in times of high water.
Mark Twain noted the phenomenon in “Life on the Mississippi,” in which he discussed several historic cutoffs that changed state boundary lines, transferred towns from one state to another and shortened the river’s course.
After documenting several examples of such shortening, Twain used “science” to “prove” that in “742 years … the lower Mississippi will be only a mile and three quarters long.”
Because of the river’s near constant shape shifting, Twain said a “lightning pilot” like himself always had to be updating his river knowledge to keep pace with the changes
The same holds true for paddlers and anglers on the Wapsipinicon and other Eastern Iowa rivers, though the changes we encounter are less sudden and dramatic.
