In October 2017 I went on a float fishing trip with a friend from Missouri down the Eleven Point River in the Ozarks. A record flood occurred in the northern Ozarks in the spring of that year. The Gasconade and the Eleven Point rivers were hit with devastating runoff from a slow-moving thunderstorm system that produced days of rain. The rivers rose over thirty feet above their normal levels.
Narrow valleys with lots of trees and a fairly steep gradient on both of those rivers resulted in tremendous scouring of the river channels. Thousands of large trees were knocked down, creating woody debris dams that knocked down bridges. Many homes were flooded and boat landings disappeared.
By the time we fished the Eleven Point things had settled down, but my friend Frank said that the channel, pools, riffles and gravel bars had changed remarkably from before the big flood.
A similar event occurred here. On Sunday night and Monday, June 28-29, a large thunderstorm system parked itself over western Wisconsin and eastern Minnesota. Over 9 inches of rain fell near Baldwin, Wisconsin. The area between Hammond and Woodville received the most rain, producing flooding on the Willow, Kinnickinnic, Rush and Eau Galle Rivers. A man drowned when his car was washed into a ditch north of Baldwin. Many bridges and culverts were washed out. Highways 63 near Baldwin and Highway 29 in Spring Valley were impassable.
The Kinnickinnic River crested at 21.45 feet at the Clifton Hollow USGS gage, nearly 12 feet above its normal base flow level. The peak river discharge was estimated to be 6,270 cubic feet per second, the highest recorded there. The normal base flow of the Kinnickinnic River at Clifton Hollow is about 110 cubic feet per second. The normally placid impoundments in downtown River Falls were a fast-moving torrent, conveying sediment and trees right on over the dams.
Homes were flooded in Martell and El Paso along the Rush River. Many floodplain trees were knocked over creating woody debris accumulations. The rapidly moving water scoured around and under obstructions, moving sediment, cutting steep banks and scouring the river channel down to limestone cobbles and bedrock.
Moving water is very powerful. Flowing water just over ankle deep can knock you off your feet. If you are driving or walking and come to a flooded road, TURN AROUND, DON’T DROWN. Rivers carve their way and form their own channels. What looks like a shallow flooded roadway may have deep channels through it already.
The late Dr. Luna Leopold, son of Dr. Aldo Leopold, was the first chief hydrologist at the USGS. He set the course for the USGS in understanding river flows, groundwater and surface water interactions and long-term data collection. Today, the USGS is the world’s largest provider of hydrologic information with a mission to collect and report reliable, impartial, and timely information needed to manage the Nation’s water resources.
One of my favorite books is "Fluvial Processes in Geomorphology" by Luna Leopold, John Miller and M. Gordon Wolman. They thoroughly explained how river systems transport water and sediment and shape river channels and floodplains. Leopold wrote, “The river is the carpenter of its own edifice.”
Dan Wilcox writes a periodic column. Send comments and suggestions to him at firstname.lastname@example.org. Please send any comments and suggestions for this column to him at email@example.com.