Unseen and unnoticed: The underwater post-flood cleanup you may not think about

Mighty Miss gets a post-flood sweep as upstream silt and sedimentation begin to shift.

ROCK ISLAND, Illinois-- Cleaning up after peak flood season is an expensive and frustrating task for city infrastructure, homeowners and local businesses, but even the Mighty Miss has some tidying up to do as the floodwaters recede.

Upstream, silt and sedimentation begins to shift as river water returns to more normal levels. To maintain a 9-foot navigation channel, U.S. Army Corps of Engineers Rock Island District dredged part of the river near Centennial Bridge on Tuesday, June 2.

Samatha Heilig, spokeswoman for the Corps of Engineers, said dredging the river is a continual process that is common practice after flooding.

"We are responsible for maintaining 9-feet for navigation, so they are going in and reestablishing that normal depth," she said in a phone interview.

Heilig said there are survey vessels that first identify areas of need before dredge crews are sent in to address any build up. How often the river is dredged varies year-to-year and flood-season to flood-season.

A floating pipeline discards dredged material from the river at various placement sites depending on need, according to the Corps of Engineers website. Along the shoreline, the material can restore recreational beaches that diminish due to erosion. Upland, the dredged material can be placed at industrial sites or on levees.

Some of the material may be placed in a thalweg, an area deeper in the river channel, where it becomes a part of the riverbed sediment.

The Corps of Engineers offers clean, free dredged material for uses such as shore protection, agriculture or habitat enhancement.

"Dredged material has not been exploited for its full economic, social, and environmental potential because of costs and the prevailing view that dredged material is waste," the Corps of Engineers website says.