Measuring Suspended-Sediment Concentrations, Grain Sizes and Bedload using Acoustic Doppler Velocity Meters and Echologgers in the Lower Chippewa River, Wisconsin

Science Center Objects

Sediment from the Chippewa River deposits in the Mississippi River navigation channel, sometimes disrupting commercial barge traffic and resulting in expensive and ecologically disruptive dredging operations. The USGS is using new applications of hydroacoustic technologies to better understand sediment transport in the Chippewa River and associated effects on commercial navigation.

The Upper Mississippi River (UMR) provides critical habitat for hundreds of aquatic species and also serves as an important economic resource by providing the upper Midwest with a transportation link to the rest of the world. The UMR waterway consists of a stairway system of locks and dams that enables barges and other large river vessels to traverse the river and transport large amounts of bulk goods. The St. Paul District of the U.S. Army Corps of Engineers (USACE) is responsible for lock and dam operation and for navigation channel dredging on the UMR between Minneapolis, Minnesota and Guttenburg, Iowa.

Reliable, consistent measurements of suspended and bedload sediment are important for efficient channel maintenance. Sand-sized material in suspension is of particular interest because of the costs associated with navigation channel dredging and because sand is the dominant sediment size in the UMR.

In 2014, sediment deposition in the navigation channel caused channel closures downstream of the confluence of the Chippewa and Mississippi Rivers, delaying UMR commercial navigation for a period of three weeks. This event was costly to both private industry and the federal government, and several federal and state natural resource agencies raised concerns about effects of emergency dredging on aquatic habitats.

To better understand sediment transport in the lower Chippewa River, the USGS began a study in cooperation with the USACE and Northern Arizona University to deploy hydroacoustic equipment at the USGS streamgage in Durand, Wisconsin (05369500). Two side-looking, single-frequency acoustic Doppler velocity meters of different frequencies are being used to differentiate sediment particle sizes in suspension, and a multibeam echosounder is being used to track changes in the shape of sand dunes along the river bed. 

Continuous hydroacoustic measurements are being compared to physically-collected suspended sediment, bedload, and bed material samples to relate changes in sediment transport to spatial and temporal changes in streamflows. In addition, calculated loads and dune movement rates will be compared against two different multibeam bathymetry-based methods of estimating bed transport. Finally, a modified Einstein procedure will be used to calculate sediment loads for comparison to load estimates from the early 1990s that were calculated using the same methods.

 

This study was made possible through collaboration with the USGS Grand Canyon Monitoring and Research Center.

 

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.