Formatted Title:

Upper Mississippi River and Dogtooth Bend Peninsula: Hydrodynamic and Sediment Transport Modeling

Background/Objectives:

On January 2, 2016, the Len Small levee on the Upper Mississippi River near Cairo, Illinois, breached. Since then up to 35 percent of flow in the Mississippi River has flowed through the crevasse, 3 miles across the Dogtooth Bend Peninsula, shortening the journey from 17 miles via the main Mississippi River navigation channel. A hydrodynamic and sediment transport model study investigated breach flow conditions and sedimentation to identify potential solutions to prevent cutoff development.

Approach/Activities:

The AdH hydrodynamic model was calibrated to stage in the reach and breach outflows. Soil and geologic maps were investigated to determine soil parameters and the long-term stability of soil formations on the Dogtooth Bend Peninsula. A sediment transport model, using AdH with SEDLIB, was built upon the hydrodynamic model and soil mapping efforts and calibrated to areally-averaged channel bed and floodplain elevation changes for 2015 and 2017 flood events. The model provided a foundation for comparing alternative measures to minimize further erosion of the Dogtooth Bend Peninsula.

Results/Lessons Learned:

Results for the alternative involving reforestation of the floodplain were quite sensitive to the friction scheme utilized. Analyses of friction formulations and model sensitivity were necessary to parameterize friction and properly model flow through the (hypothetically) reforested floodplain. Model results were used to inform alternative designs and to perform a semi-quantitative risk assessment of channel cutoff formation.

Christopher Wallen

Affiliation

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Upper Mississippi River and Dogtooth Bend Peninsula: Hydrodynamic and Sediment Transport Modeling