Hydraulics & Waterways

Oral

392558 - Ice Jam, Two-Dimensional, and Levee Breach Modeling at Miles City, Montana

Tuesday, June 5
8:30 AM - 10:00 AM
Location: Regency Room

Miles City sits at the confluence of the Tongue and Yellowstone Rivers in eastern Montana. Both rivers are largely unregulated and experience ice-affected flooding. The community has a non-accredited levee protecting much of the city from both rivers; however, the levee exhibits numerous engineering and maintenance deficiencies including erosion problems, mature trees on the levee, and structural encroachments along the levee toe.
Efforts completed for a U.S. Army Corps of Engineers Section 205 Study include one-dimensional open water and ice jam modeling and two-dimensional levee breach modeling. Difficulties associated with the study include the coincidence of flooding on the two rivers and a high level of uncertainty with respect to ice effects and levee breach parameters. A number of sensitivities were conducted to evaluate the key parameters with respect to flooding in the community. The Hydrologic Engineering Center’s River Analysis System (HEC-RAS) was used for both the one-dimensional and two-dimensional modeling.
While the highest river stages are typically caused by ice-affected flooding, open water floods can also impact the community. Composite stage-frequency curves were developed from the one-dimensional model based on FEMA guidance. These curves, combined with balanced hydrographs, were transformed into stage-hydrographs which were used as boundary conditions for the two-dimensional model.

Curtis J. Miller


U.S. Army Core of Engineers

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392558 - Ice Jam, Two-Dimensional, and Levee Breach Modeling at Miles City, Montana



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