"The 2011 Missouri River Flood: A Better Road Ahead - IDOT Designs for Overtopping I-680"

Association of State Floodplain Managers Annual Conference, San Antonio, TX
May 23, 2012
By Anthony Henry

Significant damage was sustained on the Interstate 680 approach roadway embankment to the Missouri River bridges from overtopping due to the flood. The resultant damage prompted the Iowa Department of Transportation (IA-DOT) to evaluate embankment protection protocols. A hydraulic analysis was performed to compute the maximum velocities and overtopping depths associated with a range of conditions possible at I-680 (flow rates, overtopping depths, and upstream (u/s) to downstream (d/s) head differentials) but general enough to be applied to other State of Iowa Highways that have embankments subject to overtopping. From this analysis, a conceptual embankment protection design was developed considering four embankment protection alternatives including vegetated cover, reinforced vegetation, hard armor and reinforced vegetation/hard armor. Details were developed to demonstrate the alternatives as well as to minimize the discontinuity at the pavement shoulder/slope interface.

Currently, this work is now being used to consider ways to incorporate a potential structural embankment protection alternative for the I-680. One proposal currently identified includes construction of a levee downstream from I-680. This flood protection alternative will be analyzed within the context of hydraulic performance (water surface elevations, head differential upstream and downstream of I-680, velocity distribution along the overtopped roadway, bed shear stress), Right-of-Way (ROW) constraints and design efficacy.