"The 2011 Missouri River Flood: Pin-Pointing Trouble Spots"

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

Portions of the city of Omaha, including downtown, sit behind a levee. With a forecast of rain and the high river levels, city engineers needed to know quickly where and how much water was likely to pond behind the levee in order to coordinate their response and prevent serious flooding in the city, and avoid disruptions to downtown businesses, and disruption to economically important events such as the College World Series which was occurring at the time. Fortunately the city already had a detailed hydraulic model of their combined sewer system. 2D overland surface elements were added to the model to evaluate what would happen once flows exceeded the storage in the system. This allowed the model to simulate the flow of water once it left the sewer system and flowed overland down roads, between buildings and across open spaces to where it collected behind the levee. Numerous scenarios were modeled to help city engineers determine where and how many pumps to place to respond to actual and potential flooding. Pump locations and rates were modified in response to conditions as placed and moved about the system as sewer bulkheads and gates were opened and closed in response to conditions in the system. This presentation demonstrates how the city of Omaha staff were able to use a forecast rainfall and a 2-D hydraulic model to aid in emergency planning and placement of pumps to control flooding behind the Missouri River levees during the 2011 Flood.