14 Oct 2020

Red River Structure Physical Model Study

Abstract: A proposed Red River Structure (RRS), intended to function as one of three gated structures comprising the Fargo-Moorhead Metropolitan Area Flood Risk Management Project, was tested in a general physical model. A 1:40 Froude-scale was applied to model the structure, engineered channels, existing bathymetry/topography in the Red River and overbank areas, and the proposed Southern Embankment. The physical model was used to ensure that the RRS could pass at least 104,300 cfs during the Probable Maximum Flood while maintaining a maximum pool water surface elevation of 923.5 ft. The physical model was also utilized to optimize the approach structure, stilling basin, retaining walls, and erosion protection designs. The physical modeling effort resulted in an optimized stilling basin wall, retaining wall, and end sill geometry/configuration where erosive conditions were not observed outside and adjacent to the stilling basin. Properly designed riprap (St. Paul District’s R470 gradation) proved to be successful in protecting the proposed RRS from potential scour downstream. The modified approach wall design proved to be successful in creating safe approach flow conditions as well as acceptable flow separation patterns. It is recommended that Alternative 3 be the design used going forward.

14 Oct 2020

Red River Structure Physical Model Study

Abstract: A proposed Red River Structure (RRS), intended to function as one of three gated structures comprising the Fargo-Moorhead Metropolitan Area Flood Risk Management Project, was tested in a general physical model. A 1:40 Froude-scale was applied to model the structure, engineered channels, existing bathymetry/topography in the Red River and overbank areas, and the proposed Southern Embankment. The physical model was used to ensure that the RRS could pass at least 104,300 cfs during the Probable Maximum Flood while maintaining a maximum pool water surface elevation of 923.5 ft. The physical model was also utilized to optimize the approach structure, stilling basin, retaining walls, and erosion protection designs. The physical modeling effort resulted in an optimized stilling basin wall, retaining wall, and end sill geometry/configuration where erosive conditions were not observed outside and adjacent to the stilling basin. Properly designed riprap (St. Paul District’s R470 gradation) proved to be successful in protecting the proposed RRS from potential scour downstream. The modified approach wall design proved to be successful in creating safe approach flow conditions as well as acceptable flow separation patterns. It is recommended that Alternative 3 be the design used going forward.