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Modeling Flood Control Waterways

Flooding at the McKee Applegate River Bridge in Oregon
McKee Applegate River Bridge in Oregon

Meshing using FLOW-3D's multi-block model
Model area as meshed

FLOW-3D simulation results of flow around piers
FLOW-3D results, water
is colored by velocity

The installation of a new bridge over the Applegate River in Oregon presented some very challenging modeling circumstances for ASCG Inc., a FLOW-3D customer in Colorado. With three drops and an irrigation diversion upstream of an existing bridge (see photo, upper right), the project involved some complicated flow patterns. To resolve the complex domain and minimize the number of computational cells, ASCG made extensive use of FLOW-3D's multi-block model (see figure at center right).

The three step dam diverts water into an irrigation canal. At flood stage, some of that flow overtops the ditch bank and spills onto the far piers. The combination of the complex flow down the dam, water overtopping a large rock outcrop, and the spill from the irrigation canal creates a dangerous situation at flood stage.

Simulations with FLOW-3D yielded an average water surface profile in good agreement with the conventional 2D analytical tool used by hydraulics engineers, but the stepped diversion dam and 6 foot waves could not be handled by a 2D modeling tool. For example, the FLOW-3D simulation showed very unusual spiral flow patterns hitting the far piers.

Using their results from these simulations, ASCG engineers were well-armed to develop designs which stand a better chance of preventing life-threatening situations during flood events.