Confluence was contracted by an engineering firm to provide analysis of bridge structures following high flooding events in four counties:  Judith Basin County, Blaine County, Petroleum County, and Fergus County.   Bridge replacement designs were submitted to the county officials, along with Confluence’s HEC-RAS modeling.

Confluence determined flood flows for several streams using available USGS gage data, regression equations, and rainfall/runoff methods.  Cross section survey data was entered into a HEC-RAS model, along with hydrology information.  The HEC-RAS models that Confluence water resource engineers developed were used to evaluate any impact to the flood water surface elevations and velocities from the proposed bridge.  Additionally, scour depths were calculated for the proposed bridges.

Confluence water resource engineers routinely team with firms to offer to clients comprehensive services that include not only civil and structural engineering services, but additional stream analysis.

County bridge over the South Fork of McDonald Creek near Grass Range, MT.

Timberline Road Bridge, Fergus County, MT