Hydraulics/Scour Analysis for Bridges in Regional Park

Client: San Francisco Public Utilities Commission
The San Francisco Public Utilities Commission (SFPUC) is planning to build up to three bridges across upper Alameda Creek, in the Sunol Wilderness Area. The bridges provide important access to critical water supply facilities.

WRE conducted hydrologic and hydraulic analyses to support recommendations for bridge deck placement, bridge design, and scour protection of the channel bed and streambanks.

WRE performed a hydrologic analysis to determine the design flow rate (i.e., the streamflow that would safely pass under bridge structures) for the proposed crossings. A 100-year, 24-hour storm was selected as the design storm.

WRE engineers then analyzed stream hydraulics to determine creek water levels and flow velocities during the design storm event. They performed a sensitivity analysis to assess the effect of different bridge parameters on water levels and energy losses.

WRE examined the potential undermining of bridge structures by storm flows and identified the level of armoring necessary to prevent excessive scour around creek crossings.