Darby Creek Bridge
Teton County, Idaho, ID, USA
Teton County Idaho Public Works
Stream stabilization and flood analysis
Services
Hydrologic Analysis
Hydraulic Analysis
Floodplain Mapping
Engineering
About the project
These two projects included replacing an old wooden bridge and road re-construction along County Roads S2000E and replacement undersized culverts on S1000E over Darby Creek, as well as stabilization of the creek banks in the vicinity of the bridge replacement projects.
How we did it
The design team lead by Harmony Design & Engineering included Jorgensen Associates and Biota Research and Consulting. This team worked together seamlessly to provide surveying, hydraulic analysis, hydrologic analysis, morphologic review, structural engineering, and final construction documents for the bridges and associated bank stabilizations. This team also obtained necessary permits and approvals for Teton County, including Floodplain Development Permit, COE/IDWR Stream Alteration Permits, and FEMA CLOMR and LOMR applications.
Hydraulic analysis of the bridges was completed by Harmony and the new bridges allow for conveyance of the 1% annual chance (100-year) flows under the structures and 2-ft of freeboard above the 2% annual chance (50-year) peak flow water surface elevations. The sizing and placement of the bridges took into consideration the geomorphology of the stream, vertical and lateral stability of the creek, as well as stream velocity and shear stresses in the vicinity of the project. Road re-construction design was guided by County design standards for sight distance in order to improve safety.
The crossing at County Road S2000E was constructed in 2014. Construction of the two box culvert crossings at County Road S1000E was completed during the spring of 2017. Both projects demonstrate how county infrastructure can benefit from appropriate fluvial system and safety improvement efforts. The effort restored proper fluvial process, protected public infrastructure and improved safety.
