Confluence prepared preliminary designs to restore Teton Creek following severe, illegal channelization of the stream bed by a previous landowner.  Designs included elevating the incised stream bed to near historic elevations and widening the floodplain to contain the estimated 100 year flow.  A hydrologic analysis was performed to estimate channel-forming flows (bankfull and effective discharges).  Hydraulic (HEC-RAS) modeling was used to map flood elevations and estimate incipient motion for the beds and banks.  The model was used as a basis for enlarging a county road bridge to reduce flooding of upstream homes.

Confluence also directed pre-restoration data collection efforts and played a significant advisory role in steering restoration efforts through technical and public meetings.  Confluence specialists developed guidelines for collecting bank erosion, vegetation composition, bed composition, and hydrologic data for use in conceptual design and planning.  Bank erosion analysis included using the BEHI method for prioritizing restoration efforts based on sediment loads from individual banks.  Successful data collection efforts proved extremely useful in developing appropriate designs for channel and floodplain restoration along the 1.5 mile project reach.

Flood map for Teton Creek showing estimated flood boundaries

 

Teton Creek wtihin the Moses headcut reach. Note: gravel pitted on banks by previous illegal excavation.