US 34 Big Thompson Canyon Permanent Repair Hydraulics

« Return to Project Search

US Highway 34 suffered extensive damage during the September 2013 flooding on the Big Thompson River. Ayres assisted with hydraulic analysis and design for the permanent repairs.

The project won Engineering News-Record’s 2018 Project of the Year Award (its top award in the nation) and ENR’s 2018 Best of the Best Highway/Bridge Project Award. The Colorado Association of Stormwater and Floodplain Managers (CASFM) gave the project its 2019 Engineering Excellence Grand Award.

Ayres performed geomorphic and hydraulic field assessments of the roadway corridor and converted the HEC-2 segments of the effective Larimer County 1-dimensional regulatory models to a single HEC-RAS model of the study reach. Ayres developed pre-flood and existing conditions 2-dimensional SRH hydraulic models of the US 34 corridor along the Big Thompson River between Olympus Dam in Estes Park and Rossum Drive in Loveland, Colorado.

This modeling provided detailed velocity, water surface elevation, and shear stress data for the 24-mile reach and supported channel rehabilitation design, proposed roadway alignment and profile development, roadway repair scour protection, scour countermeasure design, and floodplain regulatory compliance. The flood conditions within the canyon are uncommonly severe, with the 100-year flood producing velocities exceeding 20 feet per second in some locations. These severe conditions required innovative design and construction for the highway embankment protection.

Project Information

Client's Name

Colorado Department of Transportation, Headquarter Office


Larimer County, CO

Primary Service

River Engineering + Water Resources


State + Federal + Tribal