Uncompahgre River Channel Stability Study, Colorado

Mussetter Engineering, Inc. (MEI) performed an analysis of the geomorphic, hydraulic, and channel stability conditions in an approximately 30-mile reach of the Uncompahgre River between Montrose and Delta, Colorado, to support a Section 404 permit application for the proposed AB Lateral Hydropower Project. The primary focus of the study was to evaluate the potential effects to channel stability of changes in flow regime associated with the hydropower project.

Three flow scenarios were considered in the analysis, including the no-project alternative and two different hydropower plant capacities. The analysis included a detailed field reconnaissance of the project reach, and HEC-2 hydraulic analysis to estimate the flow velocities, depths, and other important hydraulic characteristics of the study reach for the range of flows affected by project operations, an evaluation of the conditions required to transport existing bed material, and an evaluation of the potential for lateral erosion and channel widening. The analysis also included an assessment of the hydraulic energy available to erode the channel banks at 83 individual sites along the reach using the Bank Energy Index (BEI) concept developed by Dr. Mussetter. The BEI results were used to develop criteria for selecting sites that may require mitigation measures under project operations.

MEI also performed a separate verification study of an approximately 2.5-mile reach of the Uncompahgre River located approximately 5 miles upstream of Montrose that had experienced flows similar to those anticipated to occur under project conditions. The channel characteristics in the verification reach were shown to be very similar to those predicted to develop in the project reach under the proposed project conditions.

Major Project Features

• HEC-2 Hydraulic analyses
• Fluvial geomorphic analyses
• Routing of floods through river channels
• Development of water surface profiles
• Sediment studies
• Bank erosion analysis