Canyon Creek Meadows Dam Evaluation (OR)
Canyon Creek Meadows Dam is located within the Malheur National Forest approximately 15 miles south-southeast of John Day, Oregon. The existing dam experiences significant leakage and poses a risk of failure if not repaired. WEST Consultants was contracted to evaluate the hydrologic, hydraulic, and geomorphic impacts associated with both repair and removal of the dam.

A HEC-HMS hydrologic model of the Canyon Creek Basin was developed to define the hydrology of the basin. The continuous simulation capability of HEC-HMS was utilized to perform flood frequency analysis and flow duration characterization of the existing condition, repair and removal scenarios.

A hydraulic analysis associated with a potential breach of the Canyon Creek Meadows Dam was performed. The analysis used HEC-RAS to develop an unsteady dam breach simulation model and defined the resulting flood water levels downstream of the dam location.

A qualitative geomorphic evaluation was conducted identifying the controlling geomorphic processes of the existing condition and defining the expected geomorphic response to the proposed alternatives. The study included the characterization and volume estimation of sediment deposits which have accumulated within the reservoir area. Potential impacts evaluated from dam removal included headcut erosion of the channel bed, bank erosion, and downstream aggradation due to the release of stored sediments.