River Restoration Plan for the San Miguel River, Colorado

Mussetter Engineering, Inc. (MEI) performed geomorphic, hydrologic, hydraulic, and sediment transport analyses of an approximately 1.5-mile reach of the San Miguel River in Telluride, Colorado, to support the development of a comprehensive plan to restore severely impacted aquatic, wetland, and riparian habitats along the river corridor. The river corridor through the town has been altered significantly over time by a variety of factors including channelization, sediment deposition, heavy metal loading, in-channel sand and gravel mining, and encroachment of the channel by urban development.

MEI performed a detailed field reconnaissance of the project reach and a geologic and geomorphic evaluation to identify significant problems and potential solutions. A hydraulic analysis using HEC-RAS was conducted to evaluate hydraulic conditions (water-surface elevations, depths, velocities and other important hydraulic characteristics) for a range of flows up through the 100-year event. Incipient motion analysis and a sediment continuity analysis using the Parker sediment transport function were conducted to characterize sediment transport conditions in the project reach. The analyses of existing conditions showed that bridge crossings, local constrictions due to urban development, and an overly wide channel were all contributing to sedimentation problems in the project reach. The resulting wide and shallow flow was limiting in-channel aquatic habitat for salmonid species.

Based on the results of the analyses of existing conditions, a restoration plan for the channel was developed. The plan addressed the sedimentation problems, provided improved hydraulic conditions for aquatic habitat, and minimized impacts to the flood conveying function of the channel. The sedimentation problems were addressed in the plan by controlling the upstream supply of bed-material load with a sedimentation pond located at the head of the project reach and improving the transport capacity of the reach by removing local constrictions and creating a narrower and deeper low-flow channel. Riffles, pools, and step-drop structures were included in the design to improve aquatic habitat. The plan was developed considering Federal Regulations under the National Flood Insurance Program.

Major Project Features

• Hydrologic analysis
• Fluvial geomorphic analysis
• Development of a channel restoration plan
• Hydraulic analysis using HEC-RAS
• Sediment transport analysis
• Development of hydraulic design criteria