Clear Creek Geomorphic Monitoring
Clear Creek is a tributary to the Sacramento River and was historically a major salmon and steelhead producing stream. Construction of Whiskeytown Dam, Saeltzer Dam, gold mining and gravel extraction have significantly reduced the magnitude and frequency of natural fluvial geomorphic processes that are necessary to maintain healthy ecological functions. Gravel excavation and gold dredging removed point bars, floodplains, and riparian vegetation, leaving behind open extraction pits and a channel that was braided in some reaches and confined between dredger tailings in others. Bedrock exposure throughout the reach severely impaired alluvial and ecological function.
The overall geomorphic objective on lower Clear Creek was to create or facilitate a single thread channel morphology that was properly sized to the anticipated future sediment transport and flow release regimes. Restoration actions toward this objective included: lowering floodplains and planting with native vegetation, removal of confining tailings, filling off channel pits, resizing and relocating the channel within its floodplain and implementing gravel injections.
The Clear Creek Restoration Team developed two basic questions to be addressed by geomorphic monitoring: (1) Are natural geomorphic processes being restored by the projects, and (2) How is the channel location and morphology adjusting during high flow events? The first question addresses project performance as it relates to ecological and geomorphic restoration objectives, while the second addresses how well the channel was built by targeting critical channel locations most susceptible to undesired channel adjustment. GMA has continuously monitored various phases of restoration on Clear Creek since 2002. Monitoring efforts include: stream gaging (discharge and turbidity), sediment transport monitoring (suspended sediment and bedload discharge), channel geometry (cross sections, long profiles, topography), sediment transport charatcteristics (bed mobility thresholds, claypan exposure), and geomorphic assesments (riparian encroachment, spawning gravel supply, channel evolution).
Restoration success varies by reach. More of the creek now functions a dynamic alluvial stream, floodplains are more frequently inundated, groundwater levels are higher, claypan is less exposed, riparian diversity and vigor has increased and salmonid habitat has increased.