Water Resources Collections and Archives

Saeltzer Dam was removed from Clear Creek in October 2000 to restore ten miles of upstream habitat access to spring run chinook salmon and steelhead trout. Since the dam removal, an estimated 50,000 cubic yards of sediment has eroded from the banks and channel at the former dam site. Some of the eroded sediment has been deposited downstream on Renshaw’s Riffle, a stretch formerly known for its spawning habitat, aggrading the bed up to 2.5 ft. To evaluate characteristics of the sediment deposition, we performed roughly 60 pebble counts and created a facies map for a 1.43 mi stretch downstream of the former dam site. We created maps in ArcMap GIS using the data to depict changes in gravel bar location, the d50 (the size at which 50% of the pebbles are finer) and the composition of percent-finer-than-8 mm material for each pebble count along the length of our study area. Five pebble counts were performed at transects in Renshaw’s Riffle, at sites with existing cross-sectional data. We found that finer-than-8 mm sediments comprise over 20% of the substrate in parts of the riffle. An earlier facies map was created in 2001 by visual assessment, but we were unable to compare our results due to incompatible methods. We hope the pebble count serves as an easily replicable method from which to compare future surveys of the area.