Channel response to dam removal, Clear Creek, California

Clear Creek drains 720 km2, joining the Sacramento River south of Redding, California. The 4.6-m high Saeltzer Dam blocked upstream migration of chinook salmon (Oncorhynchus tshawytscha) since it was built in 1912 to divert water for irrigation. Saeltzer Dam was removed in 2000 to restore anadromous fish access to upstream reaches. Before the dam was taken down, 19,000 m3 of sediment stored behind the dam was mechanically removed, but substantial deposits remained. A 2001 survey (Stillwater Sciences and University of California Davis 2001) detected little channel change in the former reservoir area over the 2001 flow season (peak flow 35 m3s-1). We resurveyed the channel in 2003 (peak flow 130 m3s-1). Our survey documented post 2001 incision of more than 1 m, over about 320 m upstream of the former dam site to an active headcut, and lateral erosion of 15-18 m, for total erosion of over 3000 m3 from the former reservoir deposit. Dam removal has led to desiccation of riparian trees (mostly Alnus spp.), with over 50 trees visibly dead or dying, and lateral bank erosion has removed more trees.