Sediment Transfer through the Fluvial System (Proceedings of a symposium held in Moscow, August 2004). IAHS Publ. 288, 2004, 235–244

Abstract Suspended sediment loads in large rivers are increasing globally, but this trend has reversed in some basins due to dam construction, particularly in developed countries. Sediment loads in lower Sacramento Valley basins began decreasing by 1900 (as shown by G. K. Gilbert’s classic 1917 study of hydraulic gold-mining debris), preceding most USA reductions by up to 50 years. From 1853 to 1884, hydraulic mining generated >3.7 billion tonnes of tailings with specific sediment productions up to 16 807 t km^-2 year^-1. Double-mass curves of post-1950 suspended sediment and runoff indicate decreasing sediment responses to streamflow in the lower Sacramento and Feather Rivers continued through the late 20th century. Independent evidence indicates that these reductions were caused by dam closures and the reduced availability of historical alluvium stored below the dams.

Key words historical alluvium; Sacramento Valley, California; suspended sediment; trends