Hydraulic gold mining in the Sierra Nevada, California (1853–1884) displaced ~1.1 billion m of sediment from upland placer gravels that were deposited along piedmont rivers below dams where floods can remobilize them. This study uses topographic and planimetric data from detailed 1906 topographic maps, 1999 photogrammetric data, and preand post-flood aerial photographs to document historic sedi...