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| American River floods | |
|---|---|
| Name | American River |
| Country | United States |
| State | California |
| Length | 120 mi |
| Basin | Sacramento River watershed |
American River floods
The American River floods have been recurrent hydrological events on the American River (California) affecting the Sacramento–San Joaquin River Delta, Sacramento County, California, Placer County, California, El Dorado County, California and the City of Sacramento; notable inundations have involved responses by agencies such as the United States Army Corps of Engineers, the California Department of Water Resources, the Federal Emergency Management Agency, the California Office of Emergency Services and the National Weather Service. Major historical floods intersect with projects like the Central Valley Project, the California State Water Project, and infrastructure investments including Folsom Dam, Nimbus Dam, Lake Natoma, Folsom Lake State Recreation Area and the American River Parkway; scholarly and municipal analyses appear in reports from the University of California, Davis, the US Geological Survey and the California Department of Water Resources.
The American River (California) rises on the western slope of the Sierra Nevada (United States), draining headwaters near Desolation Wilderness, Tahoe National Forest, Eldorado National Forest and the Granite Chief Wilderness into confluences at North Fork American River, Middle Fork American River, and South Fork American River before meeting the Sacramento River in Sacramento, California. The basin architecture includes tributaries such as Silver Fork American River, Crystal Basin, North Fork American River (tributary), glacial and snowpack inputs from Sierra Nevada snowpack, seasonal modulations by Pacific storm tracks and orographic precipitation influenced by the California Current and the Pacific Decadal Oscillation. Hydrologic monitoring occurs at gauges operated by the United States Geological Survey, the California Department of Water Resources, and flood forecasting centers of the National Oceanic and Atmospheric Administration and the National Weather Service.
Historic inundations on the American include major nineteenth and twentieth century episodes tied to the Great Flood of 1862, the 1911 California flood events, the Flood of 1955 and high-flow periods during the California floods of 1986–1987 and the New Year’s flood of 1997 (California), with emergency declarations from the State of California and federal disaster declarations under the Robert T. Stafford Disaster Relief and Emergency Assistance Act. The catastrophic winter of 1861–1862 transformed river hydrodynamics noted by contemporaneous sources in Sacramento (city), Coloma, California and Sutter's Fort (California), while twentieth-century episodes prompted infrastructure responses led by the United States Army Corps of Engineers and planning by the California Department of Water Resources and municipal agencies in Sacramento County and Placer County.
Flooding on the American River results from combinations of atmospheric rivers originating over the North Pacific Ocean, rapid snowmelt from the Sierra Nevada (United States), prolonged precipitation events influenced by the El Niño–Southern Oscillation and the Pacific Decadal Oscillation, and land-use changes in watersheds across El Dorado County, California, Placer County, California and Sacramento County, California. Human alterations including the construction of Folsom Dam, Nimbus Dam, levees by the United States Army Corps of Engineers, floodplain development in Sacramento (city), and historical hydraulic mining impacts near Coloma, California and Gold Rush era sites have modified sediment regimes and conveyance capacity, documented by researchers at University of California, Berkeley, California State University, Sacramento, and the US Geological Survey.
Flood episodes have inundated neighborhoods in Sacramento, California, disrupted transportation on the Interstate 80 (I-80), U.S. Route 50 (California), and local crossings, damaged critical assets including Folsom Dam facilities, Folsom Lake State Recreation Area amenities, and the American River Parkway; impacts have required mobilization by local jurisdictions such as the Sacramento County Office of Emergency Services, Placer County Sheriff’s Office, and state agencies including the California Highway Patrol and the California Department of Transportation. Economic losses have been estimated in reports commissioned by the Metropolitan Water District of Southern California, the Sacramento Area Council of Governments, and private insurers such as Allianz and State Farm, while social effects have prompted involvement by nonprofit organizations like the American Red Cross, Community Housing Improvement Program (CHIP), and faith-based groups in recovery.
Flood mitigation on the American River comprises structural and non-structural measures including construction and operation of Folsom Dam and Nimbus Dam by the United States Bureau of Reclamation and United States Army Corps of Engineers, levee systems engineered in coordination with the California Department of Water Resources, bypasses and setback levees planned by the U.S. Army Corps of Engineers Sacramento District, and land-use planning by Sacramento County, California and Placer County, California agencies. Complementary measures include floodplain restoration projects supported by the California Department of Fish and Wildlife, early warning systems from the National Weather Service, emergency management led by the Federal Emergency Management Agency, and local resilience initiatives involving Sacramento Municipal Utility District and regional water agencies.
Flood dynamics influence riparian corridors along the American River, affecting habitat for species protected by the Endangered Species Act such as Chinook salmon, steelhead trout, and ecological communities managed by the California Department of Fish and Wildlife and the U.S. Fish and Wildlife Service. Sediment transport and legacy pollutants from hydraulic mining during the California Gold Rush altered channel morphology and mercury loading addressed in studies by the US Geological Survey and University of California, Davis. Restoration projects at sites including American River Parkway and Folsom Lake State Recreation Area involve partnerships with The Nature Conservancy, local land trusts, and academic programs at California State University, Sacramento.
Projected changes in precipitation patterns and snowpack in the Sierra Nevada (United States), influenced by scenarios from the Intergovernmental Panel on Climate Change and regional climate models produced by the California Climate Change Center, indicate altered flood seasonality and increased risk of high-magnitude floods; agencies such as the California Department of Water Resources, United States Geological Survey, and National Oceanic and Atmospheric Administration are integrating projections into planning for Folsom Dam operations, levee upgrades, and floodplain management by Sacramento County, California and Placer County, California. Adaptation strategies being evaluated include nature-based solutions promoted by The Nature Conservancy, infrastructure resilience funding through the Federal Emergency Management Agency and Department of Homeland Security, and coordinated regional planning by the Sacramento Area Flood Control Agency and the Sacramento-San Joaquin Valley Conservancy.
Category:Rivers of California Category:Floods in the United States Category:Sacramento County, California