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American River Watershed Project




American River Common Features Folsom Dam Modifications Folsom Dam Raise Folsom Dam Bridge


Old Sacramento photo
The American River gave birth to Sacramento
with the discovery of gold in 1848.

Ever since then the river has been trying
to take the city back.

People hoping to get rich selling goods to gold miners, built Sacramento at the confluence of the American and Sacramento Rivers. The Sacramento River brought the miners up from San Francisco, and the American held the promise of riches. Both rivers also held the promise of ruin from their floodwaters. Native Americans knew the Sacramento Valley as an inland sea when the rains came. Ancient storytellers told of water filling the valley from the Coast Range to the Sierra.

Folsom's First Dam 1889

Almost as soon as they completed their homes and businesses, the settlers began a battle that continues today to control the inland sea. They started with small levees along the rivers. When the levees couldn't’t hold back the floods, they raised their homes and businesses one story to get them out of the floodwaters.

As gold miners turned to farming and settlers moved into the Sacramento Valley, they began looking for better ways to hold back the rivers. The Corps of Engineers’ Sacramento District and the California Reclamation Board developed the first major flood control projects west of the Mississippi in the early 20th Century. They built flood control levees and developed a bypass system along the Sacramento River. The bypass allowed floodwater to escape from the river and flow safely around towns and farms. Soon, engineers built dams on the Sacramento and American Rivers and many of their tributaries.

With each reduction in the flood threat, new towns sprang up along the rivers, cities bulged, and people moved into floodplains. Then came the record storm of 1986, and Sacramentans realized just how vulnerable they are to flooding. Sacramento has one of the highest flood risks of any river city its size in the United States.

Storm data shows that the largest storms of record have occurred over the last 50 years. With each large storm, the flood risk has increased, and Sacramento currently has a 1 in 85 chance of flooding in any given year. To help find ways to reduce the flood risk, local governments formed the Sacramento Area Flood Control Agency (SAFCA) to work with the California Reclamation Board, the Department of Water Resources (DWR), and the Army Corps of Engineers.

The people of Sacramento want at least a 200-year level of flood protection (that’s a 1 in 200 chance of flooding in any given year). The American River Watershed Projects developed by the Corps, SAFCA, the Reclamation Board, and DWR will provide at least that level of protection.



Gold discovered in the American River above Sacramento.
The gold rush begins and settlers flock to Sacramento.
Major flooding in the fledgling city marks the start of flood control efforts.
Hydraulic gold mining begins. Millions of cubic yards of debris washed downstream clogging rivers over next several years.
Courts halt hydraulic mining.
Congress allows hydraulic mining to resume under the control of the newly created California Debris Commission. The Commission consists of three Corps of Engineers officers.
The entire Sacramento Valley is flooded.
The entire Sacramento Valley flooded again.
Corps of Engineers sends comprehensive flood control report to congress.
Congress authorized flood control work in the Sacramento River basin (first time congress authorized flood control work outside the Mississippi Valley).
Congress makes Corps responsible for flood control nationwide.
Congress authorized the Corps to raise, dig, lengthen, widen, and straighten a system of levees and channels.
Congress authorized Corps to build Folsom and other dams, build levees and channels.
Approximately 107 miles of levees built in the northern end of the Sacramento valley.
The nearly completed Folsom Dam saves Sacramento from devastating flooding that nearly destroys Yuba City.
The storm of Record for Sacramento, and the beginning of the current efforts to reduce the area’s flood risk.
Corps sends flood control study to congress. Congress directs Corps to construct an interim flood control project to quickly reduce the flood risk. The project includes:
• 24 miles of slurry walls 15-40 feet deep along American River
• 12 miles of levee work along Sacramento River
• Gages and flood warning system construction
• $56.9M authorized cost
Near storm of record causes unexpected levee foundation damage and changes the design of the common features flood control work. New design includes:
• Deepening slurry walls to 60-80 feet.
• Adding slurry walls at bridges & utility crossings.
Congress authorizes additional work:
• 3 miles of additional American River levee work
• 10 miles of Natomas Crossing levee work
• $91.9M authorized cost
Completed and on-going work (Common Features Project):
• 19 miles of slurry wall levee work completed
• Bridge & utility crossing work in progress
• Natomas Basin work being evaluated to determine most cost effective measures
Submit feasibility study to Congress (Summer 2005)
• New work in Natomas Basin and South Sacramento sites
• $65M to $165M cost estimate