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


Flood Dam Raise
Folsom Dam and a system of levees protect the Sacramento area from American River flooding. The American River watershed covers approximately 2,100 square miles northeast of Sacramento and includes portions of Placer, El Dorado, and Sacramento counties. Runoff from the watershed flows through Folsom Reservoir and passes through Sacramento in the American River.

Foslom Dam

The Folsom Dam Raise project is the final component of the overall American River Watershed project. The main part of the project involves raising the existing dam approximately 7 feet. The project also includes enlarging the spillway at L.L. Anderson Dam, ecosystem restoration and habitat improvement, and building a permanent bridge for Folsom Dam.

Raising Folsom Dam is a key component in reducing Sacramento’s flood risk. The dam and other water resource developments in the basin are responsible for regulating flows in the Lower American River. Raising the dam will increase the amount of storage and in return will increase Folsom Dam’s ability to control larger floods.

Widespread flooding along the American River would cover approximately 86 square miles of the developed Sacramento area, and potentially affect 330,000 people and $29 billion in property.

Although recent and ongoing work to improve levees on the Lower American River and modifications planned for Folsom Dam will reduce the risk of flooding, the risk remains higher than is acceptable to the people of the Sacramento area. They have stated that they want to reduce their flood risk to less than a 1-in-200 chance of flooding in any given year. Raising Folsom Dam, along with other American River Watershed project components, will achieve that goal.

A city at risk
Sacramentans realized the need to decrease their flood risk in February 1986 when record storms in northern California caused major flood flows in the American River. Outflows from Folsom Dam, together with high flows in the Sacramento River, caused the river stages to exceed the safety margin of the levees protecting the city of Sacramento. As a result, emergency repair work was required at several locations to keep the levees from failing. If these storms had lasted much longer, major sections of the levee likely would have failed, causing probable loss of human life and billions of dollars in damages.

In January 1997, extreme rainfall in the Upper American River watershed again revealed the need for increased flood protection.

The effects of the 1986 and 1997 storms raised concerns over the adequacy of the existing flood control system. This led to a series of investigations of the need to provide additional protection for the Sacramento metropolitan area.

The plan to raise Folsom Dam is the result of these recent investigations. It is a major step in the effort to protect the hundreds of thousands of people and billions of dollars of property in the Sacramento flood plain.

n Dam raise reduces flood risk
n Enlarger L. L. Anderson Dam Spillway
n Ecosystem restoration and habitat improvement
n Mooney Ridge infrequent inundation


US Army Corp of Engineers Logo
US Army Corp of Engineers
Sacramento District
US Bureau of Reclamation Central California Area Office Logo
US Bureau of Reclamation
Central California Area Office
Reclamation Board State of California Logo
The Reclamation Board
State of California

Sacramento Area Flood Control Agency Logo
Sacramento Area
Flood Control Agency
Placer County Water Agency Logo
Placer County Water Agency
City of Folsom Logo
City of Folsom
  Independent analysts found dam raise safe
  A team of independent analysts reviewed the Corps’ proposal to raise Folsom Dam and found that the Corps can safely raise the dam to help reduce Sacramento’s flood risk.

The team concluded that the dam would need some modifications to accommodate the raise, and they recommended that the Corps further analyze the interface between the dam’s foundation and the bedrock and perform some additional stabilization work on the project.