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.
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
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