American River History
Folscom Dam Modificiations
Folsdom Dam Raise
Folsdom Dam Bridge
In the News
American River Common Features
The American River Common Features Project involves significant levee
improvements on the American River and Sacramento River, as well as in
the Natomas area. When completed in late 2004, the work on the American
River levees will reduce a portion of the Sacramento area’s flood
risk to 1 chance in 100 in any given year. Additional work has been completed
on Sacramento River levees and in the Natomas Basin, and more levee work
is in the planning stages for these areas.
The American River Common Features Project is part
of the integrated Watershed Project to reduce the risk of flooding in
the Sacramento area to a 1-in-213 chance in any one year. This overall
effort also includes modifications to the outlet gates at Folsom Dam and
the Folsom Dam Raise.
Soon after the record storm of 1986, the Army Corps of Engineers (Corps),
California Reclamation Board (Reclamation Board) and the Sacramento Area
Flood Control Agency (SAFCA) formed a partnership to find ways to reduce
Sacramento’s flood risk.
At one time the Corps, Reclamation Board,
and SAFCA proposed a flood control dam near Auburn along with the levee
improvements downstream of Folsom Dam. There was no community consensus
for the dam, and Congress told the Corps to focus instead on the downstream
flood control system, and to combine a number of features common to three
different flood management proposals into one plan to reduce the flood
risk to Sacramento.
The result is the
American River Common Features Project, a comprehensive effort that includes
levee work on the Lower American River, levee work on the east bank of
the Sacramento River adjacent to downtown, levee work in the Natomas Basin,
additional upstream river flow gages, and an improved flood warning system
along the lower American River.
These common features are an interim measure to reduce the flood risk.
Future measures include modifying the outlet gates at Folsom Dam and raising
Folsom Dam so that it can hold back additional floodwater.
The main element of the originally authorized common
features project was to install an impervious barrier along almost 20
miles of American River levees. The barrier consists of a mixture of soil,
clay, cement, and water, called a slurry cut-off wall. Other elements
- Installing additional stream flow gauges along
the upper American River to more accurately assess flows into Folsom
- Improving the network of sirens used to warn
people of potential flooding along the lower American River.
- Raising the left bank of the non- Federal levee
upstream of the Mayhew Drain by an average of 2.5 feet for a distance
of 4,500 feet.
- Raising the right bank of the American River
levee by an aver- age of one foot from 1,500 feet upstream to 4,000
feet down stream of the Howe Avenue Bridge.
- Modifying the south levee of the Natomas Cross
Canal for a distance of 5 miles to ensure that the south levee level
of protection is consistent with that provided by the authorized levee
along the east bank of the Sacramento River.
- Modifying the north levee of the Natomas Cross
canal for a distance of 5 miles to ensure that its height is equivalent
to the height of the south levee.
- Installing gates to the existing Mayhew Drain
culvert and pumps to prevent backup of floodwater on the Folsom Boulevard
side of the gates.
- Installing a slurry wall in the north levee
of the American River from the east levee of the Natomas East Main Drain
upstream for a distance of approximately 1.2 miles.
- Installing a slurry wall in the north
levee of the American River from 300 feet west of Jacob Lane north for
a distance of approximately one mile to the end of the existing levee.
Army Corps of Engineers Sacramento District
The Reclamation Board
State of California
Flood Control Agency
A city dealing with its flood risk
After more than 150 years of struggling to keep the American
and Sacramento Rivers out of their homes and businesses, the people of
Sacramento now have comprehensive plans in the American River Common Features,
Folsom Dam Modification, and Folsom Dam Raise projects to reach the level
of flood protection an important city such as Sacramento must have.
Since the record floods of 1986, engineers have developed
more sophisticated tools for collecting information on storms and on the
effects of high flows on levees, as well as methods to analyze this information.
Flood control engineers today know much more about the conditions of the
American and Sacramento River levees and how to strengthen them than when
they started their efforts to reduce Sacramento’s flood threat several
years ago. The benefit of these advances is better flood protection. The
most significant of these advances is deeper slurry walls, jet grouting,
and stronger levees. As the engineers learned more about the flood control
system so critical to protecting the people of Sacramento, they also saw
the amount and cost of the work to protect the community increase.
Costs for the project changed mainly as a result of improvements
in technology, newer methodologies, and due to an increase in the amount
of work. When Congress authorized the levee improvement work in 1996,
the Corps estimated the cost at $56.9 million. In 1999, Congress authorized
additional work increasing the estimated cost to $91.9 million. The Corps
and its flood control partners now estimate that it will cost $205 million
to accomplish the levee work needed to reduce Sacramento’s flood