The city's location puts it among the U.S. cities most vulnerable to significant flooding. Potential flood losses grow as development in the area places more lives and properties in harm's way. To reduce flooding risks in Sacramento, local, state, and federal entities have built dams, levees, and other structures, including the federally constructed Folsom Dam on the American River. Following a significant flood threat in 1986, Congress in 1987 authorized the U.S. Army Corps of Engineers (Corps) to study additional flood damage reduction measures (e.g., dam and levee improvements, construction of new structures, adoption of operational improvements). This report outlines the status of these studies and measures, with particular attention to measures at Folsom Dam. Historical Efforts to Reduce Flood Vulnerability

Sacramento has historically been prone to flooding. Recent studies using a more comprehensive picture of the city's flood risk place the city's flood protection at less than the 100-year level (i.e., a greater than 1% annual probability of a flood affecting the city). Recent growth in the Sacramento area may increase flooding damages. Since 1992, Congress has authorized construction of physical modification projects to improve flood protection around Sacramento and Folsom Dam, including (1) the Common Features Project that consists of levee improvements on the American and Sacramento Rivers; (2) the Folsom Dam Modification that entails changes to the flood gates and spillway of Folsom Dam; and (3) the Folsom Dam Raise that elevates the concrete and earth portions of the dam, provides for the construction of a permanent bridge, and authorizes other related measures. The feasibility study was directed to define flood risks and develop potential projects to increase flood protection in the American River watershed. Auburn Dam Renewed Debate

The congressional debate over Sacramento flood protection continues to include Auburn Dam. Congress approved additional appropriations in the Energy and Water Development Appropriations Act of FY2006 for an updated study on Auburn Dam (often referred to as the Auburn-Folsom South Unit), reviving debate on this subject. Concluding Remarks

How to reduce flood risks in developed and developing areas is a problem being faced by communities nationwide, and is receiving increased attention as the reliability of existing infrastructure is reevaluated in the aftermath of Hurricane Katrina. In the last half century, the dam and levee system around Sacramento has proved crucial in protecting the city from flooding. Recently, the federal government has authorized three major flood protection improvement projects in the Sacramento area. These include improvements to Folsom Dam's operational rules, improvements to the American and Sacramento Rivers and Natomas Basin levees, as well as modifications to Folsom Dam's flood gates and a raise of the dam itself. Some of the federally authorized improvements involving fortification of the American and Sacramento River levees are under construction or completed, while others are undergoing reevaluation.
Sacramento, California, is among the U.S. cities most vulnerable to flooding, and regional growth is increasing the potential losses from flooding. A major flood could inundate developed and agricultural areas, disrupting the economy and damaging infrastructure and property. How to reduce flood risks in developed and developing areas is a problem faced by communities nationwide, and is receiving increased attention as the reliability of existing infrastructure is reevaluated in the aftermath of Hurricane Katrina.
Sacramento's flood protection system, which includes levees on the American and Sacramento Rivers as well as Folsom Dam on the American River, has been crucial in protecting the city over the last 50 years. Storms in 1986 and 1996 prompted increased attention to Sacramento flood concerns from the federal government, which subsequently has contributed efforts to reduce the city's flood vulnerability.
Beginning in 1987, Congress authorized and appropriated funds for several studies by the U.S. Army Corps of Engineers (Corps) to investigate flood protection in the Sacramento area. These studies showed that the city's flood damage reduction system provided less than 100-year flood protection (i.e., a greater than 1% annual chance of flooding). The studies suggested a number of options to augment flood protection, including improvements to local levees, various changes and additions to the federally constructed Folsom Dam, and a dam upstream from Folsom Dam on the American River (Auburn Dam).
Since 1992, Congress has authorized a variety of actions, including improving levees and modifying Folsom Dam. Although Congress authorized plans to expand Folsom Dam's capacity to regulate larger floods, some planned activities have become problematic due to changes in cost estimates. Current studies are exploring additional potential options addressing flood control in the area. Congress is likely to revisit issues relating to authorization, cost, and oversight of Sacramento flood protection projects. Reconsideration of Auburn Dam on the American River (also known as the Auburn-Folsom South Unit) or another dam near the Auburn site also may be debated.
In addition to structural changes at Folsom Dam, Congress also has authorized and implemented dam operational changes. Some actions to rehabilitate and improve levees on the American and Sacramento Rivers are currently under construction; others have been delayed and are undergoing reevaluation.
This report briefly outlines recent major federal involvement in flood control in the Sacramento region of California, with particular attention to recent changes and developments in the construction of projects at Folsom Dam. It outlines recent congressional and agency actions intended to strengthen flood control in this region, and provides an update on the status of these actions.