Levee: A man-made structure, usually an earthen embankment or concrete floodwall, designed and constructed in accordance with sound engineering practices to contain, control, or divert the flow of water so as to provide reasonable assurance of excluding temporary flooding from the leveed area.

Levee Segment: A discrete portion of a levee system that is operated and maintained by a single entity. 

Levee System: One or more levee segments and other features such as floodwalls and pump stations, which are interconnected and necessary to ensure exclusion of the design flood from the associated leveed area. 

Leveed Area: The lands from which flood water is excluded by the levee system. 

It is a common misconception that USACE manages all levees in the nation. In reality, the levees included in the USACE Levee Safety Program represent only about 10 percent of the nation’s levees (as estimated by the National Committee on Levee Safety). However, more than 10 million people live or work behind USACE program levees.  For this reason, USACE considers its role in assessing, communicating and managing risk to be a top priority. There are many miles of private-party, federal, state and local levees outside the Corps’ inspection program. Presently, there is no universal oversight of levees in the nation.

Several classes of levees exist within the Portland District area of responsibility, with differing degrees of federal involvement:

• Levees built, operated and maintained by the federal government;
• Levees built by the federal government and then turned over for operation and maintenance by a local sponsor;
• Levees constructed by a non-federal entity and are enrolled in the USACE's Rehabilitation and Inspection Program; and 
• Levees that were neither built by the federal government nor are part of federal operations or maintenance programs. 

The National Levee Database (NLD) is the authoritative resource for information about levees in the United States. You can use the NLD to learn about levees in the United States. With the NLD’s easy-to-use and highly functional tools, you can find levees and learn about their purpose and impact on the surrounding area. The NLD provides easy access to comprehensive levee information resources including flood risk communication, levee system evaluation for the National Flood Insurance Program (NFIP), levee inspections, flood plain management, and risk assessment. The NLD is intended to be a primary information resource for federal, state and local governments, agencies, and organizations, as well as the general public.

The Federal Emergency Management Agency administers the National Flood Insurance Program, which reduces the socio-economic impact of disasters by providing affordable insurance to property owners, renters and businesses and by encouraging communities to adopt and enforce floodplain management regulations.

Eligible levees, to a reasonable degree of certainty, will protect the area from the base regulatory flood, which has a 1% chance of occurring in any given year (sometimes called a 100-year flood). Certification of levees for the National Flood Insurance Program is the responsibility of the local levee owner or sponsor. If levee certification documentation is found to be in order, FEMA has the authority to accredit the levee and the associated flood insurance rate maps.

In some cases, USACE's Levee Safety Program activities can help inform and support the initial certification process, but USACE does not have specific authority to conduct these levee certifications. For more information on NFIP, visit FEMA's website.