From the Document: "Congress often titles omnibus legislation that authorizes U.S. Army Corps of Engineers (USACE) civil works activities and directs the agency's practices as a Water Resources Development Act (WRDA). WRDAs are distinguished from each other by referencing the year of enactment (e.g.,WRDA 1986). WRDA provisions generally add to or amend the pool of existing USACE authorizations andrefine policy direction that Congress provides to the agency.Other provisions may deauthorize inactive unconstructed projects.Although the majority of USACE authorizations do not expire, some are time-limited. WRDA provisions also may extend time-limited USACE authorities. Most USACE water resource projects require two types of congressional authorization: one for studying feasibility and a subsequent one for construction. Drivers for enactment of a new WRDA typically include nonfederal and congressional interest in new studies and construction projects and support for adjustments to existing projects, programmatic authorities, and policies. Since WRDA 1986, Congress often has considered WRDA legislation on a biennial cycle; however, the timing of enactment of WRDAs has varied."
CRS In Focus, IF11322
Congressional Research Service: https://crsreports.congress.gov/