The branch of archaeology devoted to studying artifacts and features on sites which are imminently threatened by development in the form of the construction of dams, buildings, highways, etc. Threats to archaeological remains occur in the form of road-building, road improvement, new building of houses, offices, and industrial complexes, the flooding of valleys for reservoirs, and improved farming techniques involving the use of deep plowing. The rescue, or salvage, archaeologist, is concerned with the retrieval of as much information as possible about the archaeological sites before they are damaged or destroyed. Frequently time is too short and funds are too limited for anything but a brief survey. Salvage archaeology is the location, recording (usually through excavation), and collection of archaeological data from a site in advance of highway construction, drainage projects, or urban development. In the US, the first major program of salvage archaeology was undertaken in the 1930s, ahead of the construction and dam building done by the Tennessee Valley Authority.