Reservation land is held “in trust” for Native Americans by the federal government … In 1938, the U.S. Army Corps of Engineers flooded 600 acres of tribal land to build lock and dam 3. That land …Reservation land is held “in trust” for Native Americans by the federal government … In 1938, the U.S. Army Corps of Engineers flooded 600 acres of tribal land to build lock and dam 3. That land …