Lake Lanier (officially Lake Sidney Lanier) is a reservoir in the northern portion of the U.S. state of Georgia. It was created by the completion of Buford Dam on the Chattahoochee River in 1956, and is also fed by the waters of the Chestatee River. The lake encompasses 38,000 acres or 59 square miles of water, and 692 miles of shoreline at normal level, a "full summer pool" of 1,071 feet above mean sea level. It was named for poet Sidney Lanier, and was built and is operated by the U.S. Army Corps of Engineers. It is patrolled by the Georgia Department of Natural Resources (GDNR). The lake is in Hall, Forsyth, Dawson, Gwinnett, and Lumpkin counties, split about 60%, 30%, 5%, 4%, and 1% respectively, filling the valley into numerous small arms and fingers. The former thalweg of the Chestatee and the Chattahoochee south of it form the county line between Hall and a tiny corner of Gwinnett to the east, and Dawson and Forsyth to the west. One of the main purposes of the lake is flood control downstream of the lake, mainly protecting metro Atlanta. There have only been two major flooding events on the downstream section since the construction of Buford Dam. The most recent flooding event was in 2009.