 Vista Ridge, a small plateau, is in the southeast corner of Lewisville, and the lowest part of Denton County, at , is found in the city.Lewisville sits above the Barnett Shale, a geological formation containing a large quantity of natural shale gas.Water constitutes of the city's total area, including Lewisville Lake, the Elm Fork of the Trinity River, and two local tributaries of the Elm Fork, Prairie Creek and Timber Creek.