The Union Bay Natural Area (UBNA) in Seattle, Washington, also known as Union Bay Marsh, is the restored remainder of the filled former Union Bay and Union Bay Marsh. It is located at the east end of the main University of Washington campus, south of NE 45th Street and west of Laurelhurst. Ravenna Creek is connected to University Slough, thence to Union Bay, and Lake Washington. Drainage Canal is one of three or four areas of open water connected with Lake Washington around Union Bay Marsh. The canal extends from NE 45th Street, between the driving range and IMA Sports Field 1, south to the bay, ending southeast of the Husky Ballpark baseball grandstand. The Drainage Canal that carries Ravenna Creek past UBNA to Union Bay is locally sometimes called University Slough.