1979 aerial view of Mission Bay, Ocean Beach, and bay and river channels. The San Diego river has changed its course several times. In the late 18th century it emptied into False Bay, the present day Mission Bay. In the 1820s it altered course and emptied into San Diego Bay, which continued for nearly 50 years. The river was diverted to its present course in 1877 by a dam and the straightening of the channel to the ocean.