The wash begins in two forks, Big Tujunga Creek and Little Tujunga Creek. Big Tujunga Creek begins in the San Gabriel Mountains. It flows west to a reservoir called Big Tujunga Reservoir, formed by a dam at its west shore. After exiting the dam, the creek is known as "Big Tujunga Wash". Little Tujunga Creek flows south from a portion of the San Gabriel Mountains north of the Hansen Reservoir. The combined waters then head into the Hansen Reservoir. Downstream, the Tujunga Wash flows south and halfway to the Los Angeles River, is met by the Pacoima Wash. Tujunga Wash meets the Los Angeles River near Studio City, California.