At the Sepulveda Basin, however, more than three miles of the river are all but undisturbed, allowing the growth of willows, reeds and other vegetation and giving us a glimpse of the natural river. The Sepulveda Basin is a dry reservoir, a 2.25-square mile emergency flood-control feature behind a 57-foot earthen dam. Although much of this basin is used for recreation, with soccer, baseball, and playing fields, where the soft bottom channel of the river flows, mulefat, sagebrush, willow, and reeds cover the banks. Tributaries joining the river in the Basin are Bull Creek, Hayevnhurst Creek and Haskell Creek. Along Haskell Creek is a 225-acre Wildlife Reserve that serves as protected habitat for hundreds of species. From the Sepulveda Basin, the river flows as a concrete box channel east through the San Fernando Valley.
Big Tujunga Wash drains the northwestern San Gabriel Mountains. Starting high in the Angeles National Forest and running wild until it encounters Hansen Dam in Sun Valley, it then becomes a concrete box channel. As it continues through the eastern San Fernando Valley, it joins with the Pacoima Wash, then meets the Los Angeles River at the CBS studios in Studio City. As the river continues east past the studios, it is joined by the Burbank Wash and the Verdugo Wash in Glendale.