Los Angeles River Headwaters: Simi Hills at 1,924 Feet

Where the Concrete River Begins

The Los Angeles River originates in the Simi Hills at the Santa Susana Mountain Pass—a low saddle between the Simi Hills and Santa Susana Mountains in the northwestern San Fernando Valley.

Precise Location

• Coordinates: 34.195° N, 118.601° W (approx.)
• Elevation: ~587 m (1,924 ft) above sea level.
• Confluence: Bell Creek + Calabasas Creek = official LA River start.
• Landmarks: Near Canoga Park High School; west of Topanga Canyon Blvd.

From Mountain to Channel

• Upper 15 km: Natural, intermittent stream; riparian corridor.
• Sepulveda Basin: Flood control reservoir (1941); wildlife reserve.
• Channelized reach (1938–60): 60+ km concrete trapezoid.
• Revitalization zones: Glendale Narrows (soft bottom), Taylor Yard, Piggyback Yard, Lower LA River.

Watershed Context

• Basin area: 2,170 km² (834 mi²).
• Length: 82 km (51 mi) to San Pedro Bay.
• Tributaries: Arroyo Seco, Rio Hondo, Compton Creek, Tujunga Wash, Verdugo Wash.
• Management: LA County Flood Control District + Army Corps + City of LA + NGOs (FoLAR).