Los Angeles River

The Los Angeles River (Spanish: Río de Los Ángeles), historically known as Paayme Paxaayt 'West River' by the Tongva and the Río Porciúncula 'Porciúncula River' by the Spanish, is a major river in Los Angeles County, California. Its headwaters are in the Simi Hills and Santa Susana Mountains, and it flows nearly 51 miles (82 km) from Canoga Park through the San Fernando Valley, downtown Los Angeles, and the Gateway Cities to its mouth in Long Beach, where it flows into San Pedro Bay. While the river was once free-flowing and frequently flooding, forming alluvial flood plains along its banks, it currently flows through a concrete channel on a fixed course, which was built after a series of devastating floods in the early 20th century.

Before the opening of the Los Angeles Aqueduct, the river was the primary source of fresh water for the city. Although the Los Angeles region still receives some water from the river and other local sources, most of the water supply flows from several aqueducts serving the area. The Los Angeles River is heavily polluted from agricultural and urban runoff.

Fed primarily by rainwater and snowmelt (in winter and spring), the Donald C. Tillman Water Reclamation Plant in Van Nuys (in summer and fall), and urban discharge, it is one of the few low-elevation perennial rivers in Southern California. Some water usually reaches the ocean, even in the driest summers; although there are historical accounts of the river running dry, there has been constant flow of the river every month since recording of stream flow began in 1929. This is helped by the concrete channel, which limits absorption of water into the earth. Flow, while generally low in volume, can be extremely brisk even in summer.

The Los Angeles River's official beginning is at the confluence of two channelized streams – Bell Creek and Arroyo Calabasas – in the Canoga Park section of the city of Los Angeles, just east of California State Route 27 (Topanga Canyon Boulevard), at 34°11′43″N 118°36′07″W / 34.1952°N 118.601838°W / 34.1952; -118.601838 (the east side of Canoga Park High School). Bell Creek flows east from the Simi Hills, and Arroyo Calabasas flows north from the Santa Monica Mountains. From there the river flows east through a concrete flood control channel and very soon receives Browns Canyon Wash, which flows south from the Santa Susana Mountains. The river then bends slightly south and receives Aliso Canyon Wash, whose watershed adjoins that of Browns Canyon. The river then flows through the district of Winnetka, then Reseda and enters the Sepulveda Basin, a flood-control reservoir formed by the Sepulveda Dam.

As the river proceeds into the usually-dry reservoir, it spills out into a channel that is similar to its historical, non-channeled form. It crosses under Balboa Boulevard and then receives Bull Creek. The river then passes through the outlet works of Sepulveda Dam, 43 miles (69 km) from the mouth. It flows again into a concrete channel and crosses under the San Diego (405) Freeway as it passes through Van Nuys, Sherman Oaks, and Studio City, still flowing east. Paralleling U.S. Highway 101 briefly, it then veers southeast, away from the highway, and receives from the left the Tujunga Wash, one of its largest tributaries, which flows southwest and south from the Angeles National Forest in the San Gabriel Mountains. The river then rounds a bend to the northeast, now in a concrete box culvert, and crosses under the Hollywood (170) Freeway and Highway 101, and receives Burbank Western Channel on the left bank, 39 miles (63 km) from the mouth.

The river then begins to parallel the Ventura (134) Freeway as it winds through North Hollywood and the city of Burbank. It then crosses under the Golden State (5) Freeway and makes a sharp bend to the south-southeast as it curves around Griffith Park. It receives from the left Verdugo Wash, which drains much of La Cañada Flintridge and Glendale as it flows from the San Gabriel Mountains south through a water gap in the Verdugo Mountains, and crosses under the Ventura Freeway. Here, the river begins to flow over a natural riverbed, but enters another concrete section soon after. Paralleling the Golden State Freeway for the next few miles, the river runs by the eastern side of Griffith Park and the Harding-Wilson Golf Course. It passes Silver Lake Reservoir, which is to the right, and crosses under the Glendale (2) Freeway, 32 miles (51 km) from the mouth.

Making two meanders as it flows in a southeasterly direction, the river parallels the interstate and Riverside Drive then crosses under the interstate and Arroyo Seco (110) Parkway as it flows east of Elysian Park. It then receives the Arroyo Seco, another major tributary, from the left. The river flows south past the Mission Junction, a large railroad yard on the left. It enters a wider concrete channel with sloped sides, and crosses under Cesar Chavez Avenue, the Hollywood (101) Freeway, and the San Bernardino (10) Freeway as it passes east of downtown Los Angeles, flowing past the East Los Angeles Interchange of the Santa Ana (101) Freeway, Pomona (60) Freeway, and Interstates 5 and 10 on the left. It then makes a gradual turn east and then turns southeast, flowing a few miles before it begins to parallel the Long Beach (710) Freeway near Maywood, Bell, Cudahy, and Commerce, 20 miles (32 km) from the mouth.

Paralleling the Long Beach Freeway south-southwest, the river then crosses under former California State Route 42 and the interstate as it receives the Rio Hondo from the left, 9 miles (14 km) from the mouth. The Rio Hondo ("deep river") now serves as a distributary for the San Gabriel River to the east via the Whittier Narrows Reservoir. The river then crosses under the Century (105) Freeway and shifts slightly southwest, then flows east of Compton and west of Bellflower. After crossing under the Artesia (91) Freeway, it receives Compton Creek from the right, 2.7 miles (4.3 km) from the mouth. After crossing under Interstate 405 for the second time, 2 miles (3.2 km) from the mouth, it draws close to the Dominguez Channel to the west and flows due south to its outlet in Long Beach, under Interstate 710, past the RMS Queen Mary, and into the Port of Long Beach.