Courtesy of The Los Angeles River Center

rom the mountains to the city to the ocean, the Los Angeles River winds through Los Angeles County for 51 miles crossing 13 cities. Although a majority of the river is lined with concrete, there are still sections with sandy bottoms where water nourishes lush vegetation, ducks feed and nest, and migratory birds take a rest along its riverbanks.

The Los Angeles River is the heart of an 871-square mile watershed. The watershed encompasses the Santa Monica Mountains to the north and west, the San Gabriel Mountains to the north and east, and the Los Angeles coastal plain to the south, and ends at the Long Beach Harbor. The Los Angeles River, in 51 miles, drops in elevation 795 feet, and the watershed, in 40 miles, drops over 7,000 feet from its highest point to the estuary in Long Beach. Bell Creek and Calabasas Creek flow from the Santa Susana Mountains into the Los Angeles River beginning at the headwaters in Canoga Park.

Water that does not percolate into the ground flows down to the Los Angeles River and into the San Fernando Valley. Some of this water is returned to the water table when it reaches the Sepulveda Basin and other dry reservoirs. From the Sepulveda Basin the river flows east through the San Fernando Valley joining with the Tujunga wash near Studio City and with the Verdugo wash in Glendale. Past Griffith Park, as the river runs south from what is known as the Glendale Narrows, the river flow along the naturalized riverbed portion of the river referred to as the Elysian Valley. Below the Elysian Valley is the confluence of the Arroyo Seco and the Los Angeles River.

The Arroyo Seco drains the southwestern section of the San Gabriel Mountains. The Arroyo Seco starts high in the San Gabriel Mountains and runs through Pasadena near the Rose Bowl, continuing through South Pasadena to the confluence. Here the Los Angeles River becomes fully concrete and is spanned by architecturally interesting bridges. Few using the bridges realize they are crossing the Los Angeles River.

To preserve these bridges, the riverbed was lowered and piers of the bridges enhanced and strengthened so that the river could be clad in concrete. Further downstream the Rio Hondo joins the Los Angeles River from the east. The last tributary mingling with the Los Angeles River in Compton Creek. South of Compton, the river flows down between a concrete or rock channel into the estuary in Long Beach.

As urbanization fills the hills and valley, less water seeps into the earth. Concrete, roofs, and asphalt create runoff, which is sent directly into storm drains, and from there, into the Los Angeles River. This paving of the watershed taxes the carrying capacity of the river, since most of this water would have been absorbed into the water table and not diverted to runoff.