The river widens and turns south around Griffith Park, and heads through what is known as the Glendale Narrows - a rocky bottleneck that forces any underground water to the surface to join the visible river. Here begins the soft-bottom portion of the river referred to as the Elysian Valley, another eight miles of river lush with islands of trees, brush and reeds, and a favorite haunt of birds on the Pacific Flyway. 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. Starting high in the San Gabriel Mountains and running through Pasadena near the Rose Bowl, it continues through South Pasadena to meet the LA River just north of Downtown Los Angeles.
After the confluence the Los Angeles River becomes a fully concrete trapezoid channel and is spanned by architecturally historic bridges that carry automobiles full of people - who rarely 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!