Los Angeles River: West Bank Trail is a 14.3 mile lightly trafficked out and back trail located near Los Angeles, California that features a river and is good for all skill levels. The trail is primarily used for hiking and road biking and is accessible year-round. Dogs are also able to use this trail.
This isn't a great running path. You are completely boxed in with the freeway on one side and a river on the other. Since it is a long straight path there are bicyclists racing down the path. I found the whole run kind of anxiety inducing.