Are you aware of any organization that offers regular tours of the L.A. River?

If you’re interested in walking parts of the nearly 50-mile-long, concrete-lined, often dry waterway, you can do it several times a year with Friends of the Los Angeles River, a nonprofit group dedicated to restoring and protecting it. The fee is typically in the $20 to $30 range. In addition, Urban Photo Adventures, a company operated by movie location scouts, will resume its own political-sociological-economic-religious-architectural tours in September. The outings, which cost $249, take ten hours on each of two days. Excursions are limited to 15 participants, who go by bus, boat, and on foot. As movie scouts, the tour guides have entree to parts of the river that are not accessible to the general public.
Photograph courtesy Flickr/amayzun