I rewatched Freaky Friday recently and was thinking that exact same thing. I assume it's some Los Angeles location it was easy for studios to get permits for.
shareThey use the L.A. Reservoir a lot in movies, this is another one.
shareI looked up Los Angeles River on wikipedia, it says: "Numerous films, television programs, music videos, and video games have featured various sites along the Los Angeles River. Since the River is a trickle for much of the year and the culvert is dry, it is often used for races, car chases, gang rumbles, and other scenes requiring an open, deserted setting within the city." Another movie filmed there was Terminator 2: Judgement Day.
share