Not sure if any property on the clack is not owned (Public or Private it would still be owned by someone). Going by the high water mark (which the river isn't considered navigable officially) you'd have about 5 feet of shore to camp on. Fires wouldn't be exactly legal either. And I wouldn't reccomend camping anywhere on the Sandy for the same reason. I know several property owners who would run you off. That said I camped many many nights along the Clack as a kid in the summer. Rode our bikes down the hill and set up anywhere we wanted or rafted to spots. But then that was before the Peoples Republic of Portland ruled over the land and people thought with their heads instead of wallets and selfishness. You'd probably get away with it, and I wouldn't tell. But then I talk on my cell when I drive, drinking a PBR, smoking a joint with a craigslist "massuse" on my lap as I bump over suicidal bicylists who think it's a good idea to ride the river rd.