I am not sure about that counties regs but here in King If I did similar I would be required to leave such brush in the creek. It's illegal to clear w/o a permit but I can "maintain" So chucking the brush in the creek would mean I did not clear it because it is still there.

A complaint would be with the counties land use office (same place you get a building permit)and you can do it with a phone call.
_________________________
Liberalism is a mental illness!