Surecatch-

Buffer zones are based on stream type/width, sight potential tree height and basal area along with a couple other factors that play a lesser role. The 50 feet that you heard represents the core zone which is a "no touch" zone, with a couple of exceptions involving roads. Outside of the core is the "inner zone" and then there's the "outer zone". Some management (ie harvest) may take place in the inner and outer zones depending on existing basal area. There are essentially two options that a landowner may choose from. In western washington, the total buffer zone on fish bearing streams can be anywhere from 90-200 feet in width. It's different on the eastside and I don't remember what they are. Buffers are also required on non fish bearing streams, but their is a table that would be difficult to reproduce here that is used to determine the extent of the buffer.