The "High Water Horns" located at the old campground/day-use only parking now that is located just before the concrete bridge at Craig Creek Rd turn off. It better be pretty loud if they expect people to hear it all the way to the gorge section.
In the last few years this has become one of my favorite MTBing parking spots. It is the first place I ever camped in this area. I think it was 1995 and I had my first kayak, a Perception Dancer. That first trip was quite a learning experience.