Green Drake nymphs are burrowers. They come out of the silt and are active before the duns hatch. Often, the trout gorge on the nymphs which leave them indifferent to the emerging duns. The spinnerfall of the glowing white coffin flies are an event worth seeing also. About an hour before dark, find a riffle on Abrams and look up into the sky. You may see a gathering cloud of the coffin flies that will slowly get closer and closer to the water. eventually, with just about a half hour of light remaining, they will start dropping to the surface, laying eggs and/or dying. If you are positioned downstream of the drop-zone, the action could be heavy. Trout seem to really like food that can't get away.
Please bear in mind that I have no idea what I am talking about.