We tied up the rafts to scout this rapid before going through. It started rain....REALLY HARD....then as we were about to get back in the rafts, the hail started...we were pummeled with rather large hail for about 10 minutes preventing us from getting in the rafts...and that is when the flash flood came out of the side canyon. Can't tell from the video, but it was probably 6-10 feet deep, 50-60 feet wide, and ran for about 1/2 hour at an amazing speed, and sounded like a freight train as it filled the left side of the river with rocks forever changing the rapid. According to the river guides, this was a once in a lifetime event to witness, especially one this large....and we were the first ones to go through the newly formed Hance rapid.