According to River Runners for Wilderness (RRFW), Hance Rapid at mile marker 77.2 underwent a major change on August 25, 2012, due to a flash flood careening out of a canyon on river left.
One of the handful of difficult and legendary rapids on the Grand, where the run is rocky and the holes many, the rapid is a thirty foot drop in a little over a half mile, as measured in the 1923 USGS survey.
A series of monsoon storms in late August, however, brought massive amounts of boulders and gravel to the rapid via Red Canyon, the side canyon responsible for the debris in the river at Hance Rapid.
“Hance is a classic rapid,” says former Grand Canyon guide Steve Conlin. “This makes it completely different. I can’t wait to get down there to see it.”
The left run of Hance is often chosen by river runners to avoid large right side holes. Due to the recent flooding, the left run is now blocked by boulders and gravel. The new material has moved more of the river’s flow to the center of the river. Scouting the rapid in its new configuration is strongly advised, says RRFW.
The distinctive large room sized boulder on river left, known variously as the Muffin or Brain or Hamburger Rock, was the marker for the left run. River runners attempting this route would try entering to the left of this boulder to enter the slower water just below it.
Before the construction of Glen Canyon Dam, completed in 1963, spring snowmelt river flows well over 100,000 cubic feet per second would clear away boulders and gravel from side canyon flood events like the one in Red Canyon. Today, managed flood flows only reach 45,000 cubic feet per second, too low to flush the side canyon debris on down the Colorado River, potentially making rapids much more difficult, especially at low water
Two aerial photos of the new rapid taken August 24, 2012, have been posted at the River Runners for Wilderness photo Gallery. RRFW would like to thank Michael McComb for the use of these photos. The link to the photos can be found at http://rrfw.org/gallery/