Changing Rapids in Grand Canyon: Granite Rapid

I have always thought of granite rapid as a big sleigh ride. You crest the top, ride some enormous, stationary rollers, and then suddenly what seemed to be a frozen slope turns very wet and lands in your face. To most river runners still boating in Grand Canyon, Granite Rapid represents a relatively confined entry at the top right and then a move to the left, with goals of staying off the right wall and staying out of what some boaters call Forever Eddy on the lower right. It s a big ride with a high probability of flipping for smaller oar boats.
John Wesley Powell seems to have been fascinated with Granite Rapid. He had his photographer, Jolly Jack Hillers, take three photographs of the rapid in 1872, which means Hillers took more photographs here than any other place on the river except the mouth of the Little Colorado. Powell featured a drawing of his boats running what he called Granite Falls in his fictionalized account of his first river trip in 1869. The problem is that Powell only ran rapids when his men couldn't portage easily, such as at Sockdolager Powell definitely portaged Granite (see accompanying photographs). Bill Belknap made the drawing well known by featuring it on the cover his river guide.
Later river runners photographed the rapid as well. Stanton took three photographs of the river in 1890. Raymond Cogswell took seven photos of the rapid in November 1909. The Kolb brothers attempted to match Hillers upstream view along the edge of the rapid in December 1911. By the middle of the 20th century, photographs were regularly taken. One of the reasons is that the rapid was regularly lined and the photographers had a lot of time on their hands. One of the first women to go through Grand Canyon, Lois Jotter Cutter commented on how boring it was to walk around all the rapids in 1938. In 1994, on her second trip, she was quite happy to be riding in a boat instead of walking around Granite Rapid.
Granite has changed considerably since 1872. My information comes from matching 15 historical photographs of the rapid and examining another dozen aerial views or photos that couldn't be matched easily. Also, I've been observing this rapid closely since 1984. Probably the most striking change is the reduction in the size of the sand bars at the foot of the rapid. Once one of the best beaches in terms of size in the Inner Gorge, these sand bars have been reduced to almost unusable to river runners now. The beach on the left above the rapid is a pale shadow of its former self and at times resembles a mud wallow.
But the rapid itself has changed several times, and some of the changes were rather dramatic. The rapid that Powell and Stanton saw was wide with a shallow, rocky left side. Hal Stephens matched two of Hillers' photographs in 1968. In one from high above the river, a debris flow issuing from Monument Creek has clearly changed the upper part of the debris fan (Webb and others, 1988, 1989). We narrowed down the year of this debris flow to between March 1967 and September 1968 (Melis and others, 1994). This one was small but the first indication of what was to come.

A debris flow on July 25, 1984, caused major changes in Granite Rapid. The debris flow, which started at a large avalanche in the headwaters of Monument Creek, covered most of the debris fan and entered the rapid. Two distinctive holes on the upper left were eliminated by boulders. Brad Dimock was there on July 27, and the debris flow was still oozing and calf deep in places. He had to run a rogue wave that he hadn't seen before or since in the rapid, and a photograph shows the wave towering about 6 feet above his dory. My first river trip in Grand Canyon took me to Granite Rapid in early August 1984. I remember walking on the by-then hardened surface of the debris fan, seeing my first definite proof that debris flows did indeed occur in Grand Canyon. The 1984 debris flow increased the fall through the rapid and increased its speed, leading to the rapid that most of today's river runners know so well.
Much of the 1984 debris-flow deposit was washed downstream towards the island during the high water years between 1984 and 1986. The rapid became stable for a decade, until the flood in March and April, 1996, moved some three to six foot boulders around on the edge of the debris fan. Another debris flow, on July 15, 1996, added a lot of relatively small boulders to the surface of the debris fan, but few of the boulders entered the river at its typical dam-controlled levels except above the rapid, where a splay of cobbles and boulders entered the upper pool. This deposit may have helped slow the erosion of the upper beach. Now, when you walk over the surface of the debris fan, the 1996 deposit is what is most apparent. Monument Creek is a frequent producer of debris flows, one of the most frequent producers in Grand Canyon. Expect to see more changes in the sleigh ride, probably in the near future.
Bob Webb

Melis, T.S., Webb, R.H., Griffiths, P.G, and Wise, T.J., 1994, Magnitude and frequency data for historic debris flows in Grand Canyon National Park and vicinity, Arizona: U.S. Geological Survey Water Resources Investigations Report 94-4214, 285 p.
Webb, R.H., Pringle, P.T., Reneau, S.L., and Rink, G.R., 1988, The 1984 Monument Creek debris flow: Implications for the formation of rapids on the Colorado River in Grand Canyon National Park: Geology, v. 16, p. 50–54.