ast year, instrument stations were set up by the US Geological Survey and National Park Service to monitor eolian (wind-blown) sediment transport at several locations along the river corridor (see bqr Vol. 17, No. 1). Data from these sites has so far proved very useful in helping to predict how changes in dam operations might affect areas where archaeological sites are threatened by erosion.
Here are the highlights from this project, from data recorded over the past year…
During the “windy season” of April–May, measured rates of eolian sand transport were up to ten times higher than during other times of year. The strongest winds then (and greatest sand transport) tend to blow upstream, as many of you have probably realized while trying to row downstream during these spring winds! The highest wind velocity that we recorded was 66 miles per hour, on July 16th, 2004 near Forster Canyon. Several other days in April and May came close to that in areas of Marble Canyon, but that 66 mph was the winner. Our 2004 record for rainfall in a single event recorded within the canyon was set on the night of September 18–19 as a dissipating Pacific storm system (Hurricane Javier) passed over Grand Canyon… more than two inches of rainfall were measured in some areas, causing flash floods and blowing out arroyos. I have to admit, the scientific merit of this impressive storm was temporarily lost on me that night as I got up at 4 a.m. to move my tent away from the flooding creek at Cremation.

Following the November flood experiment, we now have a valuable opportunity to use these same instrument stations to study how wind re-distributes the new flood-deposited sediment. All of the instrument sites experienced major new sand deposition as a result of the November flood flow. As we enter the windy season this spring, we’ll be able to determine how the post-flood sand-transport rates compare with those measured last year, and to document where that sand ends up; in some locations, the new flood deposits are expected to supply new sand to eolian dunes up above the river, helping to preserve archaeological sites. Data collected at these stations can therefore help us understand how, and where, the November flood (and any future floods) will be most beneficial for archaeological resources.
Instrument stations used for this study are permitted through Fall 2005, at which time they are scheduled to be removed. If you come across any of these instruments while on a river trip, please ensure that your group respects them—they are used to help us understand how to preserve and manage valuable cultural resources. And many, many thanks for your help with this over the past year—we’re really excited about the progress of this work!

Amy Draut
US Geological Survey