In November 2004, an experimental high flow release of water from Glen Canyon Dam into the Colorado River through Grand Canyon National Park in Arizona was conducted. The goal of the experiment was to evaluate the use of high flow events as a management tool for the preservation and restoration of natural resources in the Colorado River below Glen Canyon Dam. The U.S. Geological Survey (USGS), Grand Canyon Monitoring and Research Center (GCMRC) located in Flagstaff, Arizona performed oversight of all aspects of scientific data collection including suspended sediment transport studies, biological population variations, effects on archaeological resources, and morphological studies of river sand bars. As part of the experimental high flow studies, the USGS Coastal and Marine Geology (CMG) team was invited to participate to test the effectiveness of utilizing terrestrial LIDAR technology for gathering morphological data on sand bars, biological habitats, and archaeological sites. The CMG is equipped with a terrestrial LIDAR unit and has used the technique in a variety of terrains to gather high-resolution morphological data. A three-member team from CMG participated in the experiment, joining a GCMRC team on a river trip from November 18 to November 21, 2004. This report begins with a brief description of the LIDAR technique and then outlines the data collected, processing required, and results for three study areas located within the Grand Canyon. Specifically, studies were performed at the Mile 30 Sand Bar, at Vaseys Paradise (Mile 32), and at the Mile 66 Palisades Archaeological Site. Conclusions and recommendations for utilizing terrestrial LIDAR for future studies at each of these sites are also included.

Human occupation in Grand Canyon, Arizona, dates from at least 11,000 years before present to the modern era. For most of this period, the only evidence of human occupation in this iconic landscape is provided by archeological sites. Because of the dynamic nature of this environment, many archeological sites are subject to relatively rapid topographic change. Quantifying the extent, magnitude, and cause of such change is important for monitoring and managing these archeological sites. Such quantification is necessary to help inform the continuing debate on whether and how controlled releases from Glen Canyon Dam, located immediately upstream of Grand Canyon National Park, are affecting site erosion rates, artifact transport, and archeological resource preservation along the Colorado River in Grand Canyon. Although long-term topographic change resulting from a variety of natural processes is inherent in the Grand Canyon region, continued erosion of archeological sites threatens both the archeological resources and our future ability to study evidence of past cultural habitation. Thus, this subject is of considerable interest to National Park Service managers and other stakeholders in the Glen Canyon Dam Adaptive Management Program. Understanding the causes and effects of archeological site erosion requires a knowledge of several factors, including the location, timing, and magnitude of the changes occurring in relation to archeological resources, the rates of change, and the relative contribution of potential causes. These potential causes include sediment depletion associated with managed flows from Glen Canyon Dam, site-specific weather and overland flow patterns, visitor impacts, and long-term regional climate change.