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The majority of archaeological sites in the Grand Canyon National Park, Colorado River corridor were created by ancestors of Native Americans who still live in this region, including Havasupai, Hopi, Hualapai, Navajo, Southern Paiute, and Zuni. These sites record indigenous peoples’ presence and history in the national park. 

Along the Colorado River in Grand Canyon National Park, windblown river sand provides important wildlife habitat, sandy areas for camping, and a protective cover for archeological sites. The potential for archaeological sites to be buried, and thus protected, by wind-deposited river sand has decreased since construction of the upstream Glen Canyon Dam in 1963, and the proportion of sites eroding by gullying processes has increased, making most sites more erosion-prone now than they were when the dam was first constructed. These erosional processes in turn cause sites to be more exposed to additional potentially negative impacts from weathering from rain and wind, as well as human visitors. Erosion of sites is contrary to the management goal of the National Park Service to maintain or improve sites in place as cultural resources in the park.  

Photographs of different types of erosion that physically degrade archaeological sites along the Colorado River, Grand Canyon
Photographs of different types of erosion that physically degrade archaeological sites along the Colorado River in Grand Canyon National Park:  All photos by Jennifer Dierker, National Park Service, used with permission. 
Photograph of an archaeological site threatened by gully erosion of sediment on a river terrace in Grand Canyon National Park
A partially-buried archaeological site in Grand Canyon National Park threatened by gully erosion of sediment on a river terrace near the Colorado River. Photo by Helen Fairley, USGS.

Despite the past erosion, river management opportunities could help reduce the increased risk of erosion to sites in the future. In new research recently published, the USGS evaluated the effectiveness of management experiments that are being conducted by the Bureau of Reclamation and National Park Service, through the Glen Canyon Dam Adaptive Management program.  

One river management tool for increasing windblown sand is to release artificial “floods” (termed controlled floods or high flow experiments) from the dam to deposit sand above the level of typical river flows so it can be redistributed by wind and deposited on sites.  

An alternative approach is to lower river flows and expose sand that is usually underwater, allowing it to dry sufficiently to be moved by wind; this is currently relevant as Colorado River managers are facing water shortage conditions, and less water in the river will likely result in more frequent lower flows, allowing more wind transport of sand for maintaining sandy landscapes throughout the river corridor.  

A third alternative is to remove invasive riparian vegetation on river sandbars which otherwise blocks the wind from blowing sand on top of sites to keep them buried and protected. 

Native peoples have inhabited the Grand Canyon region intermittently for at least 10,000 years. European explorers first visited the canyon 480 years ago. Today, people primarily visit the area to appreciate the natural and cultural resources and to recreate. Evidence of the prehistoric occupants and of more recent historic activities is reflected in hundreds of known archaeological sites within the riparian corridor of the Colorado River in Grand Canyon National Park, which spans about 224 river miles (360 kilometers) of the 246,000 square miles (637,000 km2) Colorado River basin. 

Before/after veg management photographs of a sand dune adjacent to a Colorado River sandbar
Photographs of a windblown (aeolian) dune in Grand Canyon National Park adjacent to a Colorado river sandbar before (inset) and after vegetation removal conducted by the National Park Service, which is intended to increase aeolian sand transport inland from the river, toward the right side of the photograph. This area is near an archaeological site. Photo by Joel Sankey, USGS.

Many of the archaeological sites are situated on or in river flood deposits and sand dunes formed from sediment derived from the Colorado River. Prehistoric and historic Native American sites include masonry dwellings, storage structures, ditches, trails, agricultural fields, seasonal campsites, petroglyphs and pictographs, roasting pits, and quarries. The oldest sites in the river corridor date to the Archaic period, which began roughly 9000 years ago, though older sites occur elsewhere in Grand Canyon. However, most river corridor sites are associated with Ancestral Puebloan people and date between 750 and 1250 CE. Other sites date more recently to Pai and Paiute occupation beginning at approximately 1300 CE and continuing into the EuroAmerican historical era. Examples of the area's  historical era sites include remains of cabins, ferry boat and river crossing infrastructure, mining locations, and cowboy camps dating from the 1860s–1950s. 

To learn more about this research: 

Archaeological sites in Grand Canyon National Park along the Colorado River are eroding owing to six decades of Glen Canyon Dam operations:  

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