SUSTAINING ARCHAEOLOGICAL SITES IN A SEDIMENT-DEPRIVED ECOSYSTEM: DESIGNING A MONITORING PROGRAM TO ASSESS GLEN CANYON DAM EFFECTS ON DOWNSTREAM ARCHAEOLOGICAL RESOURCES IN GLEN AND GRAND CANYONS, ARIZONA

In 1963, construction of Glen Canyon Dam on the Colorado River was completed, profoundly altering the downstream riverine ecosystem in Grand Canyon National Park. One consequence of the dam’s emplacement and subsequent operation has been a greater than 85% reduction in the amount of fluvial sediment entering Grand Canyon. The paucity of sediment to re-supply sand bars and replenish sand dunes along the river shoreline has not only altered the bio-physical dynamics of the riverine ecosystem but has also affected the physical settings and geomorphologic stability of numerous archaeological sites located in the river corridor downstream of the dam. For the past decade, US Geological Survey scientists have been exploring various tools and methods to accurately capture the effects of ongoing dam operations on downstream archaeological resources. We are now in the process of implementing a comprehensive monitoring plan based on an ecosystem framework that incorporates diverse measurements and classification procedures to objectively assess how current dam operations impact the physical integrity of archaeological sites. Our approach incorporates measurements of topographic change using repeat high-resolution lidar surveys, plus measurements of sediment flux, vegetation growth, local meteorological conditions, and other parameters to help land managers understand how dam operations affect archaeological sites and inform future management and mitigation strategies.