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The U.S. Geological Survey’s Grand Canyon Monitoring and Research Center (GCMRC), in coordination with the Glen Canyon Dam Adaptive Management Program (GCDAMP), has monitored the geomorphic condition of select archaeological sites along the Colorado River in Grand Canyon using high-resolution terrestrial light detection and ranging (lidar) topographic surveys.

Many of these sites are vulnerable to degradation by natural erosional processes. These monitoring data describe geomorphic effects related to the operations of Glen Canyon Dam and natural processes that influence cultural resource conditions.

Regulation of the Colorado River by some operations of Glen Canyon Dam has been shown to affect archaeological resources by directly or indirectly causing degradation of site condition.

However, some specific operations of Glen Canyon Dam, such as controlled flood releases (high flow experiments), can potentially be used to slow or stop erosion at some degraded archaeological sites.

Results of monitoring conducted with terrestrial lidar surveys from 2006 to 2010 have been synthesized in previous reports and publications.

This report summarizes the results of monitoring conducted at 30 archaeological sites within 23 monitoring locations from 2010 to 2020, presenting a sample of a much larger population of Colorado River archaeological sites in Grand Canyon that are being qualitatively monitored by the National Park Service (NPS).

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To ensure relevance to the NPS monitoring program, the quantitative high-resolution topographic monitoring presented in this report focused on sites grouped by geomorphic characteristics to identify important changes in within archaeological sites that can be related to operations of Glen Canyon Dam.

We found that 22 archaeological sites changed within one or both of the previously determined geomorphic classifications, and changes at 21 of those 22 sites were interpreted as a transition to a more degraded geomorphic condition.

The monitoring records contained within this report represent the foundation for future monitoring of these and other archaeological sites with high-resolution topographic surveys and change detection. 

These monitoring results provide benchmarks for managers of cultural resources along the Colorado River in Grand Canyon to assess significant changes to cultural resource integrity, aid in future risk management at these locations, and illustrate methods relevant for assessing geomorphic condition changes within other river valleys.

Read the report: 

Caster, J., Sankey, J.B., Fairley, H., and Kasprak, A., 2022, Terrestrial lidar monitoring of the effects of Glen Canyon Dam operations on the geomorphic condition of archaeological sites in Grand Canyon National Park, 2010–2020: U.S. Geological Survey Open-File Report 2022–1097, 100 p., https://doi.org/10.3133/ofr20221097

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