OBSERVATIONS ON DUNE BEHAVIOR AT GREAT SAND DUNES NATIONAL PARK, COLORADO

Great Sand Dunes is located in southern Colorado’s San Luis Valley and it is believed to contain the tallest dunes in North America. It is an aeolian system that includes a sabkha, sandsheet, dunefield, and sand ramps. The aeolian features, along with the rugged Sangre de Cristo Mountains create a scenic landscape that is managed by the National Park Service (NPS). Understanding the behavior and development of the Great Sand Dunes is important to the NPS as it strives to preserve and protect them.

A variety of dune types have developed at Great Sand Dunes in response to changes in wind regime and variability in available sand supply. NPS staff has been using GPS mapping, aerial imagery, traditional surveying methods, and meteorological data to document dune migration, growth, and correlate dune migration to wind regime. Twenty index dunes have been chosen to track dune movement within the GRSA aeolian system. In 2011 the dunes were mapped by LiDAR at 1 laser return per meter, when repeated, LiDAR measurements are made in the future, this would provide a means to analyze dune movement though-out the aeolian system.

This talk will focus on 4 index dune sites that characterize dune migration for their area. Some are small, migratory dunes typical of unimodal wind regimes. Others are large, vertically growing dunes common in areas with bi-modal or complex wind regimes. Monitoring the dunes has giving insight to how migration varies based on dune size, how dunes merge into one a single form, and a possible mechanism for vertical dune growth and that will be presented as well. Additionally, a new explanation for the origin “escape dunes” is also proposed based on the dune migration findings. The escape dunes are small dunes east of the main dunefield that were believed to have escaped the main dunefield during a drought in the 1950s.