An analysis of the current stability of the Dune Field at Great Sand Dunes National Monument using temporal TM imagery (1984–1998)

Research conducted at the Great Sand Dunes National Monument (37°46.5′N, 105°32.5′W) thus far has focused on dune composition in order to explain formation, dune migration to monitor aeolian processes, and dune extent to detect encroachment in the eastern periphery, a region that contains several visitor services. These studies used a series of field techniques in conjunction with aerial photography; however, modern satellite data, such as temporal TM imagery, were not used to track changes of the dunes. In this study, I used two TM images from 1984 and 1998 to examine changes in dune extent. A series of image enhancements, including edge enhancements were applied, and a supervised classification was conducted. Overall classification accuracies, based on ground truth data, ranged from 89% (1998) to 91% (1984). Over the study period, the amount of sand in the entire complex decreased in area by 416.4 ha, dune grass decreased by 487.5 ha, and a semidesert scrub category containing a mixture of bushes, taller grasses, and desert pavement increased by 1457.3 ha. Few changes in the extent and orientation of the main dune complex were observed; however, notable changes were observed in the periphery. On the western side of the complex, dune grass is slowly being converted to scrub; as a result, the extent of exposed sand is decreasing. On the eastern side, dune grass and scrub are increasing, succeeding upon the dunes. These results demonstrate the stability of the main dune complex and suggest that dune migration in the periphery is no longer a concern.