MONITORING MOVEMENT OF ACTIVE SAND DUNES WITHIN GREAT SAND DUNES NATIONAL PARK AND PRESERVE

We used a Trimble GeoXH handheld differential global positioning system unit to monitor the displacement of several active sand dune crests located adjacent to and on the main dune mass of the Great Sand Dunes National Park and Preserve in south-central Colorado. This equipment provides positional information with a horizontal accuracy of 5 to 15 cm for >95% of the points during a survey. Previous studies used aerial photography to document the movement of parabolic sand dunes outside of the park boundary. Here we report dune movement along the southern edge of the main dune field, close to the area most heavily used by the public when climbing the sand dunes. The dunes we monitored included one whose crest is constantly walked on by hikers going to and from the dune parking area, as well as several dunes less frequently traversed by visitors. There is considerable variability of dune crest location on an annual basis, even along a single dune. For example, portions of the crest of one dune (oriented WNW-ESE) moved >9 m NNE annually over the period from 2014 to 2017, while a N-S-oriented crest on the same dune (within 50 m of the movement just cited) moved annually 0 to 5 m E (and even 3 m W) during the same survey period. A nearby dune displayed a similar NNE overall movement while also showing the growth of an E-W-oriented ‘arm’ that likely indicates the initiation of a new star dune. When compared to local wind records, dune orientation clearly affects how a dune responds to the dominant wind pattern. These initial results indicate that the micro-topography associated with a steadily shifting array of dune forms can lead to a surprisingly complex movement pattern across a large sand accumulation.