PHYSICAL PROCESSES THAT CONTROL THE DEVELOPMENT OF THE GREAT SAND DUNES AEOLIAN SYSTEM, COLORADO, USA AND THEIR ROLE IN THE MANAGEMENT OF GREAT SAND DUNES NATIONAL PARK

Great Sand Dunes, Colorado is a geographic wonderland with varied aeolian deposits that respond to modern processes and critical land management issues generated by the desire to protect natural processes. Great Sand Dunes is the site of an aeolian system that transitions along a topographic gradient from a sabkha, to a sandsheet, to a dunefield, and ends in sand ramps juxtaposition to fault block mountains. Dune types also vary along that gradient. The variation in sand deposits and dune types result from the interaction of 5 geologic processes that are fundamental to the development of the aeolian system. These processes are: crustal rifting, sand transport related to wind regime, sand transport by stream flow, sand stabilization by vegetation growth and sand cementation by evaporite minerals. Rifting creates a depositional environment that allows sand to accumulate. Wind regime controls dune type and behavior. Streams modify the perimeter of the dunefield. Vegetation has stabilized surfaces. Other areas have been hardened by evaporite minerals.

The U.S. National Park Service (NPS) has managed Great Sand Dunes since 1932. For much of that time, the primary management focus was on visitor services, but in the late 1980s, a proposed water development project adjacent to the dunes exposed the lack of scientific knowledge used in managing the area. That began an effort to better understand the area's natural system, by identifying what resources and processes were important, then conducting research and monitoring to better understand them. This led to the geologic process model described above. The NPS has used the geologic process model to interpret the dunes to visitors, evaluate potential threats, protect park resources, and to justify a boundary expansion to manage a larger portion of the aeolian system. The potential for groundwater development adjacent to the dunes was removed by the boundary expansion.