PHYSICAL PROCESSES THAT CONTROL THE DEVELOPMENT OF THE
GREAT SAND DUNES AEOLIAN SYSTEM, COLORADO, AND THEIR ROLE IN
THE MANAGEMENT OF GREAT SAND DUNES NATIONAL PARK.
VALDEZ, ANDREW
Great Sand Dunes National Park & Preserve, 11500 Hwy 150, Mosca, CO 81146
andrew_valdez@nps.gov
Abstract
Great Sand Dunes, Colorado 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.