THE HISTORY AND GROWTH OF A RECENT DUNE FIELD AT GRAND FALLS, NAVAJO NATION, NE ARIZONA

The formation of dunes and dune fields is not commonly observed and is a poorly understood aspect of aeolian science. Dune fields can be built by one or more (geologically) rapid constructional events such as a sudden influx of sediment, changes in wind transport capacity, or changes in aridity. Current work to document the genesis, growth, and migration of dunes in northeastern Arizona consists of an array of techniques that we are applying primarily at a dune field near Grand Falls, north of the Little Colorado River. These include historic georeferenced aerial photos, high precision GPS measurements, ground based LIDAR, meteorological monitoring, Landsat Imagery, field sampling, and the history of flood events and stream flow of the adjacent Little Colorado River. These techniques allow us to assemble the story of dune growth and migration on the downwind side (north east) of the Little Colorado River, and the record of control that ephemeral alluvial processes have had on local dune activity. The Grand Falls dune field formed from circa 1940 flood deposits. The dune field continues to grow as dunes migrate downwind at rates as high as 34 m/yr. Ongoing studies will quantify how ephemeral stream flow, flood events, and climate variability and change are reflected in dune field morphology and growth.