APPLICATION OF RGB AND MULTISPECTRAL DRONE (SUAS) PHOTOGRAMMETRY OF ALLUVIAL FANS IN THE GRAND VALLEY OF COLORADO USA FOR DETECTING SHALLOWLY-BURIED CHANNEL FEATURES THAT MAY ACT AS GROUNDWATER CONDUITS

Paleochannels in alluvial fans are known to be potentially important high-permeability groundwater conduits in semi-arid climates. In these systems, identification of paleochannels is critical in both clean and contaminated water studies. Sites in and around the Grand Valley along the Western Slope of Colorado, USA, represent the leading edge of this kind of water-related research in high altitude semi-arid environments, due to the ongoing water-resource concerns in the Upper Colorado River Basin and potential point sources of groundwater contamination entering the basin via throughflow/shallow groundwater flow. The objective of this study is to assess detection of shallowly-buried alluvial fan paleochannels at a test site near Grand Junction, Colorado, associated with potentially critical water flow. Data include: (i) high-resolution RGB & multispectral photogrammetric maps of the test site, (ii) three-dimensional structure-from-motion (SFM) models of the test site in RGB and multispectral, and (iii) geological maps along the edges of the target alluvial fan site where modern valleys expose cross-sections of paleochannels (used for control). The results of this project—particularly the advances in multispectral orthophotogrammetry—may be applicable to similar sites in similar areas, as well as possibly expanded to other climates and elevations with similar shallowly-buried groundwater pathways.