PRELIMINARY QUANTIFICATION OF SEDIMENT STORAGE IN MORAN AND AVALANCHE CANYONS IN GRAND TETON NATIONAL PARK, WYOMING, USA

The study of temporary sediment storage in incised drainages in the Teton Range is essential to for studies that want to characterize the landscape response to post-glacial climate conditions since the Pinedale Glaciation ended at ~13 ka. Here, we present the results of storage landform mapping and estimates of stored sediment volumes in the lower reaches of Moran Canyon and Avalanche Canyon in Grand Teton National Park. Best-fit curves using exposed bedrock in the valley walls along a total of 28 cross sections were used to project an estimated bedrock surface under the sediment. The curve fitting tool in MATLAB was used and a smoothing spline fit was selected interactively for each cross section. Sediment storage landforms were mapped in ArcGIS by combining aerial photos with a 0.5 meter DEM (with hillshade and slope maps) derived from LiDAR data flown in 2014. The total volume of sediment in the lower 5.7 km of Moran Canyon is approximately 0.089 km³ in an area of 5.07 km², indicating an average thickness of 19 m. 44.2% of the depositional area consists of debris fans, talus cones and talus sheets. 42% of the area consists of bedrock with a veneer of debris, 10.4% is alluvium and 3.4% is clearly exposed bedrock (a rôche moutonnée). The total volume of sediment in the lower 2.2 km of Avalanche Canyon is approximately 0.023 km³ in an area of 1.3 km², indicating an average thickness of 17 meters, and the proportions of landforms are similar to Moran Canyon. In comparison, the Pinedale-aged glacial moraine deposited at the mouth of Avalanche Canyon has a volume of 0.3 km³. Future work to constrain the estimated bedrock surface would include geophysical methods such as GPR, resistivity or seismic refraction. Detailed field mapping needs to be performed in order to better observe and understand how the glacial, periglacial, fluvial and hillslope processes interact to produce these landforms.