Assessing Plot Scale Variation in Snow Depth and SWE at Very Hight Resolution using Structure from Motion

In situ instrumentation or frequent manual snowpack measurements are necessary for calculating snow water equivalent (SWE) at individual sites and for basin snowpack. However, in situ sites are sparse relative to the complexity of mountainous terrain, and manual measurements can be time consuming, and are at risk of incurring inaccuracies due to human error. Furthermore, both types of measurements are discrete and require interpolation to distribute across an entire site. Presented here is a method for mapping fine-scale variations in snow depth using Structure from Motion (SfM) - a photogrammetric technique used to image an area with overlapping 2D images to create a Digital Surface Model (DSM). This SfM application has been used at the plot scale over the Atwater Study Plot in Little Cottonwood Canyon, UT through using a recreational drone (DJI Phantom 4 Pro) and a stand-alone photogrammetric processing software product (Agisoft Metashape). We present a comparison of depth and SWE variations based on SfM-obtained snow depth measurements and discrete snow density measurements for a variety of snow conditions. We compare to other measurements, including continuous snow depth and discrete snow course measurements. Snow mapping using UAV's+SfM is of interest to the snow hydrology community and water resource managers due to its ease of use and low cost.