2.2.1. Imagery Acquisition
We acquired basemap imagery for the digitization of the valley plug in
2021 with an unmanned aerial vehicle (UAV; DJI Mavic 2 Pro) outfitted
with a Hasselblad L1D-20c camera (20MP 1” sensor), or from available
high resolution aerial photos. For 2021 imagery collected by UAV, we
collected imagery at flight heights ranging from 300 to 350 m at 20 mph.
We post-processed imagery in DroneDeploy (dronedeloy.com) to produce 2
cm resolution orthomosaic images (e.g., Carbonneau et al. 2020; Oakland
2020). We also used historic imagery from Google Earth (June 6, 2009,
and April 2, 2015; Maxar Technologies, State of Utah, USDA/FPAC/GEO;
~0.15m resolution) to capture conditions prior to 2021
and for our reference reaches: Moonshine Wash and Spring Canyon.
We collected UAV imagery on September 23, 2021. Flows for the UAV
imagery were a maximum of 0.40 and a minimum of 0.30 cms. Historic
imagery flows were a maximum of 8.10 and a minimum of 7.14 cms for 2009,
and a maximum of 0.26 and a minimum of 0.12 cms for 2015. Flows were
measured at US Geologic Survey (USGS) gauge #09328500 San Rafael River
near Green River, Utah.