Drone–based camera discharge derived from the entropy–based probability concept and image velocimetry algorithms

In June and August 2023, the U.S. Geological Survey (USGS) conducted small Uncrewed Aircraft System (sUAS or drone) flights at five streamgages in the Upper Colorado River Basin, Colorado, USA. The objectives of this research were (1) compare maximum surface velocities and discharges derived from Space-time Image Velocimetry (STIV) and Particle Image Velocimetry (PIV) and (2) evaluate drone-based camera algorithms that rely on the entropy-based probability concept and mid-section method relative to standard discharge measurements.
To evaluate the scalability and transferability of the methods, river reaches were selected with varying top widths, depths, and discharges and colocated with existing USGS streamgages. Percent errors between drone-based camera algorithms and hydroacoustic measurements were substantially smaller for large rivers such as the Colorado River, Colorado when compared to small rivers such as the Blue River, Colorado. A Wilcoxon signed-rank test suggests there was no difference between the discharges generated by STIV and PIV algorithms and hydroacoustic measurements. This implies that, if the appropriate algorithms are properly parameterized, drone-based camera discharges are consistent with standard discharge measurements when siting is conducted appropriately.