IMAGERY DERIVED FROM SMALL UNCREWED AERIAL SYSTEMS USED FOR STAGE-DISCHARGE MODELLING OF EPHEMERAL CHANNELS ALONG THE SAN JUAN RIVER NEAR THE FOUR CORNERS REGION OF THE SOUTHWESTERN UNITED STATES

Streamflow data are required to calculate loads of constituents, such as metals. In locations such as ephemeral channels, where direct measurements of streamflow are inconvenient, cost prohibitive, or impossible to obtain, streamflow can be computed from stage information when paired with a stage-discharge rating. Digital terrain models can be used to model streamflow at various water depths, resulting in a model derived stage-discharge rating for specific stream locations. However, obtaining the terrain data necessary to develop a stage-discharge rating can be time intensive and cost prohibitive. Recent developments in photogrammetry, combined with low-cost uncrewed-aerial systems (UAS), have created new approaches to generating high-fidelity terrain models using low-cost digital cameras deployed on small UAS. This approach is being used to quantify streamflow in approximately 35 ephemeral channels near the San Juan River from Navajo Dam to Mexican Hat. Preliminary results of these streamflow modelling efforts will be presented.