Direct Observation of Sediment and Carbon Connectivity: Evaluating Degradation Pathways, Conservation Implementation and True Cost Accounting: Final Report

This final BIOAg report documents UAV-based photogrammetry used to observe winter-season erosion dynamics and sediment connectivity at a primary Palouse field site during water year 2021. Eight missions (November–April) produced dense point clouds and DEMs to evaluate rill initiation, rill-to-gully development, and surface change across key periods around a major January 12, 2021 precipitation event.

Ground control point (GCP) survey error limited change-detection resolution (LOD ~56–61 mm), though analysis suggests true relative precision between missions may be higher. The study found rill formation strongly aligned with high-resolution flow accumulation patterns, with a site-year rill threshold near 250 m² contributing area at ≤1.25 m DEM resolution. Soil organic carbon analysis was halted due to COVID-related lab closures. Using Sentinel-2 NDVI as a yield proxy, the team explored spatial profitability and estimated nutrient-loss costs, highlighting the difficulty of separating erosion impacts from strong topographic controls on productivity. The report recommends prioritizing robust surface-derivative metrics (slope, flow accumulation, roughness) and expanding long-term, multi-partner monitoring to capture infrequent, high-impact events.