The optimal DEM resolution for determining sediment connectivity at runoff plot scale

Digital Elevation Model (DEM) resolution significantly influences the representation of surface topography and the assessment of sediment connectivity, which is crucial for understanding erosion processes and optimizing soil and water conservation (SWC) measures. However, the optimal DEM resolution for runoff plot sediment connectivity remains unclear, particularly in complex terrains such as the Loess Plateau. This study aimed to: (1) analyze the effects of varying DEM resolutions (2 cm to 100 cm) on sediment connectivity indices (IC) across different SWC measures and slope gradients; (2) identify the most suitable DEM resolution for sediment connectivity assessment at the runoff plot scale. Using high-resolution DEMs generated through UAV/Structure from Motion (UAV/SoFM) photogrammetry, the study encompassed 14 runoff plots (5 m×20 m) on the Loess Plateau. Results showed that IC values increased with coarser DEM resolution but stabilized beyond 20–30 cm, indicating the resolution-dependent nature of IC. The optimal DEM resolution varied with SWC measures: 20 cm for woodland with fish-scale pits, grassland under contour cultivation, and control plots without SWC, and 30 cm for farmland with horizontal ridging. Additionally, significant differences in IC values (P < 0.05) were observed among SWC measures, with control plots exhibiting the highest IC value (-2.18), indicating greater connectivity, while farmland under horizontal ridging exhibited the lowest IC (-3.20). These findings underscore the importance of selecting the appropriate DEM resolution for accurate sediment connectivity assessment and optimizing SWC measures to mitigate erosion. The results provide valuable insights for sediment connectivity evaluations at the runoff plot scale globally.