Effects of DEM Resolution and Area Thresholds on Automated Fluvial Morphometry, Arroyo del Oro (Argentina)

The resolution of Digital Elevation Models (DEM) as well as the area threshold to define streams and catchments are important sources of uncertainty in automated fluvial morphometry. This study examines the applicability of three global surface models, produced with resolutions of 12.5 (ALOS), 30 and 90 m (SRTM), along with five area thresholds ranging from 0.15 to 10%. It aims at evaluating the effects of varying resolution-threshold combinations on the extraction of morphometric parameters and indices (PIm) in the Arroyo del Oro, a mountain basin located in south-western Buenos Aires (Argentina). The analysis considers the accuracy of drainage definitions, the variability of resulting PIm, and its implications for flood and water erosion assessments. Results show that the higher thresholds affect the PIm that depend on the complexity of the drainage network. Coarser resolutions impact on relief, slope and length parameters, but yield small discrepancies for the remaining PIm. For the 0.15% threshold, SRTM30 provides good fit of drainage composition parameters, and it is therefore suitable to assess the efficiency and capacity of the basin to evacuate floods. However, the use of higher resolution (ALOS12) is most suitable to assess erosion potential, due to better fit of slope-dependent PIm. Applications based on the global characteristics of middle to large-sized basins rely on a more flexible choice, as geometry parameters are unaffected by resolution and threshold.