WhiteboxTools

WhiteboxTools, from John Lindsay's Geomorphometry and Hydrogeomatics lab at the University of Guelph, packs over five hundred geoprocessing tools into a single fast Rust binary — and its hydrological terrain analysis is the deepest available anywhere: depression breaching (its least-cost breaching is the reference implementation), flow pointers and accumulation in many flavours, stream extraction, wetness indices and lidar processing.

It runs standalone, from Python, or inside QGIS/ArcGIS via frontends, with no dependencies to install. For DEM conditioning and delineation pipelines, WhiteboxTools is usually the sharpest free tool in the drawer.