WhiteboxFDFAC
Flow direction (Flow pointer) and Flow accumulation calculation using Whitebox tools in QGIS, part of watershed delineation.
The process is some variation of
1) Condition DEM through a Breach or Fill,
2) Flow direction (also known as Flow pointer),
3) Flow Accumulation,
4) Identify high flow areas near watershed outlet location (typically through symbology settings or a Reclass operation,
5) Create/snap pour points,
6) Watershed calculation