The Koritnica River springs from several tributaries and mountain streams from below Mangrt, Kotovo sedlo and Jalovec.

The upper part mostly sinks in the sandbanks and at the village it flows to the riverbed again, which passes to troughs immediately after the village of Log pod Mangrtom (at the turning of the road towards the Možnica Valley) and continues to the next deepest troughs (70-80 m) in Slovenia.
Those can be viewed from the bridge at the Kluže Fortress.

The river continues its way through smaller basins below the fortress, and then along the riverbed until it joins the Soča River (at Vodenca).

The right tributaries are:
- Ilovec,
- Predelica,
- Roja,
- Nemčlja,

and the left are:
- Kaluder,
- Fratarica,
- Šumnik, which flows from the Bavšica Valley.

The other tributaries have the character of mountain streams.