The Schwarza is characterized in its upper reaches by undercuts, high cliffs, gravel banks, pools and deep gullies.

The lower reaches below Hirschwang an der Rax are strictly regulated as far as Schwarzau am Steinfeld.

From Loipersbach the Schwarza runs along a sinkage section (Versickerungsstrecke), where the bulk of the water seeps into the gravel surface of the Steinfeld [bar; cs; de; sh].

The river bed below the so-called "Dunkelstein Weir" in the municipality of Ternitz usually only carries water at times of snowmelt and during heavy rain.

During heavy rainfall, snowmelt and storms, the Schwarza quickly swells into a raging torrent.

In particular, the use of "artificial nests" (spawning beds are directly injected into the substrate) supports the natural supply of brown trout.