The Triesting is a river of Lower Austria, in the southeastern part of the Vienna Woods.

It discharges into the smaller Schwechat at Achau and is part of the catchment area of the River Danube.

The narrow neck of the valley above Pottenstein was blocked by driftwood and the Fahrafeld Basin turned into a dammed lake.

The dam broke and floodwaters up to 2 metres high surged through the valley.

In the whole valley 188 people lost their lives, "the majority being foreign workers".