Most of the impressive rocks of the Gesäuse consist of Dachstein limestone, which in many cases sits on a bedrock of Dolomite. This carbonate rock is predominant in particular in the west of the National Park, where it forms an impressive "erosion landscape" characterised by deep and gravel-filled gullies, distinctive rock towers and pierced rock.
Dolomite weathers relatively easily, producing large amounts of scree. In the event of flooding, this debris is transported to the Johnsbach and Enns by the rapidly swelling torrents or is deposited along or within the stream bed.
These gravelly torrent beds are characteristic features of the Dolomite erosion landscape. The erosion material provides the basis for the unique habitats of the Gesäuse in particular in the form of dried out gravel-filled gullies (e.g. Langgries, Weissenbachl) and gravel bars along the banks of the Johnsbach and Enns. The flood control measures taken in the past century have led to a significant reduction of these habitats in Central Europe.
Langgries is a prominent example of a huge gravel stream descending from the Dolomite rocks of the Admont Reichenstein. An estimated 10,000 m³ of scree is produced by weathering and transported downslope as far down as the Johnsbach and Enns. It clearly illustrates the dynamic processes of deposition and terracing on the one hand and erosion and transport on the other.
A concept has been developed to protect existing infrastructure by allowing natural processes to occur, while also ensuring the protection of roads and bridges. The necessary strategies and responsibilities have been defined in the management plan.