The influence of canopy disturbances on landslide susceptibility in mountain forests

The Bannwald Hallstatt in the Upper Austrian Salzkammergut, is one of the oldest measures to protect the people, the settlement area, the energy supply of the community Hallstatt, as well as important infrastructure facilities in the region. In particular, the Hallstatt World Cultural Heritage Site with its settlements and access roads, which is strongly influenced by tourism, is protected.

A new project planned for 2020 will extend the area of the Bannwald forest, which has existed since 1879, in a south-westerly direction, thus protecting the permanent settlement area of the Echerntal Valley from gravitational natural hazards. As a result, the project area, which currently covers 270 hectares, will almost double to 489 hectares. 20 million euros have been budgeted for the implementation of the project, for the next 30 years. In order to be able to use these funds in an optimal and targeted manner, it is extremely important to know the protection performance of the existing forest. In the present study a model was developed to show the protective effect against rockfall and avalanches. For this purpose, an evaluation matrix with differently weighted influencing variables was developed, which was presented as a thematic map in the form of a traffic light system ("ideal"/green, "minimal"/orange, "not fulfilled"/red.). In order to be able to better illustrate the tendencies of the achieved protection effect, a “protective-forestometer” was developed. This visualizes the protection performance of the observed partial area with a pointer and a percentage indication.

However, the aim of this work was to derive the protective performance of the individual forest areas from a purely economically oriented forest management system. Hence, the data basis for this work was the 2017 forest inventory of the Austrian Federal Forestry Company (Österreichische Bundesforste AG).