Photo: BMLFUW/Hopi Media
Protection against natural hazards
Forests protect us against floods, mudflow, avalanches, slope movements, and rock fall. These natural hazards threaten Austria’s residential and economic areas as well as its traffic routes.
Being also a mountainous country Alpine natural hazards constitute a security risk in many of Austria’s regions. With three quarters of its total federal territory Austria has the highest percentage share of Alpine land of all Central European countries. More than half of Austria’s national territory (83,855 km²) are intensive zones of protection against alpine natural hazards.In the course of the past few decades the increasing settlement pressure, the opening up of transport routes in the Alps as well as massive growth rates in tourism (skiing areas in high alpine regions) have brought about a considerable spatial extension of the endangered areas.
But also flat residential areas which extend to wetlands as a result of the settlement pressure are flood-prone. Wetlands are potentially at risk of being flooded by the rivers and brooks draining the Alps. This does not only concern the Danube region, but also intra-Alpine rivers and brooks.
Floods develop from extreme precipitation, which, in the catchments of brooks and rivers, leads to a rapid rise in the run-off and, consequently, to inundations in the valleys.
At www.hochwasserrisiko.at it is possible to get a first assessment of the flooding risk along rivers by entering the relevant address. This project, flood risk zoning in Austria (HORA), is a cooperation of the Ministry of Life and Versicherungsverband Österreich, the association of Austrian insurance companies.
The excessive burden on torrents with stones, gravel, mud (bedload), and wood (woody debris) causes mudflow. Mudflows may sweep away and destroy individual houses, but also entire villages.
Bare rock, which, due to the natural vegetation patterns, is predominantly found in high-alpine locations, is particularly prone to erosion, for example rock fall or debris avalanches. However, due to climate change, air pollution and lack of protection forest rock fall may occur in lower zones, too.
Avalanches constitute a great danger in winter and during the snow-melting period. They threaten not only winter athletes and the entire infrastructure established for the winter tourism. Rather, they may endanger entire intra-Alpine villages and traffic routes.
As a protection against all these natural hazards, forests are established and tended. The trees of the protection forests stabilise the alpine soil with their roots and take up moisture from the soil. Water is extracted from the soil, mudflow is prevented.
Every tree constitutes a solid barrier against avalanches and rock fall, due to and in accordance with its size and incorporation in the terrain. In Austria’s protection forests sub-alpine spruce forests, mountainous spruce-fir-beech forests, dwarf-pine areas, and larch-stone pine forests are dominant.
Since the amendment of the Forest Act in 2002 protection forests have not only been classified in site-protecting forests and protective forests (‘Bannwald’); there is also the additional category of object-protecting forests. Whereas site-protecting forests protect their sites, which means: themselves, object-protecting forests are forests which protect humans, human settlements or facilities or cultivated soil against natural hazards and injuring environmental impacts.
According to the Austrian Forest Inventory 2000/2002 776,000 hectares, or approximately 20 percent, of the forested land, are to be considered protection forest. Of this 20 percent share, 8 percent are protection forest with yield and 12 percent are non-productive protection forest. Half of the protection forest area with yield shows absence of natural regeneration; in non-productive protection forests one fifth of the – necessary - natural regeneration is missing.
There are too few young plants to take over the protective function once the existing trees have become too old to fulfil this function. There are many factors that prevent or disturb regeneration: Browsing by game, forest pasturing, overgrowing with grass, erosion, but also lack of light due to excessively dense canopies.
The protection against alpine natural hazards is one of the responsibilities of the Forest Engineering Service in Torrent and Avalanche Control, an agency of the Ministry of Life. Experts analyse and assess hazards by means of Hazard Zone Plans, plan and carry out protection measures such as torrent control and avalanche fences. There are over 12,200 torrent catchment areas and about 6,000 avalanche catchment areas in Austria.
30.06.2008, Lebensministerium Öffentlichkeitsarbeit