Gschliefgraben/Gmde. Gmunden: Preparation of historical data sources as a basis for future mitigation measures
Abstract
On 28.11.2007, about 2 million m³ of accumulated solids were triggered by an earth flow of the torrential catchment “Gschliefgraben”, which is located in Upper Austria, on the banks of the lake “Traunsee”. Dislocation velocity was up to 4.7 m/24 hours and as a result the mass of earth threatened to damage not only numerous buildings (37 estates with 55 buildings) but even to shift parts of the settlement, located on the sliding mass, into the lake, as the “Gschliefgraben” did in past centuries. Deposition height at the fan was up to 8 m. Already 300 years ago the activity of the “Gschliefgraben” was well known and resulted in a sub aquatic fan, 900 m wide and 120 m deep. The hazard map of this region (1987) delineated a wide red hazard zone and since then no more buildings were raised there, even though the location is in great demand. However, not only the adjoining buildings, but moreover all infrastructure facilities are threatened by landslides (rural roads, water-, electrical- and communication routes), supplying the “Unterm Stein” district, which is accessible only via this road. Implementing immediate measures required complete removal of the vegetation on the site of activity to drain the water from the slope, having in view the hazard potential of the sliding mass. However, from a medium-to-long-term perspective, a holistic approach for mitigation strategies was undertaken to protect the “Gschliefgraben” and all the elements at risk. In particular, drainage structures can permanently decrease the instability of the masses of earth. Moreover, a combination of soil bio-engineering and forestal measures, as well as torrential structures made of timber and stones will be put in place. As public interest is prevailing, mitigation measures will largely be funded from public expenditures (~80%), by the affected municipality (~10%) and by infrastructure companies and the occupant of the forests (~10%). Half a year later (May 2008), the masses of earth are still in motion.
keywords earth flow hydrology GIS
Publikationen
Project staff
Johannes Hübl
Univ.Prof. Dipl.-Ing. Dr.nat.techn. Johannes Hübl
johannes.huebl@boku.ac.at
Tel: +43 1 47654-87111
Project Leader
01.10.2008 - 01.09.2009