WLS-Report 89: Riskanalysis und Risikmanagement Kienberggraben/Hassbach, on behalf of the Forest Technical Service¿s local authority Vienna, Lower Austria and Burgenland

The Haßbach torrent, with a catchment area of approx. 30 km¿, flows into its receiving stream, the Pitten river, in the municipality of Warth (district Neunkirchen). With flood events the Haßbach torrent overboarded repeated and flooded the valley area. Settlement areas, traffic areas and agricultural agriculturally productive lands were affected by it. The natural retention area is constantly reduced by increasing settlement pressure, whereby an increased protection of the habitats of the population from natural hazards is required through what. The limited available funds for protective measures have to be used after ecological and economic criteria. This requires a thorough analysis of the costs and benefits of measures to be set. The event of the summer 1999, caused by heavy rainfall in the lower catchment area, and that in June 2002, caused by heavy rainfall in the upper catchment area, led to numerous damages. These have been inundation of the valley bottom, debris surges and deposition in the muzzle areas as well as erosion in the contibutary creeks. In the already available study (WLS report 54) above all the reach downward the village Haßbach has been traeted. The upstream reach of the catchment area shall be examined in an entire study now, too. A suitable decision base shall be provided for future measures, both protection water structural and in the field of regional planning. From this a general protection concept can be derived, which represents an important component of the risk management which can be developed. The damage events of the last years serve as a basis for it.