No abstract

The large-scale stationary trough system that dominated Central Europe in 2012, 2013 and 2014 led to high precipitation sums in Salzburg, Tyrol and Bavaria. In the Pinzgau and Pongau regions of Salzburg, some meteorological stations registered in June 2013 the highest precipitation sums ever recorded. In the framework of event documentation and analysis, these events were analyzed in accordance with current best practice standards and state of the art technology. The positive trend towards ever denser networks of measurement stations enables an improved quantitative capturing of precipitation and discharge data, which in turn provides an increasingly comprehensive database which can be used as input for precipitation-discharge models. With the aid of this extensive database, the measured precipitation-discharge relationships for alpine (torrent) catchment areas were recalculated, using the methodology commonly employed (HEC-HMS with the SCS method), with the ultimate aim of gaining useful insights for improved measurement practice. For this study, four catchments with available water gauges and precipitation data were selected. The calculated discharge return periods ranged from HQ2 to HQ50-100. For the Schmittenbach, an already existing model could be used; for the Urslau, an event analysis from 2002 and for the Strobler Weissenbach an event analysis from 2014 provided the required input data. The load diagram of the investigated events was derived from a combination of weather radar analyses (the spatial distribution of precipitation) and precipitation values measured at individual stations (determination of precipitation intensities).

Numeric hydraulic simulation models are used successfully in the range of flood documentation and event analysis. By using these documentations, with the help of event data sets (precipitation, discharge data, water marks...), it is possible to calibrate the provided models and to gain useful knowledge of the pros and cons and their application. In addition to that, with laser scan data sets, wide land models with a high resolution can be built and used as a basis for numerical hydraulic simulations.In the existing project, the revision of the hazard mapping Donnersbachwald resulted in the use of a numeric hydraulic simulation as a supplement to the common methods (historic method, literature-investigation, analysis of previous planning and expert opinion).For the project "Delimitation of hazard zones at the torrent Donnersbach/Styria" two-dimensional and one-dimensional hydraulic simulation models were used in addition to the common planning methods (historical method, literature search, evaluation of past planning and appraisals).Different scenarios were calculated, varying the input hydrograph (the hydrologic calculations were carried out with the aid of the HEC-HMS model), flooding process and blockage of bridges. The selected sections lie in the valley at the bottom of the community of Donnersbach with a slope angle of between two and five percent.After evaluation of existing data sets with the help of historical event data in principle, two questions for the simulation resulted:1. The effect of blockage of existing bridges for the overland flow. 2. Retardation of flow due to the storage effect of overland flow for the main stream in Donnersbach. With the two-dimensional numerical simulation the reciprocal effects of the subordinated processes and different discharge scenarios could be considered and analyzed. The results were used on one hand as a support instrument for the delineation of hazard zones and on the other hand as documentation material for the public work.