Hydrological study for the design of retention basins at the Wartschenbach-Catchment in Eastern Tyrol.

Report19 In summer 1997 two mudflow events, which caused great damages in the Wartschensiedlung (Nußdorf-Debant, Lienz) happend in the Wartschenbach/Osttirol. To reduce the mobilisation of bed load in the middle part of the torrent, flood-retarding basins on the Zettersfeld have been picked up in the measure concept. In the frame work of this project these basins should be dimensioned. The general purpose of the project is: To set up a hydrological modell for the whole area of the Wartschenbach. To set up a detailed hydrological modell for the Zettersfeld in consideration of the single catchment areas and the sprinkler irrigation (FBVA). The determination of relevant hydrological coefficients for the flood-retarding basins A constructive and hydraulically dimensioning of the bottom outlet and the flood relief. Neighter measured precipitation nor runoff results could be used to generate a hydrological model of the Wartschenbach. To achieve plausible values the model-simulations had to be done with different basic data. Also the runoff behavior of the two events in summer 1997 was recalculated using, for the first time in the WLV history, data from a weather radar. Comparing the results with normal precipitation measurements (Ombrographen) the usability of such data should be verified. By different programms and formulae a simulation of the runoff have been done in order to ensure better results of the calculations. Surveyings, which had been done immediately after the events were used as calibration parameters. Addionally the results of the sprinkler irrigation of the FBVA have been integrated in the simulations. The flood-retarding basins have been designed as a ¿Trogsperre¿ with a rack on the waterside.