FRZA – Flood Risk Zoning Austria, 2004-2005 (HORA)

Federal Government Department for Agriculture and Forestry, Environment and Water Management
TU Vienna, Institute for Water Engineering and Engineerhydrology, Univ. Prof. Dipl.Ing. Dr. techn. Günter Blöschl

The main objective of the project “Flood Risk Zoning Austria (FRZA)” was the recording of flood areas for flood water flows HQT of the annualities T=3, T=100, and T=200, referring to the on the scale of 1:500 000 registered Austrian water network (ÖK 500) with a total length of ca. 26 000 km.

The evaluation of the flood areas is divided in a hydrologic and a hydraulic part.Die

Together with the TU Vienna we took the work package Hydrology.
The goal of the hydrologic part was the determination of the flood water flows HQT which served as input parameters for the hydraulic part of the project.
FRZA is all about an estimation of the flood risk, so the identified flood water flows were defined as estimations for the most probable data for a destined annuality. It is common practice that rated values of the rate of flow cover uncertainties. These rated values are sometimes – depending on the extent of the uncertainty – picked bigger than the most probable data. Because of that, the FZRA-data may differ from discharge rated values.

A 2-part method was chosen:

  • Determination of the flood water flows HQT for surveyed catchment areas (discharge levels) in the whole of Austria in accordance with the individual federal authorities.
  • Regionalisation, while considering catchment area parameter – i.e. determining of the flood water flows HQT for unsurveyed areas.

The findings of the hydrologic part have been laminary pictured by means of the hydraulic development.
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