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Code of Practice for the Assessment of Surface Runoff Coefficients

Runoff in the mountain region

The first BFW “Code of Practice for the Assessment of Surface Runoff Coefficients for Alpine Soil/Vegetation Complexes in Torrential Rain” has been published in 2004 (in German language). The Interreg-South East Europe-Project CC-WaterS offered the opportunity to integrate some new findings in experimental runoff research and to release a report in English language in 2011. This report has found great interest by practitioners and scientists since.

The first simple “Code of Practice for assessment of surface runoff coefficients in convective torrential rain (version 1.0)” was presented in 2004. It was based on the results of rain simulation experiments utilising a transportable spray irrigation installation for the assessment of runoff behaviour on typical runoff contributing areas in alpine catchments.

These experiments had been carried out at the Department of Natural Hazards of the BFW in Austria and the LfU in Bavaria for more than three decades. These investigations usually have been combined with investigations on site characteristics, e.g. information on vegetation and soil. Data from more than 700 single rain simulation experiments have been stored in a joint database and analysed in detail.

The version 1 of the Code of Practice has evolved into a basic means for the derivation of surface runoff coefficient maps, which are needed to calculate peak runoff and runoff amount in torrent catchment areas in case of extreme precipitation, e.g. the recurrent design event.
Within the last years target-oriented spray irrigation experiments have been continued and new insights into runoff development have been gained:

  • The Federal Ministery of Agriculture and Forestry, Environment and Water Management funded investigations about runoff development in long duration rain events.
  • The Austrian Academy of Sciences (ÖAW), Commission of Hydrology, has granted money for research dealing with the theme “Assessment of bandwidths of shallow interflow velocities in alpine catchments”.
  • Additional results from simulations of torrential rain have been earned in work for BFW-projects and in the frame of orders by the Austrian Avalanche and Torrent Control Service (WLV).

This information and data have been combined with the results of the investigations in the Interreg SEE-project CC-WaterS (Climate Change and Impacts on Water Supply) in Waidhofen a.d. Ybbs and been incorporated into the present version of the “Code of Practice (Version 2.0)”.


Code of Practice (Version 2.0)