Author(s): Steyrer Peter
Linked Author(s):
Keywords: Free overfall jet; Stilling basin; Energy dissipation; Scour; Nature test series
Abstract: Ottenstein dam is a concrete arch dam in the Kamp valley, a northern tributary to Danube river. It was built in the fifties and is still under operation without troubles. Flood dissipation is done over a crest spillway with a free overfall water jet into a stilling basin in the tailwater. As rock conditions were expected excellent it was completely omitted to have a solid concrete apron for protection of the rock floor. During commissioning nature tests were carried out to verify the effectiveness of energy dissipation of the flood spillway. As consequence of this tests damage of the rock floor appeared with scour up to 5 m depth. Further test series and natural floods in the following years did not show any more damage after readjustment of the scour with anchored concrete plates. Interpretations were made but no explanation was found up to the nineties. As meanwhile in Austria spillways of large dams have to be improved to a peak discharge of a 5000 yearly flood by regulations of federal commission the owner of Ottenstein power plant was forced to find an explanation for the damage and a prognosis for the effect on the rock floor that would be caused by a 5000 yearly flood.
Year: 1999