A multivariate statistical approach of overtopping probability for risk analysis at dams

flood and wind-induced high water behind a dam are two of the possible geophysical events causing its overtopping. in this paper a procedure is laid out for the evaluation of the overtopping probability due to flood and wind events. currently in austria spillway flood capacity is designed to accommodate some fixed flood, such as the once in 5000 year event for dams. The design flood itself is defined as the peak runoff. No other variables, such as the reservoir storage volume or wave heights are considered. Additionally other parameters of the design event (e.g. Time to peak, total flood volume) are assumed to be suitable. Dissatisfaction with this approach has prompted an investigation of a probabilistic approach taking account of all the other important variables, such as initial reservoir storage, wind induced wave height, outlet valve and gate openings. A research project has the aim to develop a new probabilistic design concept for spillways of dams with consideration of the reservoir management. The proposed design concept is able to optimise both safety and economy. A practicable design software has been developed to estimate hydraulic-hydrologic failure situations by means of the monte carlo method of risk analysis. The development and the practical application of the proposed method is carried out in the context of a case study concerning a reservoir of a hydro power plant in austria.