Abstract
Recently, the rainfall prediction technology utilizing numerical meteorological models have been advanced remarkably. In case of extreme flood events at some of dams, preliminary discharge and/or over-cutting flood control operations which reduce outflow discharge more than regulated are executed and recognized as considerably effective flood mitigation measures. This paper studied the risk management of rainfall prediction errors required for implementing stable and reliable flood control operations. By comparing the predicted and observed rainfalls, errors of the upper limit and the lower limit are clarified and how to define acceptable error margins regarding flood control and water use are proposed. In addition, numerical simulations are executed by applying it to the past flood control records and the method of calculating the optimal operation is confirmed.
