2005 Volume 11 Pages 227-232
This paper describes flood protection planning in an idealized basin with non-stationary fluctuation of extreme daily rainfall frequency and proposes a method of non-stationary frequency analysis of rainfall. It is discussed that under the condition of climatic change that changes an occurrence process of rainfall, traditional frequency analysis and a method of planning that assumes stationary rainfall occurrence process could not be used. Analysis of daily rainfall frequency is developed based on non-stationary Poisson process using an annual occurrence rate and probability distribution of daily rainfall obtained from historical time series at Osaka. Amount of daily rainfall with a 100-year return period assuming non-stationary fluctuation exceeds that of a 1,000-year return period with assumed stationary frequency.
The idea of maximizing benefit within the planning duration is proposed in a basin with non-stationary fluctuation of daily rainfall frequency. As a result of applying the risk analysis to an idealized basin, river channel improvement is effective for increasing benefit and dam construction is more effective if it is done at earlier stage.
