抄録
The current evaluations of flood risk are generally based on the index of very heavy and rare rainfall, such as the intensity of 100 years probability precipitation. However, this approach may lead to the underestimation of flood risk because the statistical records suggest that the flood damages can be caused by moderate rainfall events as well. Here we introduce a new method for evaluating flood risk which utilizes the distribution of daily rainfall intensity in order to include the flood damage due to the frequent rainfall into the evaluation. The precipitation intensity of each day is converted to the PEP(Precipitation Exceedence Probability) index which represents how rare the precipitation intensity of the day is compared to the probability of exceedence of the annual maximum daily precipitation. The proposed method suggests that the flood risk caused by less than 30 years probability precipitation is estimated up to 78% of the all flood risk. The proposed method seems robust because the evaluated annual flood damage all over Japan agrees to the actual flood damage recorded on the national statistics.
