REGIONAL EVALUATION OF POTENTIAL FLOOD DAMAGE REDUCTION BY PADDY FIELD DAM IN JAPAN

Abstract

 This study estimated the potential flood damage reduction effect by a paddy field dam throughout Japan. The inundation depth caused by flooding was calculated using a two-dimensional unsteady flow model. The flood damage cost was calculated by multiplying the asset value of the inundated land by the damage rate based on the inundation depth. A simple paddy field dam model, which could be applied to a wide area, was applied to whole Japan to reflect the rainwater storage function of the paddy field dam in the flood inundation analysis. If paddy fields throughout Japan were used for flood mitigation, flood damage cost was estimated to decrease by 6.5 %. The flood damage cost reduction rate due to the paddy field dam was the highest in Toyama prefecture, followed by Saga prefecture, Akita prefecture, Yamagata prefecture and Niigata prefecture. The comparison between the previous study and this study showed that reduction ratio of the flood damage cost by the paddy field dam was lower than that by land-use control, piloti building and improvement of flood-control level.