Study on a flood damage reduction countermeasure by installing a spillway on a riverine levee for promoting the initiative of River Basin Disaster Resilience and Sustainability by All

Abstract. In light of the frequent occurrence of unprecedented heavy rains and floods attributable to climate change effects, the importance of the “River Basin Disaster Resilience and Sustainability by All” initiative is being emphasized and promoted strongly in Japan. For promoting discussions on a wide range of countermeasures for flood damage reduction by the initiative, this paper presents a trial estimation result of quantitative flood damage reduction effect by spillway installation on a riverine levee in a protected area where severe flood disasters have occurred in recent years. The result shows that the countermeasure considerably reduce the flooded area, the days required for drainage, and house flood depths. Results also indicate that the average annual damage to paddy fields in the area can be expected to decrease, although the inundation frequency will increase.