MITIGATION EFFECT OF PADDY FIELD DAM ON INUNDATION DAMAGE IN SUKAGAWA-CITY: CASE OF TYPHOON HAGIBIS, 2019

We investigated the mitigation effect of ”Paddy field dam” on inundation damage due to Typhoon Hagibis, 2019 in the Sasadaira River catchment where “Paddy field dam project” is implemented by Sukagawa city office. The inundation area was estimated from the measured river water level and the digital elevation map. The water storage of paddy field was calculated from the database of paddy shape delineated with areal photogrammetry with UAV. The results illustrated that the estimated water storage in the paddy fields in the upstream area decreased the inundation area by 50% and the inundation volume by 25% at the maximum flooded condition. It implies that paddy fields have a supplementary effect to mitigate inundation damage by working as a stormwater storage facility in the small river catchment even under heavy rain which exceeds design rainfall.