Abstract
In the front sea area of Mama-river mouth which there is near the tidal flat of Funabashi Sanbanze sea side park, the radioactive cesium density was estimated quantitatively based on an observation result. In addition, a charactristic of radiation dose was analyzed in the tidal flat. As a result, a possibility of the change of the radiation dose in the tideland area was considered in the tidal flat of Funabashi Sanbanze sea side park.