Abstract
Field observation of flood damages caused by heavy rainfall associated with Typhoon 9719 occurred on September 16, 1997 was carried out along the Yasaka River in Oita Prefecture as well as aerial photographing of inundated areas. In this flood, maximum discharge of around 1, 500m3/s, which exceeds planned flood discharge of 1, 250m3/s of this river, was measured. Inundation height was measured at 66 points and relation between distribution of submerged houses and morphology around the river was studied. The direction of flood flow was read from the falling direction of paddy field and deposition of sand was observed behind dense bamboo forest due to the roughness effect of the forest. Aerial photographs show that flood flow went straight while causing inundation and scouring just behind the dike at meandering areas.
