Revisiting Geomorphic Changes Caused by the Dondokosawa Rock Avalanche in the Akaishi Mountains, Central Japan

Topographic analysis using LiDAR-based geomorphological map tied up with field survey was performed to revisit geomorphic changes caused by the Dondokosawa Rock Avalanche, which scattered huge granitic rock clasts at around AD 887 along the Dondokosawa River, a branch of the Komukawa River in the Akaishi Mountains, central Japan. It is revealed that the rock avalanche completely blocked two parts, the outlet of right tributary of the Dondokosawa River and the channel reach of the Komukawa River of at least 630-m length, forming two dammed-lakes (estimated areas of 0.02 and 0.10km2, respectively) together with floodplain deposits beside the rock avalanche deposits.