|Sediment release and transport associated with the Arase dam removal, first challenge of dam removal in Japan, were investigated and its properties were compared with pioneering dam removal cases in United States. In the first year when the crest of Arase dam was removed, about 26% of trapped sediment (mainly sand and gravel, including cobble size stones) in the former reservoir was washed away, forming new sandbars and channels at the downstream. However, the sediment release sharply decreased in the second year (>3% of total) despite the large amount of sediment still remaining. Rocks constituting a rapid before the dam construction appeared along with sediment runoff and affected the resistance. In terms of suspended sediment, the significant impacts were not identified. A comparison of dam removal properties showed that sediment size in the Arase Dam removal was larger than those in the US cases, although hydraulic capacities of sediment transport in floods did not differ significantly. The gaps between sediment size and actual transportability affect both sediment release rate and recovery from the dam removal impact on downstream.