Vegetation in rivers causes serious problems such as increases in flood risk due to water level rise during flood. Salicaceae trees are dominant on flood plains and sand bars of rivers in cold and snowy Hokkaido. Therefore, it is crucially important to inhibit the growth of salicaceae trees for river management. While there is a problem that salicaceae trees are flourishing in the Satsunai River, one plant species in the family salicaceae, chosenia arbutifolia, is losing its habitat. Chosenia arbutifolia is registered in the red data book of Japan. Hokkaido Development Bureau, the management authority, is performing field experiments to sweep away young salicaceae, and to form fluvial bars covered with gravel by artificial flash flood with the use of snow melting water released from Satsunaigawa Dam. Authors studied the habitat situations of young salicaceae and chosenia arbutifolia before and after an artificial flash flood, and relations between hydraulic conditions and habitat of the plants.
