A STUDY ON THE VEGETATION EXPANSION AND TOPOGRAPHICAL CHANGE AT DOWNSTEAM REACH OF THE TENRYU RIVER

Abstract

In the present study, the topographical change and the expansion of riparian vegetation were investigated at the downstream reach of the Tenryu river, where the decrease of sediment supply due to dam construction and the resulting vegetation expansion were observed. It was found that the increase of the flood plain width during 1970 to 1980 induced the change of sandbar form from multiple bar to alternative bar, which stabilized the main channel of the river. Whereas the vegetation area tend to increase in recent years, the immigration and the destruction of the vegetation have still been active, and the renewal of the riparian vegetation is very high at the downstream reach of the Tenryu river.