Transition of grasses and management of river dike

Evaluation of protective function of grasses covering a river bank against erosion due to flood flow is important for grasses to be used for the protective measures instead of concrete armoured bank. On the real river, however, transition of grasses takes place and the preffered kind of grasses may change from the turf being planted at the construction time. Thus the understanding of transition process is very important in such an evaluation of protective function of grasses. This study aims to investigate this transition process of grasses through a field observation in the Iwai River in Iwate Prefecture. Annual change in covarage rate of grasses was observed at river banks of various stages after the construction.