IMPACT OF SNOW-MELTING FLOOD TO DEFORMATION OF SANDBAR AS SPAWNING GROUND FOR AYU IN YONESHIRO RIVER

Abstract

The Yoneshiro river has very good and many spawning grounds for ayu. The river experiences snow-melting flood every year from begin of March to end of May. After 2006 snow-melting flood, the river form is extremely changed and the good spawning around 22km from the mouth disappear. We think that that main reason is that the duration of 2006 flood is longer than normal year. Recently, the river researcher indicate that sandbar deformation process is affected the duration time of flood with flume experimental study and theoretic analysis. In this study, the deformation process is reproduced with 2d numerical model for river bed fluctuation to investigate the deference of the duration of flood in natural river. The results of long flood shows that river bed fluctuation is larger than the short flood like normal year.