Abstract
Human activity has profoundly affected rivers and streams in recent Japan. Because of rapid socio-economical development in past one hundred years, patterns of land untilization has changed especially high-developed regions where flood control works has been vigorously executed. As a result of use of large scale longitudinal embankments as flood control measures, the flood flow became on a huge scale in major rivers.
In addition, in accordance with development of urbanization during these ten or fifteen years, the runoff coefficient of storm rainfall in a river basin to river course increase due to the rapid change of paddy fields and forests along the river into residential areas as well as traffic routes pavement. As a result, floods in urbanized area has an increasing tendency.
