RIVER CHANNEL CHARACTERISTICS AND THE SCALE OF NATURAL LEVEES IN LOWER REACHES

Abstract

The scale of natural levee is various, but the factor which causes the variety has not been revealed. On the other side, shape of river channel is also quite various, and the channel shape is considered to be determined by the factors that affects natural levee shape. In this research, the scale of natural levees around Kanto region is measured. Additionally, width/depth ratio of segment 2-1 is estimated and the grain size distribution of bed material is measured. It is clarified that length and width are correlated and long and wide natural levees are created in the area where the riverbed slope is mild. It is also revealed that natural levees on rivers which have quaternary volcano in the geology of basin tend to be high. Moreover, by focusing on geomorphological features, characteristics of width/depth ratio are clarified. Width/depth ratio is high in segment 2-1 where the alluvial plain is narrow among mountains or plateaus. Width/depth ratio is low in segment 2-1 and 2-2 of rivers which have Jurassic accretionary complex.