GROWTH, DECAY AND DISAPPEARANCE PROCESSES AND RESISTANCE CHARACTERISTICS OF SAND WAVES IN THE MOUTH AREA OF THE TONE RIVER

Abstract

 The long-term growth, decay and disappearance processes of sand waves and the variations of sand waves resistances with bed variations of the Tone River mouth from 1961 to 2007 are clarified in this paper. At first, we examine characteristics of the arrangement of dunes which are seen in the downstream of the Choshi Ohashi Bridge. Next, the long-term growth, decay and disappearance processes of dunes are indicated by the variation of cross-sectional bed forms surveyed from 1961 to 2007. The variation of sand waves resistances and bed elevations during the floods in different years is evaluated by a numerical unsteady flood flow and bed variation analysis based on the observed temporal changes in water surface profiles. At last, the characteristics of the sand wave resistances in the Tone River mouth are clarified by comparing with the previous studies on sand wave resistances in alluvial rivers.