RIVER MOUTH CLOSURE AND WATER LEVEL VARIATION IN THE MONOBE RIVER

摘要

On-off shore sediment transport and water level variation were investigated in rivers characterized by frequent river mouth closure. Seasonal variation in on-offshore sediment transport was estimated by using the Sunamura's formula and it was found that onshore sediment transport becomes dominant in winter, and then sedimentation increases. It was considered that this seasonal change in sediment transport is caused by seasonal changes in wave period. The response characteristics of river water level to tide level change with the degree of a river mouth closure. The tide range ratio defined as the difference in the water-level of the river relative to the tidal difference is almost less than 0.5 when river mouth closure occurs.