DELTAIC PROCESSES AT THE RIVER MOUTH OF THE ABASHIRI RIVER

An elongate delta similar to the Mississippi Delta can be seen at the river mouth of the Abashiri River, which flows into Lake Abashiri where the effect of waves is negligibly small so that the riverine process is dominant. Field observation was performed in order to investigate the deltaic processes of the Abashiri River. It is found that the subaquious levees are formed on both sides of the jet axis, the formation of which can be explained by the the oretical model of the inceptive topography of river mouth bars presented by the authors. It is concluded that the subaquious levees are formed under the condition of fine bedmaterial, the negligible wave effect and dense vegetation, and that the development of subaquious leveesresults in the formation of elongate deltas.