EFFECT OF DOWNSTREAM RIVER TOPOGRAPHY ON WATER DISTRIBUTION AT THE CONFLUENCE OF ARAKAWA ESTUARY

Abstract

 To investigate the effect of the downstream river topography on water distribution at the confluence of Arakawa River estuary, a 3D flow simulator was applied. The simulator was confirmed to reproduce measured data of water level, salinity, and cross-sectional velocity at the confluence during spring tide. The results showed that the flow ratio of the Arakawa and Sumida Rivers was not proportional to the cross-sectional area ratio, which was affected by the water level difference before and after the confluence. Specifically, during low tide, the inflow from Shingashi River suppressed the diversion from Arakawa River to the Sumida River. In addition, the rapid contraction of the river width and the meandering shape of the river downstream raise the water level, which causes the distribution of water level differences at the confluence.