埋め立てに伴う潮汐・潮流の減少とそれが物質分布に及ぼす影響

Abstract

In Bays of Tokyo and Ise it is clearly shown that the emplitude and the phase lag of tide have gradually decreased for several decades. This is attributed to the remarkable reclamation of long standing in the respective bays, because the period of proper oscillation in the bay becomes smaller on account of the reduction of bay area and the response of bay water is weakened to the incidental tidal wave from the open sea. In Bay of Osaka, however, the rate of decrease of tide is rather small, because the semi-diurnal tide is low to be comparable to the diurnal tide and the tide is also influenced by the Seto Inland Sea. As for the tidal components, the decrease of amplitude is conspicuous in case of the semi-diurnal tide more than in case of the diurnal tide, corresponding to a difference between the period of them. The decrease of tidal amplitude follows the decrease of tidl current naturally, and the lowering of water exchange is inevitably anticipated between the bay and the outer sea. Then we discussed the effect of reclamation on the distribution of material based on simple theoretical considerations.