The Development of Sand Waves and the Maintenance of Navigation Channels in the Bisanseto Sea

Abstract

An Inosakinotsugai is a shoal located in the Bisanseto navigation channel, on which are formed sand waves of 100m wavelength. The heights of sand waves develop to be about 5 meters, which makes the water, depth shallower than that required for navigation. Authors have analyzed the process of sand wave development by utilizing the sounding data obtained during a period from 1984 to 1996. As a result, it is shown that 1) the sand waves developed faster in the area where the speed of sand accumulation is faster, 2) the sand waves migrated from the both sides of the shoal toward the shoal ridge, and 3) the speed of migration is proportional to the horizontal distance from the ridge. In the maintenance dredging, the developing speed of sand waves must be taken into consideration.