Studies on the Blocking of the River Mouth (VI)

On the drift shores and blocking of the river mouth along the coast of Tosa bay

Abstract

The study was made in order to find out the mechanism of the blocking of the river mouth and to get materials for its improvement.
The size of shores and foreshore slopes and the diameter of drift were measured on the main drift shore of Tosa bay from Muroto to Ashizuri in Kochi prefecture. I studied geophysically the distribution of shores, its characteristics and drift transport, etc.
There is no remarkable differences geologically between the eastern and the western coasts. But the former has a larger slope a greater number of rivers, so that there is a greater quantity of drift.
Because the waves which act on th eastern coast are flatter and have more energy than those on the western coast, there is found more drift transport. Consequently, the on-shore drift are more often shown than the off-shore drift, moreover the foreshore slope and the diameter of the drift are large, which make the drift shore develop.
From such an analysis, river mouths in drift shores are classified into the deflective, straight and protective types, for each of which it became possible to decide the fundamental method of improving the river mouth.