抄録
The River Takahashi, which flow through the west side of the Kurashiki city in Okayama Prefecture, had naturally brought about, from the Middle Edo period down to the Meiji era, not only flood damages invited by the collapse of embankment, but also such incidents as ill damage and lack of the water for irrigation, because its river bed had been higher than the plain on both sides of the river.
Tracing the period as well as the cause to all over the basin of the river Takahashi, and furthermore, scrutinizing the socio-economical circumstances at the times when such a change took place, the author here tried to clarify the conclusive cycle system between the river bed rising and its pertaining phenomena (Table 6th).
Summing up, there were zones of the Tatara_??_industry (sand iron industry by foot-bellows smelting process) at the valley of the upper stream Takahashi from ancient times. Stabilizing and extension of the embankment had already begun to develop the newly reclaimed paddy-field at the lower stream area from about the 15th century onward. Since then in the latter half of the 17th century several records came to be found in the ancient manuscripts, indicating that earth and sand which were washed down in the sand iron gathering process, increasing in quantity, had caused the river swelling; the more waste they flowed down after digging out, the more unwiedly it had been accumulating at the basin and shifted the delta toward the lower stream area. Physical aspects favourable for the newly reclaimed paddy-field development had been rebuilt up in such a way. In keeping pace with it, additional stabilizing and extension of the embankment accelerated the river bed swelling more and more.
In the latter half of the 18th century, enormous quantity of earth and sand were going to sweep away from the granite mountainous district in consequence of the reckless deforestation at the hilly countries, and the river bed of the Takahashi had been still continuing to swell higher. These rising of the river bed closely interrelated to the socio-economical fluctuating periods, and almost all their timing were coincidated with each other. The same process are found more or less at many other rivers which flow from the Tatara industrial zones such as the Chugoku mountainous district of Japan.
