Abstract
The Ministry of Construction has already undertaken a policy, including the Comprehensive Flood Control Measures initiated in 1977 to prevent overflow by promoting penetration of rain into soil and building temporary rain reservoirs. Another example is the 1987 Overflow Control Measures, which sets forth measures to be taken when a flood runs over levees. And, the Flood Restraining Forest Belt to make the overflowing current run gently is proposed as a priority policy in 1996. These recently proposed measures confirm that the present situation warrants the revival of the Edo philosophy and approach of accepting a certain level of overflowing. With advanced technology available, floods would occur far less frequently than in the old days anyway. Nevertheless, the new approach and the Edo approach share the same acceptance that floods are sometimes inevitable.
One feasible way to implement the above policy would be to adaptively apply the flood restraining forest belt popularized in the Edo Era. Fortunately, we already have large levees; flood control would be complete if these belts were laid covering the levees.
Considerable attention has been paid to the semi-natural river engineering method and the multi-natural river engineering method. In this respect, the flood restraining forest belt may be the ultimate semi-natural river engineering method as it provides a corridor of a biotope connecting the forest and the sea, making the river more natural, and improving the riverside scenery. It is strongly recommended all the remaining forest belts be conserved and efforts be made to restore them where they have been lost.
