Early 50s Japan experienced many flood disasters from major rivers so the emphasis had been on river improvement work. In the 90s with increasing urban floods, the emphasis shifted from river to basin and in late 80s and 90s amenity and urban rivers and streams to improve quality of urban life became important.
In the 90s water storage and infiltration has become part of the flood control measures. An important aspect of this adoption was that it placed emphasis not only on the surface runoff control but also on the preservation of both surface and subsurface flows.
