In the Edo period, as many domains in western Japan were small and had narrow alluvial plains, they developed rice fields even in the mountains in order to increase Kokudaka (assessed yield) which was the economic base of the domain, and a large number of rice terraces (on steep slopes), which are called Tanada today, were developed.
江戸時代の西日本は、藩の規模が小さく、沖積平野も狭いところが多かったため、藩経済の基盤の石高を増やすために山間地にまで田圃がつくられ、現在でいう（急傾斜）棚田が多くつくられた。