Tanimizu Terraced Paddies
Although the Shimabara Peninsula has many farms, they are rarely used for rice cultivation. The slopes of the mountains are too steep to be terraced into rice paddies, and the beautiful Tanimizu terraced rice paddies could only be built after a landslide partially filled this valley.
During the Edo period (1603–1867), wealth was measured in koku of rice. A koku was equivalent to about 5 bushels, or approximately the amount of rice needed to feed one person for one year. Subsequently, rice functioned as a de facto form of currency, and taxes were levied in koku as well. Without rice, participating in the economy was very difficult. Shimabara was historically a poor domain because the two main conditions for successful rice cultivation—a large amount of water and flat land—were not present on a mountainous peninsula with no large rivers.
In the distant past, this valley was the site of a landslide that brought many large rocks down from the mountains, flattening the land and providing material to make retaining walls for the terraces. The combination of relatively high rainfall on the western side of the peninsula and the underlying layer of impermeable rock created the conditions for rice cultivation.
The terraced paddies have allowed the people here to take advantage of this geological blessing for several hundred years. One of Japan’s first hydroelectric power plants was built in this otherwise out-of-the-way region in the early 1900s.