Koiwa irrigation canal was the main diversion canal for Kami-Shimo-no-Wari canal, which water source was Koaitamei (Mizumoto Park today). In the middle of the Edo period, Kyoho 14 (1729), Yasobei Izawa, who was the shogunate accountant of the 8th Shogun Yoshimune Tokugawa , closed off the old canal of the Tone River and built Koaitamei (small pond), and developed the Nakagawa River and Kami-Shimo-no-Wari canal. Kami-Shimo-no-Wari canal was the irrigation water for more than 50 villages in the Higashi Kasai Territory, passing through the Iwatsuki Bridge, the Koiwa Irrigation at the Ozekiwaku, the Higashi Ibori near the Niijyuku Village and Magarikane Village, and the Nishi Ibori and Naka Ibori near Hosoda Village and Okudoshinden. Koiwa irrigation canal, called Shimonowari, was the main irrigation canal to current Edogawa City. At that time, the Kasai territory was a rice paddy area with two major irrigation canals which were Kami-Shimo-no-Wari canal and West Kasai Canal. The area was a rice-producing area of 30,000 goku (about 350,000 km2) in Kasai. Vegetables such as Komatsuna (Japanese mustard spinach) were grown in the fields, and had important role as a farming area to supply Edo, a major consumer area. With the progress of urbanization, these irrigation canals gradually lost their role, and after the World War II, It became a drainage channel into which wastewater from factories and households flowed. In April 1964, it was transferred to Katsushika City, and it had been maintained as a green road with the completion of the sewerage system to the present day.

February Heisei 2 (1996), Katsushika City