Ariake Sea
Major land reclamation projects have occurred which added plains in the Ariake Sea. The biggest is the Isahaya Bay reclamation project (諫早湾干拓事業) by the Ministry of Agriculture, Forestry and Fisheries that started in 1989. Embankments and sluice gates were built and a total of 35 km2 has been reclaimed as of 2018.