Saitama (city) city boundaries. The western portion of the city lies on the lowland created by the Arakawa River along with those created by small rivers such as the Moto-Arakawa River, Shiba River, and Ayase River. The rest of the area mostly resides on the Ōmiya Plateau lying in the north-south direction. Dispersed in this region, major rivers flow southward, almost paralleling to one another. Saitama has ten wards ("ku"), which were assigned official colours as of April 2005: Saitama's economy is principally constituted by commercial business. The city is one of many commercial centers of the Greater Tokyo area and serves
Arakawa River (Fukushima) ineffective, and the river continued to periodically flood, culminating in a large-scale flood on August 5th, 1986. In 2004 the Arakawa River's flood control system was completely overhauled, and 13 new check dams were built along the main river and numerous other dams built on its tributaries. In 2008 the Agency for Cultural Affairs designated the Arakawa First Check Dam as a Registered Tangible Cultural Property. In 2007 the Arakawa River tied with six other rivers for having the best quality river water in country based on biochemical oxygen demand tests conducted by the Ministry of Land, Infrastructure, Transport and