Repeated tidal ebb and flow support the lives of various water creatures and provide a place for spawning and larvae to grow. It absorbs nutrients and carbon dioxide, supplies large amounts of oxygen to the sea, and promotes the decomposition of organic matter by activating bacteria. In this way, the sand and mud of tidal flats purify a lot of dirt that flows into the seawater. In addition, many of the small benthic animals (lugworms, shellfish, crabs, etc.) that inhabit tidal flats prefer to eat organic matter with bacteria on them.
From the Edo period to the early Showa period, as the town developed, land reclamation was actively carried out mainly in the estuary area, but many tidal flats remained in the inner part of the bay. It was not until the late 1950s, during the period of rapid economic growth, that man-made structures began to fill most of the coastline. As industrial demand subsided, the purpose of reclamation shifted to the provision of large residential and commercial lots.