The Ministry of Land, Infrastructure and Transport and Aichi Prefecture are jointly involved in various environmental rehabilitation and creation projects inside Mikawa Bay. New tidal flats and shallow waters have been created and capping has been conducted through the utilization of high quality dredged sand arose from the development of Nakayama waterway. Results from the monitoring survey in 7 years showed improvement in sediment quality and disappearance of oxygen depleted water column in the tidal flat. Also diversity of bivalves and other benthic organisms have increased in the tidal flat area, suggesting an improvement of the habitat environment. In addition, Bivalves play an important role in water purification function. When the increased purified nitrogen in water, owing to recovery of bivalves in the created tidal flat, is multiplied by the total project area (620ha), the amount of purified nitrogen becomes 815kgN/day. It is equal to approximately 2% of the whole nitrogen load to Mikawa Bay.
