Although many artificial tidal flats had been constructed in Japan, there was not enough monitoring data that can prove the restoration of the natural environment after the construction of the tidal flats. Hiroshima Port and Airport Office at Chugoku Regional Development Bureau constructed three tidal flat as environment restoration projects in Onomichi-Itozaki Port area, Hiroshima, Japan. Total area of three tidal flats is c. a. 60 ha. After the completion of the tidal flats, geo-morphological change, sediment quality, benthos abundance, and sea-grass(Zostera marina)habitats have been monitored since 1984 to 2002. Especially, during FY 2000 to 2002, high biological diversity as natural tidal flats, abundance of many endangered spices, and 8 ha of sea-grass(Zostera marina)habitat restoration had been observed.

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