Associated with port construction or land reclamation projects, we have some experiences to construct tidal flats so as to enhance or rehabilitate damaged coastal ecosystem or to create new flat topography with inter-tidal ecosystem. Three sites are reviewed and compared as case studies. For suitable management and designing, it is necessary to understand the ecological system in coastal tidal flats Elemental components are also summarized which support sound benthic activities. Comprehensive approach is required for the benthic ecological system. Sustainability, self-recovery and independency will be the key concepts for the system evaluation. Sound nutrient circulation is essential for the sy stem stability- We should also consider the natural fluctuation of the environmental condition as well as the tidal topography. Environmental diversity and environmental gradient in a tidal flat may support the self-recovery of the ecosystem through Our 'Design' of constructed flats will contain some kind of aerial margin or spatial capacity which assure the nature to create and alter the detailed morphology or micro-zonation of the benthic ecosystem.
1. INTRODUCTION
Coastal tidal flats are drawn our attentions for their vulnerability and high activity of benthic ecoystem.
Coastal shallow sea areas are characterized by features common to areas where land, sea and atmosphere meet.
In these areas, we can find high biodiversion and productivity supported by such factors as, ? the exchange of large volumes of oxygen, carbon dioxide and other gases with the atmosphere, ? the environmental gradient of water temperature, salinity, organic concentration and other factors with distance from the shore, and ? the variegated topography oｆ the sea bottom due to wave and tidal effects.
Recently, habitat remediation is becoming one of the most important measures for not only remediating damaged ecosystems, but also harmonizing coastal development with coastal ecosystems. Three constructed tidal-flat along the Japanese coast are compared in this paper. The status of, and also problems related to, tidal-flat construction/management technology are mentioned. Tidal flat is characterized by its unique flat topography in shallow coastal areas. It repeatedly emerges from, and submerges under, seawater due to ebb and flood tides.
2. CASES OF TIDAL FLAT REHABILITATION
AND CONSTRUCTION IN JAPAN
2-1 Case studies
Associated with port construction or land reclamation projects, we have some experiences to construct tidal flats so as to enhance or rehabilitate damaged coastal ecossystem or to create new flat topography with inter-tidal ecosystem. Three sites are reviewed as case studies. Those are, a) Gamoh Flat at Sendai Port, b) Itsukaichi
