An assessment program for simulating the tidal flow and ecosystem in the sea around a very large floating structure or a Mega- Float, developed in the first phase of the Mega-Float project in Japan is presented. The model consists of two parts, a hydrodynamic model and a marine ecosystem. Tidal currents, water temperature, salinity and water density are calculated in a bay with/without a Mega-Float in the hydrodynamic model. A marine ecosystem model including nutrients, phytoplankton, zooplankton and organic matters has developed in detail. Simulation results with/without a Mega-Float of 4.75 km length, 1.5 km breadth and 1.2 m draft are presented in Tokyo Bay. Changes of marine environmental factors by the installation of the Mega- Float are studied for some configurations of a Mega-Float and breakwater. Lastly, some potential technologies for the environmental preservation and restoration are studied.
Predicting the marine environment changes caused by installation of a Very Large Floating Structure or a Meg.-Float is one of the technical challenges in introducing a Mega-Float into practical use. It has been known that the marine environment such as flow and ecosystem shows complicated changes due to a various natural conditions. So that on prediction of the environmental changes caused by installation of Mega-Float with precision, it is well recognized that the prediction of ecosystem changes including low-level planktons, organic matters and nutrients must be done after the prediction of 3-dimentioanl flow changes including wind driven current and density current due to thermal and salinity concentrations changes. In "An experimental Research of Very Large Floating Structure" by Technological Research Association of Mega-Float launched in 1995, researchers have been conducted studies taking these matters into account. It has been revealed through numeral calculations that the Mega-Float is expected to affect on the flow slightly 1)2).
