A new community could be floating on gigantic rafts in Tokyo Bay by 1982, a plan being discussed as one solution to Japan's over-population problem.

Proponents of the floatiing communities say they might help alleviate the housing shortage while at the same time providing needed recreational facilities and refuse from Japan's periodically devastating earthquakes.

But one expert involved in researching the plan had a warning: sea city citizens should not be prone to seasickness.

Masanobu Shinozuka, professor of civil engineering at New York's Columbia University, and a Tokyo-based architectural firm, Kikutake Architect, stores, warehouses and parks on the rafts at a total cost of around $700 million.

The Japanese National Land Development Agency authorized Kikutake to study the possibility of constructing a floating city.

Shinozuka said financial support is yet to be secured, but funds are expected from a consortium of banks, including the long-tern credit bank of Japan.

Under present plans, 42 steel and concrete rafts will be constructed, each measuring 170 feet by 700 feet, Shinozuka said.

He said the modular units, open-bottom platforms with subdivided air chambers, will be connected to make an island, which will be anchored to the sea bottom.

The professor said they will be buuilt "not far" from the mainland and connected to it by movable bridges. "As the bridges will be short, they will be simple ones, something like the gangplank of a ship," he said.

If the rafts were floated far from the land, huge bridges would be needed and the water would be too deep to anchor them, Shinozuka explained.

"The water should not be deep, but not too shallow either - 33 to 50 feet would be ideal."

The islands will be surrounded by a concrete structure to protect them from the impact og high waves.

According to Shinozuka's calculations, the sway and roll of an island would be slight and slow even when there is a very high wind and people should be affected little.

Architect Kiyonori Kikutake of the Japanese firm, and advocate of the floating city, hopes to construct 333-foot-high apartment buildings on the islands.

Shinozuka, however, thinks rolling might be more of a problem for people in high buildings. For this reason, he thinks it more realistic to use the floating islands for other than residential purposes.

"It is theoretically possible and significant to build residential communities on the sea. However, there still are unknown factors, such as possible seasickness," Shinozuka said.

He stressed the effectiveness of such a rafts as an emergency center at a time of natural disaster.