What If Treasure Island Sinks?

There's been a lot of buzz recently about the Treasure Island Redevelopment Plan, which seeks to build about 6,000 new homes, bringing 13,500 new residents to the island, along with shops, services & supporting features.

Treasure Island was completed in 1938 for the 1939 World's Fair, then taken over by the Navy during World War II. It was created by filling in the bay, or actually by constructing a stone sea wall and filling it with sand and gravel dredgings from the bay and the Sacramento River Delta. (The name comes from the assumption that there would be gold in the dredgings.) The entire island (Treasure Island, that is -- not including the attached Yerba Buena island to the south, which is a natural island made mostly of solid rock that sits several hundred feet above sea level) is generally around four to six feet or so above sea level.

The Redevelopment Plan would put giant concrete columns around the edge of the island driven deep into the bay much to shore it up and stabilize it, so that during an earthquake, liquifaction would not cause it to sink into the Bay or cause its buildings to topple.

However, new urban neighborhoods, to be truly sustainable, must be built to last. Every effort has been made to make the new Treasure Island Revelopment Plan as sustainable as possible by building a carbon-neutral community, with an organic farm, solar and wind power, congestion pricing and limited parking to reduce automobile use. But once global warming kicks into full swing, and places like Greenland and the non-floating portions of Antarctica begin to melt, the sea level will begin to rise rapidly. By the end of this century, the sea level is currently projected to have risen by between 1 and 3 feet -- and that's the conservative estimate. By 2150, the sea level could be perhaps as much as 18 feet higher than it is today, given historical high-water marks for inter-glacial periods.

So, this is the question: What will need to be done to prevent Treasure Island from slipping beneath the waves during the lifetimes of our grandchildren, if current trends continue, the planet continues to warm, and sea levels continue to rise? Should planners now be thinking about a Treasure Island with a more Venetian layout, with canals between the buildings and tall buildings whose lower floors could be sealed against the water as it continues to rise, without rendering the entire structure useless or uninhabitable?

Or is this just so much useless speculation?