Washing upriver
The 2030s were a bad decade for New York City and Long Island. A two meter rise in sea level, supposedly caused by melting icecaps, combined with three Category 3 hurricanes were just too much for the metropolitan area. New York City's sewer system, always on the edge, collapsed in two of those hurricanes, and tunnels and bridges sustained major flooding and damage. Long Island suffered massive erosion, with two one-mile channels cut across the south fork of the island and major damage elsewhere. The Port of New York and New Jersey was devastated.
Connecticut and New Jersey sponsored major legislation to move homeowners from their coastlines to deeper in their interiors, covering costs for people who never realized they might be in a floodplain, and building new high-speed trains to help those people reach their workplaces in almost the same time it had taken them before.
That cost those states a fortune, but New York had a much harder problem: the destination where all those people were supposed to be headed was itself in danger of washing away. By 2042, the outlines of a plan began to emerge:
A new Manhattan would emerge, three stories higher than the old. Existing buildings less than five stories tall would be demolished, and Central Park would become an enormous pond with built-up islands. Tall buildings would be required to move all critical infrastructure to their new fourth-floor basements, and subways - newly laid out inside the elevated area - would run at the old third and fourth floors. Only about 30% of the island would remain in use, but it would gain much stronger connections to Connecticut, New Jersey, and Upstate.
Brooklyn, Queens, Staten Island, and Long Island, would shrink drastically, with neighborhoods above 100 feet in elevation surviving but the rest converted to agriculture and other similarly non-permanent uses. The south shore of the island would be largely abandoned, turned into parkland served by hotels on relatively higher ground.
New restrictions on the lower Hudson Valley similarly required construction to move to the higher ground.
The Port of Albany, already benefiting from growing Erie (Barge) Canal traffic and the survival of its railroads, would be massively expanded to replace a significant part of the former Port of New York.
As in Connecticut and New Jersey, the State of New York built massive high-speed rail down the Hudson Valley and along the Thruway Corridor to help relocated residents connect to their former center of business.
All of this cost a fortune, with little assistance from the beleaguered federal government, which was already dealing with the near-complete relocation of Florida residents to other states. Leaders in the key finance and media industries rallied to raise private funds for the redevelopment of Manhattan, easing the burden on the state government. Land values along the old Thruway corridor skyrocketed, though the state used its powers of eminent domain to break several logjams that threated redevelopment.
As of March 2050, the resettlement is almost complete. Residents who refused initially to leave their homes have mostly surrendered to continuing weather problems and the decay of their surrouding infrastructure. The rebuilt Manhattan is widely praised, though the use of the Port of Albany has limited New York's access to the largest freight shipments. Both wealth and population are much more evenly distributed across the state, and the upstate-downstate divide that many feared would create catastrophe rarely emerged.
