Will New York City’s new mayor guard the city against climate change?

When Superstorm Sandy slammed into New York last October, it brought the nation’s largest city to its knees. Sandy’s powerful storm surge knocked out the public transportation system, plunged the lower half of Manhattan into total darkness, wiped out several coastal neighborhoods, and left nearly 50 residents dead. Recovery was slow and expensive (the storm caused an estimated $19 billion in damage), and in many areas, it still drags on.

A year later, despite a few preventative steps taken by the city and its power company Con Edison, New York would be crippled anew if another Sandy-level storm were to strike. Experts on climate change warn that if the city doesn’t move faster, rising sea tides and more extreme weather events could plunge the city’s low-lying areas ― including Lower Manhattan, a center of world finance ― under water.

“I recommend a discussion about …‘how safe is safe enough,’” Bas Jonkman, a professor of hydraulic engineering at Delft University of Technology in the Netherlands, said to Yahoo News. That country's capital, Amsterdam, is a water-bound city like New York and has been on the cutting edge of flood prevention.

New York City has focused on protecting itself against 100-year floods, which have a one percent or less chance of occurring each year. But with rising seas, that’s not enough, Jonkman said. “In the Netherlands, we are protected against one thousand to ten thousand year return period flood events,” he said.

Mayor Michael Bloomberg released a $20 billion plan last summer to address such concerns, recommending 257 projects like building flood walls, sand dunes, levees and natural wetlands around the city’s coastlines. The plan stopped short of recommendations from some climate scientists to build giant floodgates in the harbor that could be closed when a storm approaches, sealing off Lower Manhattan from rising seas.

But delivering on the plan’s recommendations would still be a massive infrastructure undertaking that would require cooperation and funds from federal and state authorities, as well as approvals from various zoning boards. Making its fate even more uncertain is Bloomberg’s departure at the end of the year. Bill de Blasio is the leading candidate to replace the current mayor and a strident critic of his policies.

Bloomberg aides are preparing reams of material for his successor on the mayor’s post-Sandy response and planning — a subject the mayor himself insisted should be a prominent part of the “smooth transition” he’s pledged to implement on Dec. 31, when he leaves office. The Bloomberg-created office of long-term planning and sustainability, which is leading post-Sandy planning, will also remain in place after the billionaire mayor leaves.

“Our goal is to hand basically a well-functioning machine, if you will, to our successors so they can decide whether they are going to have it run exactly the same way,” Deputy Mayor Cas Holloway told reporters on Tuesday.

The Bloomberg administration has so far only delivered on a few dozen of its own recommendations, like working to replenish sand on some beaches and tightening building codes, neither of which would do much to prevent future damage. Bloomberg’s flood plan is actually one of the few things the mayor has done that de Blasio has praised.

In June, de Blasio commended the mayor’s “serious ideas” and said he would use the plan as a “foundation” for his own approach, if elected. But de Blasio also raised questions about whether the plan helped low-income New Yorkers enough — saying he wanted a “special focus” on improving the resiliency of the city’s housing projects.

“Of course, many questions remain,” de Blasio said in a statement then. “As we review the plan, we must ensure that it truly serves the needs of low-income residents without a safety net — many of whom suffered the worst and longest lasting impacts from Superstorm Sandy.”

A de Blasio spokesman said the mayoral candidate is sticking by that statement and continues to review Bloomberg’s plan.

But anything less than unbridled enthusiasm from the city’s next mayor could result in inaction, given the scope and challenges the plan presents.

“These projects, all of them are going to need constant support and cheerleading — that’s the nature of any massive city project,” said a city official who declined to be quoted talking about the next administration. “There’s going to be this constant need for the next administration to continue to push and drive these things home.”

De Blasio — now the city’s public advocate — made his own recommendations after Sandy, such as integrating community-based organizations more effectively into the emergency management system, like training volunteers in first aid and other emergency response techniques.

Public housing residents, de Blasio said, “were prone to

suffering the worst effects of a natural disaster,” in a report released over the summer. “Vulnerable residents with special needs were confined in high rise buildings without access to basic social services, supplies or vital information,” he wrote. “Approximately one third of affected NYCHA residents were seniors.”

Meanwhile, Con Edison says it’s made more than $400 million in improvements to substations and other technology to ensure that Sandy-level flooding would never again cut power for days to half of Manhattan. A spokesman said the company has built a concrete flood wall around equipment and has proposed $1 billion in further improvements over a 40-year time span.

The public utility is asking for hundreds of millions in rate hikes to fund these improvements, which New York Gov. Andrew Cuomo is contesting.

--Yahoo News reporter Holly Bailey contributed to this story.