Rockaway, like many coastal neighborhoods in New York, is extremely vulnerable to water. More than 120,000 people live on the Rockaway peninsula — a slender mass of land that stretches across 10 miles with the ocean to the south and Jamaica Bay to the north.

One recent report by the Waterfront Alliance estimated that 61 percent of Rockaway residents, or 74,800 people, had a one-in-two chance of a major flood in their homes by 2060.

“This is the story of our time,” said Robert Freudenberg, the vice president for energy and environment at the Regional Plan Association, an urban research organization. “Adaptation will require one of the biggest investments that we’ll need to make in the region.”

On the beachside of the peninsula, the Army Corps has proposed building 13 new jetties and extending five existing jetties — rock formations that jut out perpendicularly to trap sand and build up the beaches they protect.

Sand is widely regarded as an effective mitigator of storm damage: A wider beach can dissipate the energy of storm tides.

But a significant amount of the sand replenished in Rockaway by the Army Corps in 2014 after Sandy has already been washed away. In certain sections of Rockaway Beach, the water has eaten away at the shoreline, reaching the sand dunes and the boardwalk that shield the neighborhood.

Jetties are meant to slow this type of coastal erosion, a natural phenomenon exacerbated by climate change, experts say.