The key to fighting the urban doom loop might be a downtown beach

• Urban waterfronts are neglected in many American cities. 
• But they have huge potential to revitalize cities and make them more equitable. 
• Urban rivers, lakes, and parks can also be the key to making cities more resilient to climate change.

On a sunny, 80-degree Saturday afternoon in late October, Mia Olis left her home in Chelsea to soak up the rays on Manhattan's brand-new — and so far only — public beach.

Raised in Hawaii, Olis loves the water and surfing. But Rockaway Beach — more than an hour away by subway — was too far a trek that day. The 1,200 tons of sand near Greenwich Village along the Hudson river would have to do.