Cities evolve. They expand to accommodate growing populations. They alter their infrastructure for new technologies, such as automobiles and trolleys. Today, we even see cities like London, Paris, and Berlin moving traffic away from their city centers, and some are making changes to become sponge cities, urban settings redesigned to better deal with increased water levels.
New York City has seen much-increased flooding in the last couple of years, with Hurricane Ida hitting the city with more than three inches of rain in one hour, and now plans to take steps to make the city more porous.
A more resilient Big Apple
A changing climate promises larger storm surges and increased rainfall for coastal cities like NYC. As a largely concrete city with little absorbency, this is going to lead to more and more flooding for which they need to prepare.
“New York City is preparing for both chronic storm events — these cloudburst events that we see occurring more and more frequently — as well as extreme storm events like Ida,” says Jennifer Cherrier, a professor of earth and environmental sciences at Brooklyn College.
Luckily, the city that never sleeps has plans in place.
Green infrastructure
A recent Arup report showed that about 39 percent of the city is already green space like parks, street-side lines of trees, and green waterfront areas. The soil of these green spaces helps a lot to absorb floodwater.
“We’re trying to demonstrate that if you’ve got good land-use planning and you focus on the areas where you’ve got good permeability, these are good win-wins in terms of creating sponginess within your cities,” says Vincent Lee, Arup’s global water skills leader.
New York also naturally has higher amounts of sandy soil which absorbs water better than clay-based soil. This being the case, certain areas of the city will absorb better than others, and some areas might need more absorption. Closer analysis will enable the city to plan where to strategically green up, and the city has already invested $1 billion in expanding its green infrastructure. Some programs even incentivize residents to build rooftop green spaces and gardens to help absorb water. But is this enough?
Gray infrastructure
New York’s very old sewage system also needs to be expanded to make room for more water, from its current 1.75 inches to 3.5 inches of rain per hour. While this would be an enormous, time-consuming, and expensive undertaking, the need far outweighs the cost. Many in the city also see the importance of investing in new ways to move water in this city. In the last few years, the city has invested in the capacity expansion of Queens to the tune of $2 billion.
