Why New York and other cities don’t have a plan for floods

New York City is going through a tough time: How can we protect ourselves from floods? Ask Aggarwala at the University of Texas

New York City came to a grinding halt Friday as floods shut down roads and subways and inundated schools in one of the biggest storm-related emergencies since the remnants of Hurricane Ida hit in 2021.

How is flood risk changing with climate change? New York City’s commissioner of the Department of Environmental Protection, Rohit Aggarwala, said in a press conference today, “The sad reality is our climate is changing faster than our infrastructure can respond.”

What should a flood-proof city look like? The director of the Institute for a Disaster Resilient Texas and a professor of marine and coastal environmental science at the Texas A&M University were asked what they did.

Absolutely. Cities have more impervious surfaces and are sprawling outward with roadways, rooftops, and parking lots. The water has nowhere to go but downstream, and sometimes into people’s homes.

It is very important for cities to think about their drainage infrastructure, not just put it in place, but have it kept up to date and monitored over time. In the United States, we have done a poor job of that.

Even the systems that are designed today, they’re only designed for, for example, a five-year storm event. The United States’ baseline of risk is a 100 year event. The chances of an area getting flooded by the sea in a 100 years are 1 percent. That doesn’t mean you get a 100-year storm and then you can feel like you’ll be safe for another 100 years. It means there is a 1 percent chance every year.

The human-built environment has been a noted problem for decades. And to ignore that as the major cause of the problem right now, I think, would be missing the total picture. Our infrastructure is overwhelming, it is our development decisions and patterns of human impact on the landscape that we are most focused on, but it is a much longer, slow variable of influence.

There are four dimensions of a city that would be damaged by a flood. The first is avoidance, getting out of the way. It means building higher in some cases and pulling away from vulnerable areas in order to allow remaining ecological infrastructure to do its job.

The second dimension is to accommodate. There are some places where we want to let it flood. Whether that’s creating areas of retention and detention or that’s, again, letting these naturally occurring wetlands alone. We’re so used to fighting water. There are places where we want to let water flood in these landscapes and that’s why there are different types of accommodations.

The third component is resistance, which is all about the history of flood management in the United States: fighting the flood. Different ways to hold the water back are included. Our main strategy doesn’t work if we do that alone. That’s why I’m mentioning that as a third component, not the first.

The last component is communication, telling the story of risk. That’s providing information in a way that’s interpretable and actionable to those decision-makers but also individual residents to have them better understand what their risk will be so that they can take action.

The urban jungle is a bounty, not a burden: How the rains of the future can be spongier and healthier than the rain gardens of the West

Basement flooding is a huge problem in Houston, which is the epicenter for urban flooding in the country. Wealthy homes are the ones that are elevated really high and have all kinds of expensive systems in place to withstand floodwaters.

In the Netherlands, they put a precedent on protecting the socially vulnerable first. It’s not just income — it’s age, education; those are the populations that need to be protected first.

On a warming planet, individual storms will get more intense. This pain will be especially acute in urban areas, which are built on stormwater infrastructure designed to handle the rainfall of yesteryear. Think back to what the builders of the last century wanted: sewers and canals that funneled rainwater as quickly as possible into a river, lake, or ocean, before it had a chance to accumulate. It worked well most of the time. But over the intervening years, rare catastrophic flooding has been growing more common. Wastewater systems from ancient times are being asked to get rid of ever- bigger storms.

Los Angeles is implementing rain gardens, as well as distributing rain water into spreading grounds with big dirt bowls. In the drought-wracked American West, this will send as much rainwater as possible back into aquifers, to be tapped for drinking water as needed.

Green spaces don’t just mitigate flooding. The landscape of the city is changed to improve residents mental health. They prevent pollutants from reaching sensitive water bodies like rivers. And when the weather is hot, they cool neighborhoods because plants “sweat.” This reduces the urban heat island effect, or the tendency for cities to get far hotter than surrounding rural areas. If these green spaces were urban farms, they could do all that while also producing food.

The city of the future may be spongier in ways that are obviously verdant or more subtle. As the planet warms, the rains of the future could be a bounty, not a burden.