Explained: Why New York City Keeps Getting Flooded

New York is under a state of emergency after heavy overnight rains flooded the streets, subways, and airports on Friday. But this isn't the first time that New York is witnessing such a situation. And the situation may turn worse under the rising impact of climate change, say experts.

The drainage system in New York City gets overwhelmed due to excessive rain in the city. It can handle a maximum of 1.75 inches of rainfall per hour, but the city received over 2 inches on Friday. The drainage capacity breach is believed be the main cause behind the flooding.

"This changing weather pattern is the result of climate change, and the sad reality is our climate is changing faster than our infrastructure can respond," Rohit Aggarwala, commissioner of New York City Department of Environmental Protection, told The New York Times.

In over half of New York City, the drainage system combines the storm water with the sewage in the same pipes. When the flow in the pipes gets too much, the water enters the local waterways. As the sewer system is overwhelmed, untreated wastewater ends up in the basements of residents and businesses.

Scientist Michael Mann from the University of Pennsylvania said flooding is "worse than a new normal. I call it a new abnormal".

Underlining the causes of excessive rainfall, he said climate change warming up the planet and warmer oceans mean more moisture is in the atmosphere that can trigger rains and lead to flooding.

"But climate change is also altering the behaviour of the jet stream, and some of our work suggests that it is leading to a wavier, slower jet stream associated with stalled weather systems that remain stuck in place for days or even weeks on end - that's when you see the worst flooding events," the scientist added.