Here's why New York City floods are getting worse and more frequent

• NYC floods are getting worse.
• Being surrounded by water amid rising sea levels doesn't help.

It's another sopping wet day in New York as heavy rains bring forth mass flooding across the city.

Multiple subway lines are suspended amid the flooding, cars are stuck on thoroughfares, and people are wading through knee-deep water to get to their destinations.

If you feel like you've seen this film before — and recently — you're not wrong. Flooding is getting worse and more frequent in the city. Here's why.

1. Rising sea levels

While sea levels are rising everywhere, they are a prominent threat to New Yorkers. They've risen by a foot in the last 100 years and are predicted to be about six feet higher than they are now by the end of the century, according to the city's own estimations. By 2050, sea levels may be 11 to 21 inches higher, according to New York City's guide on hazard mitigation.

And if water isn't rising from below, it's falling from above. The climate crisis has worsened excessive rains, making flooding even more likely.

2. Land sinking

New York is heavy. On top of the nearly 9 million people that may find themselves in the city on a given day, the city has about 1 million buildings, from skyscrapers to aging brownstones, according to the hazard mitigation guide.

All of that weight causes a sinking phenomenon called subsidence, the gradual sinking or caving in of land.

New York is sinking at an average rate of 1 to 2 mm per year, though some areas of the metropolis are sinking even faster. To put it in context, the city is sinking at the same rate as Venice, Italy, famously known as the "floating city," Insider previously reported.

3. Water literally everywhere

The city's five boroughs touch more than 520 miles of shoreline collectively. The close quarters with so many rivers, bays, and waterways leave the surrounding areas susceptible to flooding.

Officials have considered a nearly $120 billion sea wall to protect the city from storm surges and flooding, though some say the climate crisis would make the wall superfluous, The New York Times reported.

4. Wilting infrastructure

The city's aging infrastructure furthers the risk of flooding. The sewer system, which is combined with the storm system, is only built to handle 1.75 inches of rain per hour, according to The Washington Post. When heavy rainfall overtakes the system, the stormwater has nowhere to go.

Up to 3 inches of rain have already fallen in the city as of midday Friday, and at least another 1 to 2 inches is expected, according to the National Weather Service.

"When this happens, the combined sewer overflows (CSOs) — the mix of excess stormwater and untreated sewage — flows directly into the waterways," reads New York's hazard mitigation guide.