- Extreme rain events are increasing at an alarming rate in the US and all over the world, but the problem isn't the amount of rain that falls in any one place, it's how long it takes the rain to fall.

And fascinating new research sheds light on exactly how that's changing.

Over the last century, global precipitation has only increased by 0.04 inches per decade.

But looking at individual regions in the US, we can see that some places have experienced 30% more rain over the same period.

However, more rain isn't the whole story.

That's why the organization First Street created a groundbreaking risk map that shows a big change in what NOAA calls 100 year floods.

These are events so extreme that the odds of them happening in any given year are about one in 100.

- 100 year precipitation event is occurring more often about once every seven to eight years in the most extreme cases.

- And that matters because infrastructure like sewer systems are built with this metric in mind.

But why the change?

It's because a warmer atmosphere is a thirstier atmosphere, meaning it can hold more moisture - For each additional increase in temperature.

By one degree Celsius.

The air can hold 7% more water - Vapor.

And that's fundamentally changing the hydrologic cycle.

Dry times get drier and wet times get wetter at an exponential rate, and not only just on a yearly scale, but down to the hour and the minute.

So First Street reanalyzed rainfall data across the US down to the minute their analysis uncovered an important trend and led to a new flood risk map of the United States.

It turns out that some places currently seeing less annual precipitation and more drought should also expect more flooding.

In this episode we're gonna look at this map to see what regions are most at risk and how we can adapt with all this additional water.

- This is not something that anyone should go through when it comes to a disaster, especially a hurricane.

- We can learn a lot from New York City when it comes to extreme rain because they're getting so much of it.

Just last September, the city saw nearly eight inches of rain in a single day.

- A place like New York City used to be very, very green, and it was covered in lakes and streams.

And over time it's been filled in.

The - Same is true in nearly every city.

We've replaced natural permeable surfaces with concrete and asphalt.

Nearly 72% of New York City is now covered in impermeable surfaces.

So instead of a natural water system, runoff has to be managed by a sewer system designed for a climate that no longer exists.

- The original designers that built our sewer system did not know that we were gonna have 3, 4, 5, 8 inches of rain.

- One in a hundred year event in New York City actually occurs about once every 35 years.

- This is a new problem, so they can only manage about one to two inches of rain per hour.

- Our infrastructure just can't keep up with all the rain that we're getting.

And the NOAA maps, which are referred to as Atlas 14 and Atlas 2 that we use to project flood risk and figure out where to upgrade our infrastructure for flooding, events aren't keeping up with the rain either.

- They use traditional historic methods for measuring precipitation risk.

And for a long time, that was perfectly fine.

The problem is if you have an increasing precipitation trend, then all of a sudden now the average doesn't actually capture what the current events are.

It actually pegs them back to a climate that could be as far as 20 or 30 years ago.

- In other words, the NOAA maps look backwards and not forwards.

So First Street decided to take a different approach to NOAA's data.

- Our report was really focused on the extreme precipitation events as opposed to the average precipitation levels across the country.

And it's not necessarily that we're seeing more of these events, but when we seen them, they're more severe, we're seeing more severity in the intensity of the rainfall events over shorter durations, which is causing more - Flooding.

Amit Shivprasad lives in Hollis, Queens.

His neighborhood has been impacted by flooding events for a long time, but recently it's gotten worse.

Looking around the area has very few green spaces to absorb Rainwater and Amit learned that this area used to be an actual lake.

- So this is actually our house where you guys are right now.

So if if you look, it's actually sitting in the middle of a pond right now, and this is what the pond looked like back in 1928.

If you - Look at an old map of New York City and see where all the creeks and the lakes used to be, and then you look at today's flood map, you can actually see that it's pretty much identical.

- FEMA's 100 year floodplain map derived from NOAA's Atlas 14 directly impacts the cost of and access to flood insurance.

But since the map doesn't include flooding from rainstorms, many communities are left out.

And as a result, overexposed - Flood insurance was never sold to anyone in this community because we don't live in a flood zone or a FEMA hundred year map.

But - Flooding has devastated this community.

In 2021, after Hurricane Ida made landfall as a category four, it traveled up the Eastern US dumping record breaking rainfall in its path in New York City alone.

It dropped over seven inches, peaking at three inches of rain per hour.

Amit's neighborhood was not prepared.

- It started off as a normal day, had dinner with my folks and all the warnings start to go off.

Ran downstairs, grabbed my poncho, with me and my dad took our shovels and rake went out to clean the basins like we do every single time it rains.

But - The sewer basins on Amit's street weren't functioning that day.

- City was doing construction and they pretty much had all the basin covers covered.

Notice as the rain was coming in higher.

So I ran up and grabbed my keys, moved the truck up the block before I got back down the end of the block, the entire street was flooded.

- The flooding killed 13 people in New York.

- 11 of those people died in flooded basement apartments, most of them here in Queens, 43-year-old Phamatee Ramskriet and her 22-year-old son, Krishah, also known as Tara, and Nicholas could not survive last night's rushing flood waters crashing through the wall and pouring into their basement apartment.

- Tara and Nicholas were tenants in Amit's family's basement.

Before Ida he lifted the doors to his home, three to four feet to prepare for flooding, but the storm brought too much water.

He no longer rents out his basement and now uses the space for community events.

- Unfortunately, the wall collapsed and that's the reason why all the destruction happened.

So I've done my part where it comes to repair.

I just pray and ask God that it never floods again.

That's all.

- Ida resulted in $75 billion in damages across the U.S. Over 33,500 buildings in New York City were destroyed, and Amit's remodel alone cost over $344,000.

But not all areas were equally affected across the Hudson Hoboken, New Jersey didn't suffer the same flooding, and this is partly because of their efforts to adapt to this new climate reality.

- Flooding has always been a problem in the city of Hoboken.

We were originally a tidal marsh, actually.

The area where we were standing, it was marshland.

All of these low-lying areas that were marsh that were filled in for industrialization in the early 19 hundreds are very subject to flooding today.

We also have a combined sewer system where our storm water and our sewage flow into the same pipes.

Now with climate change, we're seeing more frequent storms, more severe storms.

- To address the flooding issues, Hoboken has been building resiliencity parks around the city.

We went on a tour of the largest park to understand how these green spaces operate.

- This is one of the 19 rain gardens that is in resiliencity park.

And these rain gardens will manage water during a rain event.

You'll see that it almost looks like a pond.

Water is slowly being delayed from entering our storm water system.

It's filtered through the rain garden through all the plants and the soil.

Then that water slowly drains into the underground tank that's below the park and then goes out to our sewer system.

And that's all water that then is not on our streets.

During a rain event, our million gallon detention tank that is under this lawn can detain storm water that comes from the park site itself, as well as from all of Northern Hoboken - And it's working.

Hoboken has seen an 88% decrease in flooding events since installing these mitigation measures.

And only time will tell if these measures hold up against future climate changes.

But it's strong proof of concept.

The comparison of Hoboken and Hollis also follows another trend.

Recent studies find that race and wealth play a big role in where natural disaster recovery efforts happen, and this impacts safety and economic outcomes for residents.

A study from 2018 found that in areas with at least $10 billion in damages from a natural disaster, white families actually saw a wealth increase of about $126,000 post recovery while black families saw a wealth decrease of $27,000.

This map shows the extent of this wealth gap in some major cities across the U.S. Hoboken is 64% white while Amit's neighborhood in Queens is just 1.4% white, - 1.3 million.

New Yorkers live either in or directly adjacent to a flood plain, and that's gonna go up to be over 2 million.

By the turn of the century.

Half of those people are considered low income by HUD, our federal government, and half of those people are communities of color.

- Hollis, which is Amit's neighborhood in Queens and the adjacent Queens village, underwent a $24 million sewer expansion from 2019 to 2021 to try to address the flooding problem.

However, the Hollis community still experiences frequent flooding.

- My neighbor across the street, every time it rains, she comes over to our house 'cause she's afraid that her wall is gonna collapse again.

And you know, it's, it's, it's a sad thing.

That everyone in the community is feeling the same way - As the climate changes and the wet times get wetter.

Intervention efforts become increasingly more complicated and challenging.

- And this is gonna be one of probably the biggest issues that we're gonna face over the next 20 years is gonna be where are we gonna stay and where are we gonna leave?

There's no one solution for every neighborhood or for every place.

- But there's hope for flood mitigation efforts.

Every dollar spent on flood mitigation sees up to an $8 return.

- So we can manage that water with green infrastructure and turn New York City into a sponge in every neighborhood in every place that we can possibly do it.

We'd like to absorb water, so that could be on our streets, it could be on our green roofs, or it could be in our parks.

- Now that we understand the challenges and opportunities to deal with urban flooding, let's get back to First Street's new risk map, which focuses mostly on flooding from heavy rainfall events.

- There's about 8 million properties currently in FEMA's special flood hazard area compared to our about 17.7 million properties.

Most of that, about 65% of that gap that we see is actually driven by precipitation - risk.

In fact, by FEMA's own estimate from 2015 to 2019, 40% of flood insurance claims came from outside of the high risk zones on the FEMA map.

But maybe the most surprising is the update to NOAA's flood maps.

This shows the difference between NOAA's maps and what First Street found where 100 year floods are now more like 35 year floods, like in the case of New York City.

Their study even found that in some areas, 100 year floods have now become just eight year floods, making them more than 12 times as likely.

- The Midwest in particular sees a lot of underrepresentation of those one in a hundred year events, places like Southern Indiana and Northern Kentucky around the Louisville, Kentucky metro area.

They're seeing the one in a hundred year depth from the NOAA Atlas 14 records as much as one in seven or one in eight years.

- According to First Street, not only the Midwest, but the entire Northeastern part of the United States has a hidden risk of extreme precipitation.

And even in Northern California, which is seeing a decrease in precipitation overall, the likelihood of a 100 year flood is now one in 35.

With climate change, we're seeing strange patterns and complex impacts to our weather systems.

We may not know exactly what a warmer world will look like, but it's clear that change is happening.

So it seems like it will be wise for us to adapt.

In this episode.

We've learned the stakes of flooding from these extreme rainfall events and looked at places like the City of Hoboken, a place that's doing a great job at navigating these changes to our hydrologic cycle.