Name: 為什麼風暴潮是颶風中最致命的部分？ (Why a storm surge can be the deadliest part of a hurricane)
Uploaded: 2021-01-14T07:21:42.000Z
Duration: 4 min 1 s
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In late August 2005, Hurricane Katrina was moving its way across the Gulf coast.

Dangerous, but in a region with a long history
of Category 4 and 5 hurricanes, it wasn't

Katrina was only one day away from the Louisiana
coast when the mayor of New Orleans issued

The sea level had already risen in a phenomenon
called storm surge.

Water rapidly rose up against the city's levees,
a series of walls designed to keep the area

Before Katrina made landfall, the levees broke.

A wall of water rushed into the city, trapping
thousands.

What followed was one of the worst natural disasters in US history.

"We're expecting storm surge of 20 to 30 feet high"

"A levee broke during the height of the storm"

"There are bodies...uh... floating in the water there."

Storm surge was the main cause of death during
Hurricane Katrina.

In fact it can be the most dangerous part
of any hurricane.

It occurs when strong winds from an approaching
hurricane push water into the shore.

As the sea rises, a bulge of water sweeps
over coastal areas, causing destruction along

These are the normal astronomical tides at
Dauphin Island to the east of New Orleans.

When you compare them to the water levels
during hurricane Katrina — you can see the

What makes this rise dangerous is that it
starts to build up before the hurricane makes

So the coastal flooding from it can make evacuation
procedures and the impact of a hurricane much

In 2008, hurricane Ike caused a big storm
surge around Galveston, TX a day before landfall.

The rising water cut off evacuation routes
stranding hundreds.

More recently, the National Hurricane Center
issued dire warnings for the storm surge accompanying

Hurricane Irma, the most powerful storm to ever rage through the Atlantic Ocean.

Rising sea levels caused by global warming
increase the risk of storm surge.

But there are many factors that can change
its size and strength.

For example, the largest one recorded before
Katrina was about 22 feet, during Hurricane

But Camille was a category 5 storm with 190
mph winds.

Katrina was only a category 3 with 130 mph
winds, but it had a storm surge of about 28

Katrina had slower winds than Camille but
it was twice as wide, which dramatically increased

These calculations help forecasters warn communities
at risk.

But they're often not enough to prevent
damage on the ground.

This map shows the highest storm surge events
worldwide since 1880.

In the US, the eastern and southeastern coastlines
are among the most vulnerable areas for storm

Along the east coast, hurricane Sandy got
its strength from a massive storm surge in

On the Gulf Coast side, places like Texas
and South Florida have seen multiple hurricanes

so they've built infrastructure to help defend
against excessive flooding.

Levees and seawalls are designed to stop or
redirect rising water away from cities.

But even those can be inadequate, as seen
during hurricanes Katrina and more recently,

What really concerns experts, though, are
places that don't experience a lot of hurricanes

This map shows that in the event of a big
hurricane, based on the characteristics of

the shoreline, the coasts of Northwest Florida
and Georgia would be at comparable risk to

These areas have shallow water, which means
sea level can rise faster and water can reach

further inland making the flooding worse.

But they've seen fewer hurricanes than the
Gulf Coast and they are likely to be less

So when a major hurricane like Irma hits low-lying
areas like these, the storm surge can be the

first and deadliest thing headed their way.

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為什麼風暴潮是颶風中最致命的部分？ (Why a storm surge can be the deadliest part of a hurricane)

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