Original subtitles

Water may seem harmless,

but in huge quantities,

it can be an enormously destructive force.

It only takes 15 centimeters of floodwater

to knock a person off their feet.

A flood’s destructive power can be quick and unpredictable,

giving people little or no time

to escape from its ruinous path.

In this episode of Deadly Disasters,

we’ll focus on one of the worst floods

ever to occur in America,

following the breach of levees along the Mississippi,

which unleashed a torrent of water,

causing death and destruction over a vast area.

We’ll also focus on two other recent disasters

such as the floods in Germany,

when two of the largest rivers in Europe

burst their banks,

and a terrifying overflow in New York,

where more than 400,000 of its residents

were put at risk of inundation.

You would imagine that hurricanes, tornadoes

and earthquakes might be the most dangerous and deadly

of all the natural disasters,

but you would be wrong.

Flooding causes more deaths worldwide

than any other disaster, apart from famine.

They can occur in a number of ways.

As water falls to the ground,

it will seep away into the soil.

But if it falls faster than the ground can absorb it,

there will be a risk of flooding.

One of the biggest changes that we’ve seen,

in terms of flood risk,

has been because of the way we’ve managed our landscape.

We now have a lot of concrete areas,

which means that if it rains, it’s going to run off

really, really quickly to the river,

and we’re going to get those high flood peaks.

So when we change our landscape in this way,

we can’t use that landscape

as a natural defense against floods anymore.

It won’t soak up that rainwater like a sponge.

Instead, it will cause the water to run off

really quickly to the river.

Water will pose a risk

to life and property

as it travels downhill through channels,

such as streams or rivers,

which can turn into deadly torrents.

Cities contain systems and infrastructure

to transport rainwater

into appropriate basins and reservoirs.

Usually, the infrastructure does its job,

and you never have to think about where the rain goes

when it runs off.

The problem with the drainage system is dimension.

The dimension of the draining system is usually very low.

It’s built to get rid

of the normal rainfall in a normal year.

And if you have extreme rainfall,

you have too much rain for the drainage system,

and you get the urban flooding problem.

Because the water

can’t drain fast enough,

it will begin to rise, sometimes into homes.

If the water drainage for the city discharges into a river,

this can also cause flooding.

There are many different ways in which flooding can occur.

Overbank flooding happens when too much water from rain,

or the melting of ice,

tries to flow down a natural course like a river.

Unusually heavy rain,

or snow melt near the source of a river,

can lead to vast amounts of water

flooding into the wide-reaching network of brooks,

small streams and tributaries that feed into the river.

In this way, a huge amount of water from a large area

is delivered to the single channel of a river.

When the amount of water reaches a critical level,

the banks, or the natural flood plains,

can no longer contain the water spilling over.

This often occurs at the lower reaches of a river,

which may be densely populated,

causing extensive damage.

In mountainous regions,

where streams tumble down steep hills,

water that overflows will move rapidly down the hillside,

causing more violent damage,

as it finds its way to level ground.

Most floods take hours or even days to develop.

Excess water from rain or melting ice builds up slowly,

and any people living in the danger zone

are given time to prepare

and take evasive action or evacuate.

The level of the water was about-- What? Knee deep?

And that’s when we had realized

that the water wasn’t going to stop rising.

It was either stay or get out.

And we weren’t gonna risk it,

so we got out as quickly as possible.

But that is not always the case.

A flash flood event

can occur so quickly after the trigger event

that there is little or no warning.

In 40 minutes, it was all flooded.

Really, in 40 minutes.

I mean, it just arrived and then you see the power of nature.

When this kind of thing happens,

what else can I do?

Can you stay home? No, you can’t.

You just have to go out and just help whatever you can.

Floodwater will rise quickly

and move rapidly,

instantly turning a babbling brook

into a thundering wall of water

and sweeping everything in its path downstream.

I can’t get to the bridge.

The local area’s all flooded,

so there’s no way of me getting there, at the minute.

The coastline at the edge of a large body of water

is particularly vulnerable to flooding

brought on by waves and storm surges.

Storm surges are when you get a raised sea level,

and that is because you have a low pressure,

from the storm itself, pulling the water up.

But you also get a winds blowing the water against the coast,

and wave overtopping.

We’ve never seen anything like this. No?

The waves are triple the size of a human being.

This kind of coastal flooding is associated with hurricanes,

tornadoes, storms and tsunamis.

When these disastrous events move from water to land,

this can create a surge of water

that smashes onto the coast,

sometimes traveling many kilometers inland.

It is worth noting, that the winds in a hurricane

only account for one out of every 10 deaths,

the rest are caused by the flooding from storm surges.

Waves caused by storm winds are also highly destructive,

but probably the most devastating coastal floods

are caused by tsunamis.

These occur when major disasters,

such as earthquakes or heavy coastal rock or ice fall,

cause enormous disturbances out at sea.

This turns into huge waves,

which can travel across vast expanses of ocean

at high speeds.

The waves, which can reach heights of 10 meters or more

when they reach shallow coastal water,

cause terrible devastation when they smash onto land.

The sheer amount of water contained in a tsunami

means that these types of floods

cause enormous loss of life and destruction of property,

reaching many kilometers inland.

More than 230,000 people lost their lives

as a result of a tsunami

that struck southeast Asia in 2004.

It was one of the deadliest disasters of modern times.

In 2011, a tsunami that struck Japan

killed more than 16,000 people

and caused a nuclear power station

to go into meltdown.

Coastal flooding is hugely destructive

and does some 3 trillion U.S. dollars in damage worldwide.

Another kind of flooding

occurs when the nature of a hillside changes.

Vegetation on slopes can help slow the runoff of water

long enough for it to soak into the ground

or find suitable channels to drain

away from the hill without flooding.

But following a drought,

and particularly after a wildfire,

the loss of vegetation and the hard-baked ground

will leave the hillside vulnerable

to allow excess rainwater runoff.

What you have is a landscape that’s full of sediment,

and it’s also got nothing

to hold back the water when it rains.

So then you get all the rainwater

picking up all of the debris from the fire,

or the sediment from the soil that’s been under drought,

and that’s all carried down into the river,

which can be very destructive in the flooding.

A bout of exceptionally heavy rain

can quickly result in a flash flood.

Deforestation can also create a major flood risk.

So deforestation is very worrying

in terms of how the landscape manages the floodwater.

So we don’t have any trees anymore.

They’re not able to trap the water.

So the water will just run straight off the landscape.

It also means that the water doesn’t soak into the soil,

because those roots aren’t keeping the soil

very porous anymore.

So again, it increases the runoff to the channel.

So our floods get worse where we get deforestation.

A hillside that has had

its trees cut down for wood production

or to clear land for building and farming

is also much more liable to flooding.

Another type of flooding is caused by snow melt.

After a winter of particularly heavy snowfall,

a sudden thaw in mountainous areas

can lead to dangerous volumes of water

draining from the slopes.

This effect can cause similar damage to heavy rainfall.

Extreme rainfall is any rainfall that is unexpectedly heavy,

or we get so much rain over a period of time

that we weren’t expecting that.

A dramatic temperature increase

after a particularly cold winter

can cause ice and snow to melt very quickly

and overwhelm the rivers in the valley below.

When a body of frozen water melts,

a mixture of water and chunks of ice may flow downhill.

Many communities living in valleys

below very high mountains,

like the Himalayas and the Andes,

face the threat of a particularly terrifying

kind of flood: the glacial outburst.

Glacial outburst floods are very sudden,

and they are very large, indeed.

So we can have, for example, an earthquake.

That means that we get a sudden avalanche into a lake

that’s in the front of the glacier,

and that can mean, suddenly,

we have a great pressure on the moraine

at the end of this lake, which can burst very suddenly.

And all of that water will rapidly go down the valley.

They can also be knocked loose by rockfall,

or even an avalanche.

This poses a real danger to the mountain communities.

As the glaciers continue to melt,

more than 150,000 people who live downstream

of these lakes are living in constant danger.

Human interference in the natural course of a river

can also lead to flooding.

Often landowners further up a stretch of a river

may build dams to protect their farmland.

But during a period of high rainfall,

the water that would have

naturally flooded over their land

is, instead, sent downriver,

where it can have catastrophic effects

on communities built in previously flood-free areas.

If water can be so dangerous,

why do so many people choose to live so close to it?

Since prehistoric times,

people have lived by the seas and rivers.

They are a source of food and give access to transport

and trading routes.

The land around rivers also provides

highly fertile flood plains to grow crops.

It should be remembered that flooding

is a part of a natural cycle,

which has sustained humans for millennia.

The silt that is left behind when the floods recede

are rich in the nutrients needed to grow crops.

In more recent times, people have built homes

on picturesque coastlines and river valleys

because they are attractive places to settle.

And as the population rises

and pressure for land increases,

developers have built on reclaimed land,

aggravating the problem, by removing the wetlands

which would have acted as a natural buffer

against flooding.

So when we reclaim land from the sea,

we have to keep the water level lower under the ground.

And that means we have to pump it all the time,

and we have to drain it all the time.

And we have to just keep managing it,

and keep managing it,

otherwise, the sea will come back.

When a river overruns its banks,

or the sea drives inland,

structures not adequately equipped

to withstand the force of the water

are easily destroyed.

Water can push soil underneath a building’s foundations,

causing it to crack or topple.

One of the most dangerous things that people do during a flood

is they try and drive through it.

And it only takes about 30 centimeters,

which is about 6 inches,

of floodwater to sweep the car away.

And people die from this every year,

by trying to drive through it.

Now, you can imagine trying to walk through a flood,

and it does depend how fast the water is flowing.

But generally, you really should not be walking through a flood.

I was swimming.

I had my little daughter in one arm,

and I’m paddling with the other,

going with the current,

trying to stay away from debris and houses

and whatever that were piled up over here.

When the waters finally recede,

they leave the affected areas covered in silt and mud.

The water and the landscape may be polluted

with hazardous materials, sharp debris,

toxic pesticides, fuel and untreated sewage.

Drinking water may be contaminated,

leading to outbreaks of deadly waterborne diseases,

like cholera, typhoid and hepatitis A.

We had as much as 15 feet of water here.

So anyone who lived from here towards the gulf,

their houses were completely underwater, destroyed.

They had no medicine for their heart, blood pressure, diabetes.

To defend against flooding in at-risk areas,

massive efforts have to be made.

Hugely ambitious engineering projects

attempt to stop floodwaters,

or redirect them away from communities.

One of the places built on reclaimed land

which illustrates this perfectly is New Orleans.

An extensive levee system,

coupled with a network of pumps,

attempted to protect the city,

but failed with deadly consequences,

when it was hit by the storm surge

accompanying Hurricane Katrina in 2005.

So on one hand, levees protect people.

That’s what they are made for.

But we also see that if we have a levee,

then the floodplain is disconnected from the river.

The floodwater cannot spread across the floodplain.

And this may increase the risk, or the hazard,

for the people who are living downstream.

So when you put up levees,

it means that you are creating a channel,

which means that if you get rainwater

going towards that channel,

it will rise much, much more quickly,

because there’s no room anymore

for the water to spread out onto its natural floodplain.

So, what you have actually done is channelized all that water,

and it will run quicker.

It will run with more power,

and that can actually cause more damage

in certain circumstances.

In the Netherlands,

where 50 percent of the country

is either below or very close to sea level,

they have built a flood protection system

designed to the point

where the chance of failure in any given year

is roughly one in 10,000.

The Dutch have said, "We have to protect

against the one in 10,000 chance of a flood from the sea."

Whereas New Orleans,

it’s unlikely to be more than one in 200.

So a much higher standard in protection in the Netherlands,

but obviously, at a much higher cost.

After a disastrous flood in 1953 that killed 1800 people,

the Dutch built huge dams

to supplement the 22,000 kilometers of dikes.

There was a total commitment to keeping the water out.

People usually believe that they are protected from a dike,

but usually, it’s just a problem

of the magnitude of the flood event.

There’s always a flood event which is bigger than the dikes,

or the levees.

And, um, there’s always a residual risk,

even if there are dikes,

so it’s never a good idea to construct buildings

in areas which have a flood hazard.

Cities now use parks and public spaces

as emergency reservoirs for the floodwaters

generated by severe rainfall.

They also use highly advanced computer modeling

to predict with extraordinary accuracy

where and when floods will occur

and how severe they are likely to be.

So when we’re predicting floods,

we use computer models of the Earth’s system.

So we take in the rain that’s coming from the atmosphere,

and then we get that falling onto the land.

And we use the physics of the land’s surface

to work out where the water is going to go,

and how it gets to the river.

And then how much water will be in the river.

When we think about flooding,

we think about how big that flood event will be.

Sometimes, those floods happen quite often,

but they’re quite small.

Other floods will be much, much bigger,

and they will happen more rarely.

So we try and work out whether it’s going to be a big,

but rarer flood,

or it’s going to be a small,

and one that happens quite often, flood.

Many scientists define certain rare

and extremely destructive floods

as "one-hundred-year floods."

The term "one-hundred-year flood" is extremely unhelpful,

because it gives the impression

that you’re going to get a flood every 100 years.

But it just doesn’t work like that.

It’s worked out over a very long period of time,

and it means that on average, every 100 years,

you would get this flood.

But that could mean that you’d get flooding

in two consecutive years.

So it really is a very unhelpful term.

It’s more helpful, I suppose, to think about it

in terms of how likely it’s going to happen.

So we might get a "one-hundred-year flood"

happening next week,

and then we might get one the following year.

So we are definitely seeing that extreme rainfall

is becoming more frequent

and more heavy in different places in the world.

And that’s very worrying.

Of course, it means that if it’s raining more heavily,

we’re going to get more water running off to the river,

and an increased flood risk.

To count as extreme rainfall,

there must be more rain in a day

than the top 1 percent of daily rainfall

throughout the total period being studied.

These sudden bursts of rain

put severe strain on the man-made features

designed to control water.

Drains overflow. Dams burst.

Levees get breached.

So it is no wonder

that with up to 50 percent heavier downpours,

we are going to see more flooding.

Extreme rainfall that leads to flooding

can be a lot of rainfall falling very, very quickly.

Or it can be: It’s raining, and raining, and raining,

several storms passing over in a couple of weeks,

which just then will cause the flood.

One of the worst floods

in the history of the United States

occurred in 2011, along the Mississippi river.

The extraordinary flooding was blamed on heavy snow melts,

three large rainstorms, and tornadoes earlier in April.

These events also triggered flooding from the Ohio River,

which added to the mass of water

flowing into the Mississippi.

Thousands of square kilometers

of agricultural and residential land

were engulfed by water that cascaded over the banks

of the Mississippi River.

There were areas deliberately flooded

when levees were blasted, and spillways opened

to divert water away from large settlements.

This was, by no means, the first time

the mighty river had flooded.

The 1993 Mississippi flood

was the costliest U.S. flood of the last century,

responsible for about 15 to 20 billion U.S. dollars

in economic losses.

More than 600,000 square kilometers

in nine states were flooded.

Knowledge gained from this previous disaster

led the federal government to construct

numerous levees and spillways

to contain and channel floodwaters.

This meant that in 2011,

the path of the torrent was, to a certain extent,

predictable and controllable.

It’s very difficult to get the balance right

between protecting pieces of land with levees

and having this problem that the levees might fail,

under certain circumstances.

So if there’s enough water,

they will be overtopped.

And sometimes, they will fail

because there’s always this leftover risk

when you try and put up these defenses.

You could build them as high as you like,

and there would still be the chance that they might fail,

under certain circumstances.

So one of the interesting things about levees,

is there is something called "the levee effect,"

which means that people feel safer when a levee is built.

And that means they often move into the area behind the levee,

and then, actually, the flood risk is greater,

because those people are there in that area.

And should the levee be overtopped, or fail,

then there will be quite substantial damage

and possibly, loss of life.

To understand why the Mississippi

is such a dangerous river,

you need to look at its geography.

The Mississippi basin has a wide top

that stretches from Montana and southern Canada in the west

to New York state in the east.

The river then curls south for more than 3700 kilometers

through the United States,

emptying into the Gulf of Mexico.

The river and its tributaries touch parts of 31 states.

Problems with flooding occur on the Mississippi

because it gathers water from such a vast area.

Its watershed is the fourth largest on the planet,

covering a 3.2 million square kilometer expanse

across 31 states.

Because of their abundant network

of roughly 250 tributaries,

water from rain and melted snow

can travel to the river

from surprisingly great distances,

in some cases, as far away

as the Rocky Mountains in the west.

Rain that falls in the Dakotas

right up on the border with Canada in the north

will eventually travel down the Mississippi

all the way to the Gulf of Mexico in the south.

Throughout the spring of 2011,

the U.S. Army Corps of Engineers

monitored both the coming of floodwaters

and the dangers faced by the population

living on or near the bank of the Mississippi.

Although huge efforts were made to control the flooding,

nothing could be done to stop it.

The disaster unfolded gradually,

day by terrifying day,

as the cresting of floodwater, slowly but steadily,

made its way southwards

down the length of the mighty river.

It breached levees in Missouri,

Arkansas, Mississippi and Tennessee,

leading to the destruction of property,

the evacuation of many thousands of residents,

and several deaths.

Louisiana governor Bobby Jindal

declared a state of emergency,

expected to extend for a month.

He later requested the assistance

of 1500 National Guardsman

to prepare for an opening of the Morganza Spillway,

in order to shift potentially devastating flood waters

away from the highly built-up areas.

The rising Mississippi river

welled over into downtown Memphis streets

and threatened homes on Mud Island,

a community of about 5000 residents

connected to downtown Memphis by a bridge and causeway.

Concerns were growing that the levees might be breached

in the Louisiana cities of Baton Rouge and New Orleans.

This would have displaced many thousands of people

and shut down a network of petroleum refineries

responsible for a large part of American petrol production.

On the 3rd of May,

U.S. President Barack Obama

declared flood-damaged areas of Tennessee

a federal disaster zone

as the Mississippi River crested there.

Officials downstream in Louisiana

began evacuating inmates

from the Louisiana State Penitentiary in Angola.

the largest maximum-security prison

in the whole of the United States.

The U.S. Army Corps of Engineers

warned that if the pressure of floodwaters on the Mississippi

was not relieved by opening spillways,

New Orleans could be flooded by 6 meters of water.

In order to save Baton Rouge,

the Morganza Spillway was partially opened

on the 14th of May.

This was the first time this had occurred since 1973.

More channels reopened in the following days.

Opening the Morganza Spillway

released 17,000 cubic meters of water per second,

nearly 2.8 times more than the Bonnet Carre Spillway,

which had been opened further north.

But unlike that spillway,

opening the Morganza would cause flooding

throughout rural communities near the Atchafalaya Basin,

into which the spillway would be emptied.

As a result of the spillway opening,

a rush of water headed south.

The waters deliberately released from the Mississippi

drained into the Atchafalaya River basin,

covering a vast majority of its cropland.

In the state’s French Louisiana region,

homes and local farmland

were sunk below 3 to 6 meters of water.

In the later weeks of May, the Mississippi River

had reached record levels in many areas,

but was now, thankfully, beginning to recede.

State officials began the process of checking properties

that had been evacuated to see if they were safe to live in.

Many of the buildings were condemned

or would require complete reconstruction.

Chemicals from floodwater that entered the Gulf of Mexico

led to an increase in algae blooms

that deoxygenated the water

and severely affected fisheries already suffering

because of the effects of the Deepwater Horizon oil spill

of 2010.

The Army Corps of Engineers

estimated it would cost 1 billion U.S. dollars

to repair the damage caused by the flood.

Congress allocated 802 million U.S. dollars

to the U.S. Army Corps

to locate and restore

the most vulnerable areas of flood defenses.

I feel more secure since they done raised the levees.

And at first, they wasn’t prepared for what happened.

But now, I think they’re more prepared.

Despite all of its advanced flood defenses,

the river systems of America are still likely to overflow.

But it isn’t only the mighty rivers of the United States

that are vulnerable to flooding.

Europe has the Danube,

the Loire and the Rhine.

There is also the Elbe, which runs all the way

from the mountains of the Czech Republic to the North Sea.

When it burst its banks in 2013,

it carried floodwaters right through Germany,

killing 25 people

and racking up 3 billion Euros’ worth of damage.

Southern and eastern Germany were particularly affected.

But several other countries were also hit by floods--

Austria, Switzerland, Poland, Hungary, Slovakia,

Croatia and Serbia were all touched by a disaster

that reached right across central Europe.

We came here to protect from Duna.

The water is very high,

so we have to make sandbags

to protect us from the water.

So I hope it will be okay.

The June 2013 flood

was the most severe large-scale flood

to strike Germany in at least six decades.

Many flood gauges along the Elbe and Danube rivers

showed record water levels.

The flood severity index,

a measure which combines both the flood’s magnitude

and the area affected,

is almost twice as large for this event

as the index for the previous floods of August 2002.

At that time, it was the most

expensive natural disaster for Germany.

The month when the flood occurred, in May,

was unusually wet.

We had a lot of rainfall before the event started.

In some regions, it was twice as much

as the mean monthly rainfall.

And then, at the end of May,

there was a period of two to three days

where we had another period of extreme rainfall.

And this rain fell on soils which were already saturated.

Then the water cannot infiltrate.

It runs across the surface to the river,

and causes, of course, a flood.

And that’s it.

So it was caused by a very strong pre-event rainfall,

and then there was a storm event,

and the soils were already saturated.

Almost all the rivers in Germany

showed high water levels,

with especially severe flooding

occurring along the Danube and Elbe rivers.

Warm and moist air masses were continuously drawn in

from the sub-tropics in the south

towards northern and central Europe.

Several low-pressure systems,

which swept in one after the other,

brought about long periods

of widespread and intense rainfall.

We have to consider that the last big event, in 2002,

came after a period of, let’s say, 100 years,

where there was no major flood at the Elbe basin.

There was not so much investment in flood protection.

After the flood event of 2002, many things were done--

Information systems were improved.

Early warning systems were improved.

The measurement systems, the gauge system, was improved.

There were management plans for river basins,

for parts of the Elbe basin,

and there were some technical measures,

which were planned already.

Dikes were improved.

They also restored many old dikes.

And these restored old dikes,

they worked quite well when the flood in 2013 came.

In 2002, we had a lot of dike breaks

because the dikes were not managed very well.

But after these 11 years between both events,

many dikes were enforced.

And these dikes worked very well.

Breaking dikes, in 2013,

appeared only in areas where they were not restored yet.

The most intense rainfall

occurred between the 31st of May and the 4th of June

over a huge area of saturated ground,

covering most parts of southern and eastern Germany,

and in particular,

the catchments of the Danube and Elbe.

There was so much water in the Rhine

that parts of it had become too dangerous for shipping.

Swathes of suburban Prague were left under water

after the Vltava River burst its banks.

This was bad news for German towns further north,

as the surging Vltava would carry its floodwaters

all the way to the point where it merged with the Elbe.

Thanks to strong metal barricades

securing Prague’s historic city center,

the waters shifted north towards Germany.

The Elbe rose to alarming levels in Saxony,

as water moved in from the Czech Republic.

Passau, a German city on the Austrian border,

was also now under threat.

Passau is often called "the city of three rivers,"

because of its position at a point where the Danube,

Inn and Ilz rivers all intersect.

But that location proved the city’s undoing

when its river hit a record water level of 12.75 meters--

The highest since a historical flood of 1501.

When the inevitable happened, and the river burst its banks,

whole areas of the city disappeared underwater.

The streets looked more like canals.

In the area around the city of Leipzig,

Saxony’s most populous city,

some 6000 people had to be evacuated.

In the Bavarian city of Deggendorf,

located on the river Danube,

the levees burst on the 5th of June,

allowing torrents of water to flow into the city.

In Dresden, one of the main bridges across the river

had to be shut off to traffic.

Wide areas were flooded,

but the historic parts of the city were spared.

People had worked frantically to shore up defenses

as the river peaked at nearly nine meters,

7 meters above its normal level.

Thousands of emergency personnel and residents

had worked through the night

to fill up sandbags

and build up flood barriers.

Next to be hit were the cities of Bitterfeld and Halle.

Chancellor Angela Merkel visited Bitterfeld

on the 6th of June and promised further emergency aid.

Throughout Germany,

60,000 local emergency personnel and aid workers

were deployed to battle the floods,

as well as 25,000 federal disaster responders

and 16,000 soldiers.

Deggendorf was stricken by a third levee break,

with floodwaters pouring into entire neighborhoods.

Many homes remained underwater,

and authorities warned that the dam holding back the water

was in a deeply precarious state.

In East Germany,

about 23,000 Magdeburg residents

were forced to evacuate after a dam failure occurred

on the flood-swollen Elbe.

Further along the Elbe,

hundreds of people were evacuated from their homes

in the towns of Stendal and Aken.

Authorities demanded that 150 people evacuate.

In total, 45,000 people

were told to abandon their homes in Saxony-Anhalt,

as the state bore the brunt of the swollen Elbe.

It’s a difficult thing to tell these people

that they can’t live there anymore.

If you live somewhere for 30 to 40 years,

something like that, try to imagine to tell such people:

"So you have to go, you have to live somewhere else.

You can’t do this." And so it’s...

The theory is very good,

not to build anymore in areas which are affected by flooding,

but in practice, this faces quite a lot of challenges.

Fischbeck, a 700-person village in the district in Stendal,

experienced a total inundation

following the breach of a nearby river dike.

There are two very dangerous things:

The ones in the lowlands

where there’s widespread inundation of areas,

which causes lots of damage.

And in addition to that,

which is even more dangerous, if a dike breaks.

People who are believed to be protected from the dike.

And the second problem is in the mountain areas,

where the floodwater comes from.

And you have very, very short early warning times

and very rapid increase of the water levels in the rivers.

And the flood rushes through the valleys.

And that’s quite dangerous in the mountain areas.

Two Army helicopters were then deployed

to drop giant sandbags on the gap in the flood defenses,

but their efforts to repair the dike failed.

Around 700 soldiers worked to build a dam of sandbags

to protect a power substation

in the badly hit area of Rothensee,

in a bid to stop the electricity from failing.

Train travelers faced severe delays and cancelations

when a railway bridge

on the line between Berlin and Cologne,

Frankfurt and Amsterdam had to be closed.

More than 52,000 people had to be evacuated

during the June 2013 floods.

The total number of fatalities

in all of central Europe was 19.

The German Farmers’ Association

estimated that 2500 square kilometers of grasslands

and crop fields were flooded.

Large industrial companies,

like the car manufacturers Porsche in Leipzig

and Volkswagen in Zwickow,

as well as Südzucker in Zeitz,

the largest sugar producer in Europe,

had to stop their production due to direct flood effects,

or the indirect effects

of disruption to their supply chains.

Although there had been many lessons

learned from the catastrophic flooding

that had occurred 10 years before in 2003,

some towns were better prepared than others

when the waters rose again.

The town of Grimma, for example,

started to build a defense wall in 2007,

but it was half finished and then delayed.

The completion of that wall

might have prevented their second flood

in just over 10 years.

Dresden, on the other hand, was one of the success stories.

By the time the 2013 floods hit,

its overall communications apparatus

was used effectively to protect vast parts of the city.

Both the new mobile and older stationary protection walls

did their jobs successfully.

And for the catchment area of the Weiseritz River,

there were proper runoff pathways,

all of which avoided severe consequences for Dresden.

So the Elbe flooding triggered a rethink, I suppose,

about how we work together as a community

to help people in areas at flood risk.

And one of the things you can do

is provide an earlier warning of things that are gonna happen.

The European Commission has set up a new flood forecasting

and early warning system to help give an early warning

to the community in Europe when a large event is coming.

So that can tell you, maybe, 15 days ahead

that a large event is coming.

It can also help European countries work together

to get equipment in the right place,

at the right time.

It’s a terrifying prospect

when flooding threatens to overwhelm a tightly packed,

densely populated urban environment.

And there can be few places in the world

that fit that description better than New York City.

In the autumn of 2012, both the city

and virtually all of America’s Eastern seaboard

were pummeled by Storm Sandy,

the deadliest and most destructive hurricane

of that year’s Atlantic season.

Fifty million people were impacted by the storm,

with roughly a million instructed

to evacuate their homes.

We gotta get out, it’s imperative.

At this point, it was just, like, a matter of just sanity.

We got no hot water, no electricity.

This was unprecedented.

The damage done here, I couldn’t have imagined.

In New York City, 43 people were killed,

many from drowning in the floods

the day before the storm made landfall.

New York’s Metropolitan Transportation Authority

closed the nation’s largest transit system.

Subway and commuter rail services

were suspended at 7 p.m.,

and bus services at 9 p.m.

Governor Andrew Cuomo mobilized the National Guard,

while New York City Mayor Michael Bloomberg

ordered evacuations in all low-lying areas,

as well as the closure of public schools.

More than 70 evacuation shelters

were open around the city

in readiness for the imminent disaster.

This one put fear in my heart.

And I think everybody else felt the same way.

It’s unbelievable...

Sorry.

There are not even words to describe it.

I mean, it’s absolutely insane.

The water was moving by three feet every four minutes.

The storm first struck the coast of southern New Jersey

with a storm surge inundating the beachfront neighborhood

of Breezy Point,

causing hazardous electrical short circuiting

that burned 110 homes to the ground.

We haven’t seen a storm like this in about 30 years--

The last time it was like this, and it wasn’t this bad.

More than 190 firefighters

battled the blazes for hours into the night.

They were still putting out flames

more than nine hours

after this nightmare first began.

Floodwaters rushed down

New York’s 108-year-old subway system,

flooding seven major tunnels.

Seawater flooded into the Battery Tunnel,

cutting off the city from Long Island.

And the Holland Tunnel,

connecting New York City to New Jersey,

was gorged with floodwater.

I’ve never seen anything like it.

I think it’s the worst storm, they say, since 1938.

There’s not going to be transit for a while.

There’s not going to be power for I don’t know how long.

That’s the major thing is the power

because we live in a high rise,

so there’s no way up and down except to walk the steps.

We don’t know what to expect.

How long it’s going to last. How bad it is.

And how it’s going to get back to normal. No idea.

Power was lost in some 500,000 homes,

plunging Lower Manhattan into darkness.

The overwhelming surge

left much of New Jersey’s Atlantic City underwater,

leading 30,000 residents to evacuate.

There were eight drownings on Staten Island,

occurring within eight blocks of one another.

It was the highest concentration of deaths

attributable to the storm in the United States.

In Hoboken, across the Hudson from New York City,

Mayor Dawn Zimmer warned that live wires were dangling

in standing water,

which was becoming contaminated with sewage.

The National Guard evacuated deluged homeowners

and distributed meals.

U.S. President Barack Obama

and New Jersey Governor Chris Christie

toured the state of New Jersey

to survey the devastation two days after the huge storm.

In the immediate aftermath,

centers were set up on Coney Island,

the Rockaways and parts of Staten Island

so that meals and bottles of water could be distributed.

As the floodwaters receded,

New York began the long road to recovery.

The cleanup operation ran 24 hours a day,

as fleets of several hundred trucks,

river barges and tugboats

moved an estimated 3 million cubic meters of debris

to landfills in upstate New York and Pennsylvania.

Flood management is a very, very, very wide field.

On one hand, you have technical measures, like dikes,

or retention basins, or dams.

But as an experience from the last, let’s say,

20 to 30 years, we know

that technical protection is not enough.

We can protect to some degree,

but there’s no full protection. It’s not possible.

We can manage flood events, to some degree,

and this management includes even much more

than just technical measures.

It also includes the nature of water retention,

to keep the rainwater in the headwater areas,

where it comes from. Where the flood is generated.

It also includes a lot of precaution.

People are informed that they know what to do,

what they have to do.

And the buildings are constructed in the right way

to withstand flood events.

People have their own financial resources

to deal with a flood event, with damage.

Um, there’s a lot of things

which can be done for flood management.

It’s very difficult to work out

whether floods are occurring more frequently

because they are very, very variable.

So we might get a flood-rich period of a couple of decades,

and then it might be drier for a couple of decades.

But over time, I think we are seeing

a more serious flooding happening.

We have got records going back several hundred years,

in places in the world.

And so it does seem like we’re getting these bigger events

happening more often.

If you’re aware of when it’s going to flood,

or at least what your flood risk is,

then you can make yourself resilient to floods.

So you can build back better.

You can make your house flood proof.

You can think about how you design your city,

so that there is room for the water.

So although we live in areas that are at risk of flooding,

we can do something about it to make our lives better,

when it does flood.

One of the most important things that we can do

to be prepared for floods

is to understand how the landscape works.

So to really appreciate the fact

that we need to store our flood water somewhere...

We can’t just magic it away.

We have seen that floods can strike virtually everywhere.

From the picturesque river towns

of southern Germany,

to the urban powerhouse of Manhattan.

From mountaintop communities high in the Himalayas,

to the cornfields of the Mississippi Delta,

it would seem that few places on Earth are safe

from one of Mother Nature’s most immense deadly disasters.