Original subtitles

We live on a water planet,

with 71% of the Earth’s surface covered in water.

Only 2.5% of the Earth’s water is fresh water...

held in the ice caps,

lakes...

rivers...

clouds and streams.

We need water for life,

to drink and irrigate crops.

Not enough water,

and the land withers under drought.

However, too much water can be just as deadly.

When normally dry land overflows with water,

you get flooding...

a natural occurrence,

sometimes benign and sometimes catastrophic.

When we have very, very big flood events,

there’s not a lot you can do to get out of the way.

Floods exist in the present and are part of our history,

featuring in the legends we use to make sense of the world.

Floods are among the most costly natural disasters,

affecting the largest populations of people

with far-ranging consequences,

including damage to property,

disease and loss of life.

In this Deadly Disasters,

we will look at the different types of flooding

and investigate the reasons why they occur.

Our experts will look at some

of the most catastrophic floods

of recent years.

We will consider

how different countries manage flooding,

particularly in the developing world,

where resources can be stretched thin.

Eyewitness reports will tell the human story of flooding

and the personal toll these events take.

Flood-prone areas

can also tend to be highly populated.

Low-lying flood plains adjacent to rivers attract people.

The flat land is easier to build on.

Proximity to the river is good for farming and irrigation.

Rivers allow for people

and supplies to be transported,

and previous floods provide nutrients that farmers need.

The human impact of floods can be catastrophic

when they hit in areas of dense population.

By the time people got back to their homes,

there were no homes anymore.

Floods kill more people each year

than any other form of extreme weather.

The cost of flood damage is astronomical,

up to 40 billion U.S. dollars per year in the U.S. alone.

Water is part of the landscape,

collecting in ponds and lakes on the surface

and as aquifers and groundwater below.

Rivers and streams collect water

and move it downhill, eventually back to the sea.

In normal circumstances, the geography of most locations

prevents extreme floods from occurring.

Water drains into the soil,

runs into the rivers

and is carried away eventually to the sea.

Water is also intercepted by plants,

and some of it evaporates.

The landscape is efficient at moving it from the surface

via streams and rivers to the sea

or allows it to slowly soak into groundwater.

Floods happen when water is added to a landscape

quicker than it can be carried away...

when the surface becomes waterlogged

and the flow of water exceeds what can be carried away.

Floods occur when water remains in areas not used to water.

This excess water can come from precipitation,

coastal storm surges

and meltwater and runoff from higher ground.

Flooding can be small and localized,

presenting minimal danger to local populations.

In extreme circumstances,

floods can cover huge areas,

many thousands of square kilometers

for weeks at a time,

causing life-changing consequences

for the people affected.

Even six inches of water, or 15 centimeters,

is enough to knock a person off their feet.

And even 30 centimeters,

or a foot, of water can move cars.

And so when you have a flood event

that can be several meters deep,

that can actually force people to the roofs

and need immediate evacuation.

Coastal areas present a particular flood risk.

Large areas of low-lying land risk sea flooding

from storm surges and precipitation.

Areas close to the sea

often receive more rainfall than inland.

In the U.S., this can be due

to atmospheric rivers.

Conventional land rivers are a place

where water accumulates

and flows in the same direction,

taking advantage of the geography

to concentrate flow in troughs and gullies

to carry water quickly across the land.

Atmospheric rivers that form in the sky

do the same thing but with water vapor.

Long, thin areas with high moisture content

transport water thousands of kilometers across the globe.

Often fed by water evaporation in warm Pacific waters,

atmospheric rivers are responsible

for much of the rainfall in North America.

Carried on fast winds,

the water vapor remains locked in the atmosphere

like a saturated sponge

until something comes along to squeeze it out.

That can be the edge of a continent

forcing water out of the air

and triggering torrential rainfall.

Much of the precipitation in the U.S.A.

is transported by atmospheric rivers.

Coastal areas often bear the brunt of storms.

Large waves can develop over large distances

and then release all this built-up energy

onto the land as a storm surge.

A storm surge is when you have a raise in the ocean level

because of low pressure in the atmosphere.

And that’s compounded with wind that’s blowing the water

from the sea onto the land.

So you get this kind of surge in water,

which means you can get floods further inland

than you would with just a high tide.

Extreme storm surges

can overcome flood defenses and drive water inland.

In the United States,

one of the biggest surges

was caused by Hurricane Katrina in August of 2005...

resulting in water levels

of eight meters above high tide.

Hurricanes pick up a lot of energy and water moisture

from traveling over the ocean and warm waters,

and when they reach landfall,

they can dump a lot of that water onto the land.

When hurricanes make landfall,

bad things usually follow.

The levels of devastation that you see

in these types of events is huge, it’s massive,

and what we see on the TV

when we see pictures of people standing on roofs,

that is just the tip of the iceberg.

Hurricane Harvey was the second most costly hurricane

to hit the U.S. since 1900.

It began as a tropical storm in the Gulf of Mexico

around August 17th, 2017.

When extreme tropical cyclones occur,

like Hurricane Harvey, the amount of rain

that falls from them will be even greater.

It had become a Category 1 hurricane

by the 24th.

By the next day, it was upgraded to Category 4

and en route to Texas.

When Hurricane Harvey tracked over the Gulf of Mexico,

the Gulf of Mexico was actually much warmer than normal.

And so that gave the hurricane itself a lot more energy

and was able to pick up a lot of water.

And so when it made landfall,

it dumped all that water on land.

As the flood bore down on the coast,

flood preparations began.

Aware of the storm and potential floods to follow,

the citizens of Houston prepared.

Forty-one thousand emergency shelter beds

were made available

and 200 buses put on standby

to move people inland from the worst-hit areas.

In the buildup to the landfall,

the Houston mayor, Sylvester Turner, tweeted:

If you choose not to evacuate,

it means that somebody’s going to have to come and rescue you.

The evac horn went off, and they said you have five minutes

to get whatever you can and let’s go.

So we had to climb over the back wall,

we had to walk from the back of that wall

on the back of our house in thigh-high water.

The next morning, it kind of hit me,

I’m like, "Oh, my goodness. I don’t even know

if I have a house or a car, I don’t know."

And I cried for a minute, and then I prayed about it.

There was another lady crying, I went and gave her a hug.

On August the 25th, it makes landfall on San Jose Island

in southern Texas,

with 210-kilometers-per-hour winds

and a massive storm surge.

The next day, the winds calmed

and the event was downgraded to a tropical storm.

Yet, whilst the winds may have abated,

the rain did not let up.

By August the 27th,

Harvey had dropped a year’s worth of rain

on Houston in just five days.

That amount of water falling over a city

or a very built-up area is absolutely devastating.

It’s relentless, and the drainage--

Both the natural and the engineered drainage capacity

just can no longer cope with that amount of rain.

The rainfall was described by many commentators

as an historic amount of rainfall, a 500-year storm.

Harvey was particularly intense

because when it reached landfall, it stalled

and moved very slowly along the coast.

And it was bringing water from the Gulf of Mexico

and dumping it over Houston.

And essentially the storm moved on and off the land

around five times before it dissipated

and moved northwards.

The ability to predict flooding

has a huge impact on how the response is managed.

With enough time, people can be safely evacuated,

emergency services primed and flood defenses shored up.

So there are two main ways

that you can really limit devastation from a flood.

The first one is to be prepared

and to know what to do when a flood is coming.

And the second one is to know where to get warnings from

so that you can hear what the latest information is.

Put simply, sufficient early flood warnings

can actively save the lives of people in high-risk areas.

Early-warning systems are an important tool

to tackle floods.

Flood predicting requires real-time, on-the-ground data,

from rainfall to ground moisture

and knowledge of the landscape.

Flood forecast tools have been developed

to apply rainfall predictions

onto three-dimensional maps of the ground.

By looking at the topography and the ground cover,

water flows can be predicted

and floods can be mapped at street level,

sometimes up to 48 hours in advance.

The University of Loughborough have trialed

this type of flood map system successfully

in four U.K. cities,

with hopes to make an international product soon.

Satellite imaging has been an important component

of weather prediction for some time.

Storms can be tracked and monitored

as they move across the globe,

making it possible to predict when they make landfall.

This satellite data is key in predicting floods,

since being able to estimate the times

and amount of rainfall in an area is key.

NASA scientists have developed satellite capability

even further.

By measuring microwave emissions from the landscape,

it is possible to assess soil moisture.

The Soil Moisture Active Passive system

is able to measure the soil moisture for the entire Earth

in just three days.

Soil moisture is an important data set for flood prediction

because it allows researchers to know

how much rainwater can soak into the land.

A large data set like this,

combined with weather predictions,

increases the ability to make global flood predictions

on a large scale.

If an area is already deemed waterlogged,

then they will be able to know

if the coming rain will bring with it

the risk of flooding.

In Houston, more water was being dumped

than the drainage systems

and natural runoff could cope with.

It had nowhere to go.

It’s never been like this before.

I mean, it’s awful,

but, you know, we’re getting everybody out.

Police and the fire department were here yesterday,

helped us get more out, so we’ve been okay.

With Harvey, people were not really expecting this to happen.

So they weren’t prepared.

So they didn’t take the actions they could have taken

to protect themselves and their property.

Urban areas exacerbate flooding for several reasons.

Flood risk is reduced by vegetation.

Plants intercept and absorb some of the water,

slowing its propagation downhill.

The water is given time to soak into the soil

rather than gather on the surface as a flood.

Urban development reduces the vegetation,

replacing it with concrete, buildings and tarmac.

Modern building materials coat the land

in an impermeable layer,

preventing water from soaking into the ground.

Instead it collects together and starts to pool.

Drainage can only do so much,

and few cities have systems in place

to remove hurricane-levels of water quickly enough.

Good flood infrastructure can prevent cities

from the risk of flooding.

However, even the most sophisticated technology

comes with problems.

We have something called the levee effect.

It’s very common to find people

who live behind very large flood defenses

are actually much less prepared for a flood when it happens

because they’re perceived to have a very high protection level.

But when their protection level is breached,

they’re not prepared.

So you need to know

how high the water is going to get.

You need to listen to those warnings

about what’s going to happen.

You can move things upstairs if that’s a possibility.

You can switch off all electricity.

That’s very, very important to stop fires.

And you can evacuate.

If you really need to, you should go.

Houston was battered by up to 50 inches of rain

in just a few days.

The flooding happened quickly.

We know that there was a problem

with the communications with the Texas floods.

We know that there were some very good warnings

issued 30 hours ahead,

saying there was devastating amounts of rainfall coming,

but some people didn’t seem to receive those warnings

or really know what to do when they received those warnings.

Five people were killed in the initial storm.

If you see the news, everybody’s helping each other.

They forgot about race,

they forgot about what color you are.

More than 135,000 homes were affected by the flooding.

Floods cause terrible devastation

to buildings and property.

The structure of buildings can be damaged.

Furnishings, carpet and plasterboard

become soaked and waterlogged.

A lot of this material has to be ripped out and scrapped

when the waters recede.

Cars and electricals are destroyed.

In addition to homes,

industrial areas are also affected.

Houston is a big player

in the petrochemicals industry,

and toxic chemicals leached into the floodwater.

Elevated levels of chromium, nickel and arsenic

were found in the water,

which are detrimental to people,

animals and sea life.

The effects of floods on people

is just as dramatic.

With fast flows and storm surges,

people risk being washed away,

injured and drowned.

But even slower-rising floods

can present a large risk to human health.

It’s not only the damage that the water actually causes

to buildings and properties,

but it’s also the contaminants it can bring

that even after a flood can cause many diseases.

So cholera, for example.

You having--?

I think he’s having a seizure.

I’ll check on him.

One of the most common misconceptions about flooding

is that nice clean water will be running through your house.

And what’s left behind actually is huge amounts of silt,

disgusting debris, you know, sometimes sewage,

and it can really, really last a long time,

that problem, trying to clear that up.

As people fled the floods,

shelters soon became overburdened

and firefighters began a door-to-door search

to look for trapped survivors.

Elderly and disabled people

who are unable to escape the initial floods

can end up trapped in their own homes.

The rescue efforts took nearly two weeks to complete.

During that time, trapped people risked illness

due to exposure, lack of supplies and disease

spread by flooded sewers.

floodwaters hamper rescue efforts.

The high water levels and sometimes fast-flowing water

mean that often boats and helicopters

are the only way people can be reached.

Everybody around here’s stuck in the house

unless they already left ahead of time, so...

But I came two times, I talked to them over and over,

and they finally came around there and just...

When you get a big city flooding,

it can be very frightening for the people who live there.

Their entire lives are caught up in that city.

There is really nowhere else for them to go.

And they lose electricity, they lose their ability

to walk across the city. They don’t know what to do.

Floods can leave people desperate.

Where do you all live?

It’s really a low-type person that would come in and--

When you this, how devastating it is to your heart,

and knowing people are suffering without insurance,

it’s devastating that someone would wade through water,

through snakes and alligators,

to come and take people’s possessions.

We’re our own police force right now.

So-- And I think all over Houston

people are kind of taking the same stance.

You’ve got an AR-15 here,

we’ve got a .357 semi-auto

and then two 9 millimeter with 5.56 NATO rounds,

so a full metal jacket, you know.

Floodwaters take time to recede,

delaying people’s return home to pick up the sodden pieces.

Homes and furnishings are waterlogged,

and damp and mold has set in,

meaning many of the house’s contents need to be dumped.

Once a flood has just happened,

people view their homes very differently.

This is the place they felt most safe.

And now it’s just been devastated by flood.

So it’s very difficult for them to come back to that

and feel safe again.

People have to start again.

Rebuilding can take years.

People expect governments to protect them from all floods,

and this is quite problematic

because that’s completely impossible.

We don’t know when the next major flood

is going to happen in Texas

and if it will be on a similar scale to Harvey.

Hopefully lessons have been learned from 2017

and can be applied to help save lives

next time the flood comes.

Storm surges are inevitable,

and it’s impractical to fully mitigate the risk

with flood defenses.

World coastlines are much too long

to physically protect with barriers and levees.

The quantity and intensity of storm surges

are influenced by the tides and level of the sea.

Most of the earth’s fresh water is stored as ice

in the Arctic and Antarctic ice shelves.

The Antarctic ice sheet alone

covers an area of almost 14 million square kilometers

and contains 30 million cubic kilometers of ice.

During the summer, the ice recedes,

adding meltwater to the ocean.

In recent years, the quantity of ice

melted at the poles has increased.

The change to the world’s climate

has resulted in a warmer planet,

and if temperatures continue to rise,

more meltwater could be added to the sea.

Sea levels have been rising

one to two millimeters a year.

If more drastic melting occurs,

for instance, if the West Antarctic Ice Sheet

were to melt or move into the ocean,

global sea level would rise

approximately eight meters...

automatically flooding many low-lying areas

and increasing the storm-surge risk.

A sea-level rise of this scale

cannot be practically defended against

with traditional flood defenses.

Preventing the ice from melt occurring in the first place

is our best hope to avoid

a dramatically reshaped landscape.

For instance, much of Florida

could be underwater

in a worst-case scenario.

Flooding due to ice melt

doesn’t just occur because of rising sea levels.

It can happen inland as well.

Mountainous areas can contain large stores of water

in the form of snow caps and glaciers.

In Europe, actually 30% of floods are driven by snowmelt.

The snowmelt floods are actually occurring more often

and occurring earlier in the year.

Glaciers are literal rivers of ice,

containing many thousands of tons of water.

Central Asia’s glaciers contain

the third largest mass of fresh water in the world.

Springtime brings warmer temperatures

and flash thaws.

The meltwater can be sufficient

to cause dramatic flooding at lower altitudes.

As glaciers melt,

lakes can often form in glaciers.

This erodes the land

and creates a depression that fills with meltwater.

It can burst at any moment if they are not drained.

And then the threat for the community will be

that suddenly, hundreds of thousands of cubic meters

will come downstream and will wash anyway everything.

And when I say wash away,

it’s really, wash away their houses,

their livelihoods and of course the people themselves

and their animals.

A glacial lake outburst occurs

when a dam made of ice or terminal moraine,

holding back a glacial lake, fails,

causing flash flooding

and the release of rocks and other debris.

Ice can also cause floods when it melts too slowly.

The Huang He, or Yellow River,

is China’s second longest river.

It is also a river that is prone to frequent flooding.

Parts of the river can freeze

and then thaw at different times.

Ice can form and block parts of the river,

causing a wall of water to develop behind it

which can then eventually spill out

and cause mass flooding.

Rivers such as these can become a never-ending hazard

and have the capability

to unleash huge quantities of water

both in winter and spring.

Ice can cause floods

and, surprisingly, fire can too.

Uncontrollable wildfires are a deadly disaster

perhaps not usually associated with flooding...

particularly as they are opposite in their requirements.

Floods require moisture,

and fires, the absence of water and drought conditions.

Surprisingly, wildfires can increase flood risk.

Rainwater that falls on hills and mountains

can cause floods downhill if the water flows unabated.

The faster water flows downhill,

the more likely a flood is to occur.

The water supply needs to be fast enough

to overwhelm a location’s ability

to remove the excess water.

Vegetation such as forests reduces the flood risk

because trees intercept some of the water

and the root systems slow the water down,

giving it more time to soak into the soil

rather than flow downhill

and contribute to any lowland flooding.

Fires clear the tree cover,

resulting in nothing to slow down

and intercept the water.

It runs down hill uninhibited,

free to contribute to any flooding.

The charred ground is less permeable,

preventing the water from soaking in.

It has nowhere to go but downhill,

potentially picking up fine ash from the fire

and creating dangerous mudslides

as well as dumping water quickly

on the now flooded lowlands.

Burn scars increase the flood risk

in ways that are similar to covering large areas of land

with concrete.

It concentrates the flow in a similar way.

In some cases,

less than half an inch of rain

is enough to trigger flash flooding.

The most damaging floods are flash floods.

So these happen when we have

a very sudden, heavy amount of rainfall

falling over the land.

And when this happens in urban areas,

it can take everybody by surprise.

And so these are very intense events

that people aren’t prepared for.

We find it very difficult to predict these events.

And so these can be actually the most dangerous.

After a wildfire, eventually the land recovers

and the vegetation starts to grow back.

The flood risk diminishes

in proportion to the density of ground cover.

Each burn scar poses a unique risk of flooding

due to a variety of factors that need to be considered:

The proximity to human settlements,

burn severity,

steepness and size of the burned area.

This, however, does take time,

and upland burn scars in many places

are considered a flood risk

for at least two years after the fire.

In December 2017,

the Thomas Fire burned 708 square kilometers

of Southern California.

It was the largest wildfire in California’s history.

November is normally

the rainy season for California,

but that year the rains didn’t come until January,

allowing the fire to burn for over a month.

It took until January the 12th, 2018,

before the fire was brought under control.

The rains helped put the fire out,

but they also triggered flash flooding

made worse by the extensive burn scars

produced by the flames.

Heavy rain that had fallen on burn-scar areas

from the devastating Thomas Fire

triggered waves of flowing mud, rock and debris.

On January the 9th, 2018,

the Southern California town of Montecito

became overwhelmed with destructive mudslides

which came crashing down onto homes and roadways.

Hundreds of homes were damaged or destroyed.

Two thousand and seventeen,

the same year that Hurricane Harvey

dumped trillions of gallons of water on the U.S. coast,

countries in South Asia also suffered

from a catastrophic monsoon season.

Flood can affect just an individual house

or an individual area,

but it can also affect entire communities and entire cities.

In fact, the most damaging floods

can even affect multiple countries at a time.

The main areas affected included India,

Bangladesh and Nepal.

These are lower-income countries

with large populations of people

in the potential flood zone.

When there’s so much water

and a country can’t deal with that by rescuing people,

getting people out the way,

communities are left to fend for themselves.

And that can really make these disasters deadly.

Bangladesh in particular is prone to flooding.

It’s situated on the Brahmaputra River Delta.

Eighty percent of the country

is considered part of a floodplain,

with a large proportion of the country

never rising more than five meters above sea level.

Because it’s so flat,

when Bangladesh floods,

the water has nowhere to run off.

This results in long-lasting floods

that submerge the land for weeks at a time.

Floods in Bangladesh are fed by rainfall,

water flashing off the hills above

and storm surge from its coast.

Every year, it deals with this triple flood threat

causing floods that cover up to 18% of the country

most monsoon seasons.

The monsoons are very tricky

because every year from June to September

these regions rely on this monsoonal rain

for crops and for their agriculture.

But when you have a very intense monsoon season,

this can then lead to devastating floods.

In addition to being low-lying,

Bangladesh is a densely populated country

with 165 million people.

In many areas,

regular small-scale floods

are a blessing to farmers.

They irrigate and provide nutrients for crops.

However, this, in turn,

attracts more people to these flood-prone areas

because of the rich farmland.

Unfortunately, when large-scale floods hit,

there are more people living in the affected areas.

Building flood defenses

represent a considerable engineering challenge.

Water is heavy,

and in quantity, floodwaters impose

considerable pressure on any flood defense.

They need to be built to withstand the pressure.

The building of these defenses are resource-heavy

in terms of materials, labor and cost.

Countries with a smaller gross domestic product

have less money to invest in adequate flood defenses.

This can result in a greater flood impact

than would have potentially occurred

in the better-funded nations.

However, flood preparation takes many forms.

And even with its limited resources,

Bangladesh is used to flooding

and in 2017 was considered by many

to be better prepared for flooding than India.

The economic impacts of floods are huge.

They not only affect individual people and their households

but they affect the whole government,

the whole way of doing business.

We can have business loss occurring

for months after a big flood,

and that doesn’t even take into account

the economic cleanup.

Bangladesh’s experience of regular flooding

resulted in more investment in flood management.

For instance, public schools and mosques

were built with the ability

to also serve as shelters during flooding.

In previous floods, food supplies ran out,

partially due to the disruption to farming

but also because the floods prevented the easy distribution

of emergency food to affected areas.

To prevent this from occurring,

in 2010, Bangladesh instigated a policy

of maintaining a food surplus.

Now grain is stockpiled for use in the event of disaster.

The severe floods in South Asia in August

happened in the three connected countries

of Nepal, India and Bangladesh at the same time.

Their river systems are interconnected

across the vast geographical Ganges-Brahmaputra basin.

These are very, very large rivers indeed,

and they have a lot of power associated with them,

so when you get that amount of rainfall,

with these huge rivers

and you have people living in the way,

perhaps not with very strong homes,

nor the ability to move themselves

and their livelihoods out of the way,

then you will get people dying.

Floods, however,

don’t respect international boundaries.

They are a transnational affair.

Cooperation between countries is needed

to ensure floods on this level can be dealt with

and those affected can be reached.

If you see the extent of the flood,

it can happen for miles and miles.

And people living in very rural areas

can be cut off from the major centers.

And so, literally, you have no communication

and no means to communicate with people back,

and the authorities in the city,

so are just dependent on the aid agencies

and first responders to find them.

In India,

streets in Mumbai turned into rivers

and people waded through waist-high waters.

Rainwater swamped

the King Edward Memorial Hospital

in central Mumbai, and doctors feared

the rainwater would spread infection

as the water mixed with rubbish and detritus.

In Nepal, the floods spanned across

and impacted large parts of the country,

with 35 districts affected

and more than 190,000 houses damaged or destroyed.

The floods displaced tens of thousands of people

and caused clean water and food shortages.

Disease and infection is an ongoing problem

with all flooding,

but particularly in lower-income countries.

Floodwater mixes with sewage and animal waste.

Direct contact with these polluted waters

increases the risk of waterborne diseases

such as wound infections, dermatitis, conjunctivitis

and ear, nose and throat infections.

Floodwater can also contaminate sources of drinking water,

a major risk factor for outbreaks

associated with waterborne diseases

such as typhoid fever, cholera,

leptospirosis and hepatitis A.

Mobile phones have turned into the ideal tool

for alerting populations due to their extensive use.

The most important thing for protecting lives

during a flood event is early warning.

If people are aware of the event ahead of time,

they can take precautions.

SMS messaging used in Bangladesh

is a fast and efficient way of spreading timely warnings

to large sections of the population quickly

and more efficiently than other communication infrastructure.

India, however, struggled to get the message out.

Imagine the misery people went through.

If we had an early-warning system,

a lot of lives could have been saved,

people would have moved to safer places.

The help has to come from government,

and I’m very skeptical that it will come

in the quantities that it is required.

So we are doomed.

Global forecasting centers are able to provide

the science and forecast capabilities

to individual governments and authorities,

but it’s up to the local authorities and governments

to provide the warning to individual people.

Even with evacuation instructions,

populations need somewhere to evacuate to.

Infrastructure is important.

When the floods hit India,

many chose to stay in the affected areas

to protect their homes and belongings.

Evacuation efforts were hampered

by the sheer number of people affected

and displaced by the flooding.

Forty-one million people were affected that year.

It’s very difficult to provide aid to that many people,

particularly in areas where the existing infrastructure

is weak or limited.

With as much as a third

of Bangladesh underwater,

humanitarian efforts were severely challenged

and the 2000 medical teams deployed

were only able to do so much.

One of the biggest problems with floods

is you don’t actually see some of the worst devastation.

We see helicopter pictures of people standing on roofs,

but the people who are dying,

the people who are really injured,

perhaps we don’t see because they’re not reached

by the rescue efforts.

With rising sea levels,

Bangladesh remains at considerable risk

of future flooding.

In recent years, the building of flood defenses

has intensified,

with the World Bank earmarking

two billion U.S. dollars

to fund one of the largest programs

of building and repair of existing dikes and embankments,

thought to protect up to 42 million people.

Embankments are not the most effective flood defense.

They do damage to the ecosystem and can fail.

They are, however, more affordable

than other more engineered solutions.

Bangladesh is a densely populated country

with tens of millions of people living close to sea level.

If sea levels continue to rise

and floods can’t be prevented by physical defenses,

we could see the rise of flood migration.

Large populations of people may be displaced from their homes.

Those that rely on the land for their livelihoods

could experience extensive financial losses.

Sea level rise

and the dramatic floods that follow

could displace millions of people.

This could cause a refugee crisis in affected regions

which could spill over to neighboring countries

as populations move from the flood-ridden areas.

In terms of limiting climate change

and developing better flood defenses,

the stakes are high.

International responses are needed

because floods are a transnational

rather than local issue.

There’s nothing we can do to protect every single person

from every single flood, so we need to have

preparedness actions in place.

Those can be evacuations,

they can be temporary barriers that come in,

they can be other ways of diverting floodwater

into other areas.

The 2017 floods in Texas

received extensive media coverage in the West.

Unfortunately, the dramatic scale

of the flooding in South Asia wasn’t fully represented

in the Western media

compared to smaller Hurricane Harvey.

Because a dramatic flood was already happening in the U.S.,

it seemed they didn’t need to cover another flood.

Natural disasters like floods occur around the world,

impacting both rich and poor countries.

The vast majority of casualties in these events

happen in the developing world.

This happens for several reasons.

Wealthy countries have more money available

to invest in flood defenses,

potentially reducing or even stopping the flood.

Better infrastructure and rescue services

limit the loss of life

and financial insurance is usually in place

to support rebuilding after the waters recede.

Poorer countries lack many of these things.

They also often don’t have

the same degree of urban planning,

with shantytowns built without design

or regulatory planning approval.

Populations in lower-income countries are more vulnerable,

with more people living in the wrong place.

A strong communication infrastructure is often lacking

and it can be more difficult to get the word out

to warn of the need to evacuate.

Also, poorer people may be less able to evacuate.

They may not have the means to travel quickly enough

or have anyplace to go.

The statistics confirm this story.

The floods of 2017 killed 88 people in Texas,

but over 1200 people died from the South Asia floods.

Water is required for life

and flooding is a natural climatic event.

Floods can be relatively benign and easily managed.

Sometimes they are a net positive,

irrigating the land and washing away pollutants.

However, in many parts of the world,

floods can be much more deadly,

particularly for those living in poorer areas.

In many locations, human activities

such as agriculture, climate change,

deforestation and urbanization have added to the flood risk.

So we see every year these huge floods come through,

and it’s very worrying.

So we think that there is some kind of link

with climate change.

And we see, of course, more people in the way

as populations move into more at-risk areas.

They need to think about adapting to these big floods.

We know that it floods already,

but we think it’s going to get worse.

The sheer power and quantity

of water involved in some of these disasters

makes elimination of risk impossible.

The quantities involved

can be beyond human ability to prevent.

In many cases, people live in flood-prone areas

because they have to.

As world population grows,

countries become more crowded,

people have less choice about where they live and work,

resulting in more and more people

living in areas of high flood risk.

If a flood can’t be prevented,

better planning is needed

to ensure populations are more able

to withstand the hardships of flooding

and are in a stronger position to bounce back and recover.

Floods are a deadly disaster that can’t be prevented.

With forethought, planning and investment,

there are better ways to avoid injury

and loss of life associated with these terrible events.