Original subtitles

Landslides are among the most destructive forces in nature.

They occur with devastating speed and deadly consequences.

Nothing can be done to prevent a mudslide once it starts,

as its power tears away everything in its path.

One of the most shocking examples

occurred in a Welsh mining village called Aberfan,

when an entire generation of children were wiped out,

as their school was engulfed by a mudslide.

We also look at the devastating landslides

to hit California early in 2018...

as well as the loss of an estimated 30,000 people,

who were buried or swept out to sea

when a devastating series of landslips

wiped out a 100-kilometer-long coastline of Venezuela.

A mudslide, or debris flow,

to give it its proper, technical name,

is a moving mass of loose mud

mixed with a combination of sand,

soil, rock, water and air

that travels down a slope pulled by the force of gravity.

To be classified as a debris flow,

the moving material must be loose

and more than half of the solids in the flow

must be larger than sand grains.

The debris flow can contain material the size of gravel,

pebbles, cobbles and even boulders,

and may reach terrifying speeds

of up to 160 kilometers per hour.

On the opposite end of the scale,

a debris flow can be so slow

that it will only move down a slope a few meters each year.

A mudflow, on the other hand,

consists of a mass of water

and particles the size of sand or even smaller.

It will cascade rapidly down a stream,

canyon or ravine,

and may prove to be just as deadly and destructive

as a debris flow.

Mudslides occur after water quickly saturates the ground

on a slope.

One of the key things about debris flows,

or mass movements on the slope,

is that they’re usually set off by water.

Not all of them, but the majority of them.

Particularly, the mudslides that we’ve got in this episode

all require water.

So one of the first things you need to do

is make sure your slopes are well drained,

and actually remove that hazard from the slope, if you can.

This is often caused by heavy rainfall

or rapidly melting snow.

Because they need water to form,

mudslides tend to happen during wet seasons.

They can also be triggered by earthquakes.

A landslide that occurred in 2008

as a result of the Wenchuan Earthquake

in China’s Sichuan province killed 20,000 people,

roughly a quarter of all the deaths attributed to the quake.

Other causes of landslides include volcanic eruptions,

a change in the level of groundwater,

repeated freezing followed by thawing,

and erosion that leads to slopes becoming steeper.

Changes to a hillside caused by human activity

such as construction or deforestation

can also contribute to mudslides.

In 2014, a deadly landslide in Washington State,

which killed 44 people,

was blamed by many on deforestation.

Years of chopping down trees

had stripped the hillside of strong roots

and left it vulnerable to the effects of heavy rain.

Construction of roads and housing,

and uncontrolled changes to land,

such as not draining an area properly

before building on or near it,

can create the conditions ripe for a mudslide.

Wildfires, which destroy the roots of plants,

may also lead to mudslides.

This is because the roots help bind the soil together,

making it stable and less likely to be swept away.

Overgrazing by farm livestock can have the same effect.

Another contributing factor

may be the dumping of debris and other landfill

into channels where mudflows can occur.

Water breaching a dam, levee, irrigation ditch

can also cause mud and debris flows

as the escaping water quickly mixes

with large amounts of loose soil.

Often the sheer weight of matter such as snow,

stockpiles of ore and other waste materials

can put pressure on unstable hillsides

and unleash a terrifying mudslide.

As it moves downhill,

a mudflow can sweep up nearly anything in its path,

including debris left by previous flows.

As it gathers more material,

the flow will increase its erosive power

and destructive energy.

In the United States,

landslides result in an average of 25 to 50 deaths per year.

Throughout the world,

the highest number of people killed by landslides

occur in various parts of Asia,

Central and South America,

and in the Caribbean.

Just between 2004 and 2010,

scientists have calculated

that landslides killed over 32,000 people--

Or more than 4500 individuals per calendar year.

There are many strategies that can be put in place

to decrease the risk of mudslides.

A lot of things are already being done.

We can already start to work out where they’re likely to occur.

We can model the way in which they move,

using computer simulation techniques.

We can identify the conditions that trigger mudslides.

We can ensure that there’s planning regulations in place

to ensure people avoid the areas

where mudslides are going to occur.

And we can put up some form of mitigation measures.

We can build check dams

to stop mudslides affecting an area.

We can make sure there are evacuation plans.

You have warning systems in place

so that people can be evacuated. So a lot is being done.

We can look at the geological conditions that exist,

where the ground has shown itself

to be susceptible to mudslides.

So we can identify a lot

about where the mudslides are going to occur.

What we say with things like mudslides

is that they’ve got many different causes,

but, in fact, there’s only one trigger.

There’s some single event that usually triggers the movement.

What we got to do is see what the other conditions are,

identify them, and then anticipate the trigger.

And most of the time, the trigger will be

a period of sustained and heavy rainfall.

There are a variety of features

that engineers can put in place to armor a slope

and prevent it from giving way.

Majority of cases I’ve seen, usually, for example,

along the sides of motorways, you might see either gabions,

which are like, sort of, like metal baskets

with rock material inside.

And again, they’d have drainage through them

to allow water to get out.

Because if you get the water in there,

it’s still going to go.

Another approach might be to use large,

really large boulders, very large boulders,

5 meters across, something like that,

basically, to protect the slope.

During rainfall,

experts recommend extreme caution

on or around steep slopes,

and looking out for visible signs

that a landslide may occur.

The sorts of indicators that a slope might fail

can be very varied. If you’re on the slope itself,

away from the buildings,

generally, what you’d be looking for

is terrain or a slope that looks a bit different.

Usually, it might look a bit hummocky, for example.

There might be cracks in it. You can look at the trees.

The trees may not be growing vertically.

They may have some asymmetry to them,

because trees like to grow upwards.

But if they’re being forced down the slope,

then they might have some asymmetry to their growth.

So you might see things like that.

But primarily, the first thing you would look for

is that different texture to the slope.

If there are buildings or roads in the way,

you might see cracks in the road.

You might see bulges in things like patios,

or tarmac in a road,

things like that, which indicate the slope is starting to move.

So you can use features that are both natural

and obviously affecting man-made structures as well.

The consistency of a mudflow

is rather like pancake batter.

They tend to pick up speed

and grow in size as they gather debris.

Mudflows are similar to flash floods

in that they can occur very suddenly

and are extremely dangerous,

because people may have little or no warning

of the impending disaster.

Mudflows can scour across land,

leaving deep gouges and debris,

which can severely impact agricultural land

and destroy crops.

They can also have a severe impact on vital infrastructure.

They can rip up and block roads,

damaging utility pipes which carry water,

gas and sewage.

Electric pylons and communication lines

are particularly susceptible,

as they are often constructed with weak foundations.

Such damage to infrastructure

is liable to hamper relief efforts.

If a landslide reaches a river,

the mud and rock will flow into it

and can eventually reach the ocean.

This can cause large silt deposits on the riverbed,

which is harmful to marine life,

as well as local human populations

and animals relying on the water.

The potential upside

is that the nutrients brought down by the slide

will improve the quality of plant growth in the water

and so, eventually, enhance the life which depends on it.

The deadliest types of mudslides are called lahars,

which are associated with volcanic activity.

They are often caused by a sudden

and catastrophic melting of ice and snow

from the heat of the volcano.

The lahar,

which has the consistency of freshly mixed concrete,

has a terrifying power

that can destroy anything that stands in its path.

Lahars can also occur when heavy rain

makes volcanic deposits of ash

suddenly break loose from a mountainside.

The deadliest mudslide in recorded history

was a lahar that occurred in 1985 in Colombia,

following the eruption of a volcano

known as Nevado del Ruiz.

The eruption resulted in a devastating series of lahars

that swept down the mountain towards the city of Armero.

Residents were buried under nearly 5 meters of debris.

Of the 28,000 people living in Armero at the time,

barely 5000 survived.

It wasn’t simply the worst natural disaster

in Colombian history,

but one of the worst natural disasters

ever to occur on Earth.

As with any natural disaster,

the cleanup after a landslide

can be an enormous undertaking.

Fortunately, developed nations have strong systems in place

to help affected areas get back to normal.

But even they are sometimes challenged

by the sheer scope of the relief effort necessary.

In the United States, mudslides cause

an estimated $1 billion worth of damage per year.

For developing nations,

there is often less money and fewer plans in place.

They also suffer disproportionately

when it comes to casualties.

This difference is due to a number of things,

including the efficiency of basic infrastructure

and emergency services,

and the access of health care

to treat people who are injured or left homeless.

Tackling poverty and improving construction standards

in high-risk areas may go a long way

towards stemming the flow of losses from landslides,

as well as other deadly natural disasters.

They become a serious threat to humans

who chose to live in active mudflow areas.

Although as climate patterns change,

previously safe areas

may well be considered dangerous in the future.

California, on the west coast of America,

is particularly prone to landslides.

More than 100 residents have been killed by landslides

during the last 25 years.

The majority of deaths occurred

when people were buried by debris flows

while they slept on the ground floor of houses

situated near dangerous slopes.

California is affected by earthquakes,

wildfires and heavy rainfall,

all of which are major contributing factors

to mudslides.

But they are difficult to predict,

because there is often a delay between rainfall

and the triggering of a landslide.

In Los Angeles in 1998,

serious landslides occurred

five days after the rain had stopped.

In some cases, it has taken weeks

before the effects of heavy rainfall

caused the land to give way.

A shocking example of the power of mudslides

occurred in 2018 in the small town of Montecito,

home to some 9000 people.

Leading up to the mudslide,

the community had already experienced severe weather.

The 2017 wildfire season had been the most destructive

in California’s history,

burning over 5300 square kilometers

and killing 46 people.

But what lay behind those terrible wildfires?

Up until 2016,

there had been a five-year drought,

amongst the worst in history,

which had parched the landscape.

The drought ended with record rainfall,

producing lush vegetation,

which then turned to kindling,

following the hottest summer on record.

At the beginning of December,

the coast of California was swept by the Santa Ana winds,

comprising of warm and extremely dry air

from the deserts inland.

They fanned wildfires across the southern part of the state,

which were made worse by the lack of rainfall

during what is normally the region’s wet season.

In late December, the Thomas Fire,

one of the largest wildfires ever to hit California,

ravaged over 1000 square kilometers

of the Santa Ynez Mountains.

It scorched whole areas

of Santa Barbara and Ventura counties,

burning large amounts of vegetation.

This destroyed the roots

that supported the surface soil on hillsides,

leaving them much more vulnerable to landslides.

On the 5th of January 2018,

a strong low-pressure system

and cold front developed off the coast of California.

The danger to those communities

living in the shadow of the parched

and burnt-out mountains was immediately obvious.

Residents of Montecito

were issued with compulsory evacuation orders.

The authorities were aware of the extreme danger,

largely due to research that had been done

by the U.S. Geological Survey.

They had studied data from past extreme weather events

going back decades, and created models

that could predict precisely how much rain would be needed

to trigger a mudslide in any given area.

As the storm approached the Californian coast,

authorities were able to issue the first warnings

days before the mudslides occurred.

By Monday, the 8th of January,

the weather system reached the mainland

and unleashed a vicious winter storm.

After almost a year of drought,

Southern California was deluged by extremely heavy rain.

There were mandatory evacuations

in parts of Los Angeles,

Santa Barbara and Ventura Counties,

due to a risk of mudslides

in areas which had previously been affected by wildfires.

Over 21,000 people were supposed to leave their homes.

Many ignored the warnings.

Only around 10 to 15 percent

of Santa Barbara County residents evacuated.

What intrigues me always about these sorts of events

in developed countries is that often the loss of life,

although tragic, is usually a lot lower than it is

if you go into developing countries.

I think it was something like 21 people killed in this event.

But the actual infrastructure damage was just huge.

This is one of the events that I believe

was being anticipated,

and evacuation plans were in place.

And again, that’s something you do see

in many developed countries.

that they actually have evacuation plans in place,

and they appear to have been very effective.

However, there’s always a problem with evacuation plans

because if you evacuate people too often,

they sort of suffer from fatigue of evacuation

and tend to ignore some of the signs.

And that’s of concern.

And I believe that happened in Santa Barbara.

I decided not to evacuate when I got the warning on my phone,

because it was in the middle of the night--

Well, 2 or 3 in the morning.

And my concern was if I evacuate,

I might get trapped in my car with flowing mud.

Many people had just stopped believing

that disaster would strike them.

They were tragically wrong.

At 3:30 a.m. on the 9th of January 2018,

a thunderous river of slurry

descended off the hills into the heart of Montecito.

By the time the mudslide hit the first few homes,

it was so powerful that it was carrying

rocks and boulders the size of cars

from the Santa Ynez Mountains down creeks and valleys.

Survivors reported that the flow

sounded like a freight train and came in an instant,

as if a dam had broken

and completely engulfed their houses.

The debris flows were up to 5 meters in height,

moving at speeds of 30 kilometers per hour.

The devastation was spread over an area

of nearly 78 square kilometers.

Over 20,000 people lost power,

100 homes were completely destroyed,

and 300 damaged.

Firefighters who first arrived

said the area looked like a First World War battlefield.

They had to pick their way through debris,

piles of fallen trees, and around displaced boulders,

in a desperate attempt to find survivors.

For most people that are here on this incident,

we’ve never seen an event like this.

This is very unusual to have something to this magnitude.

Search crews made up of rescue workers and citizen volunteers

were also sent out to locate the missing.

They used long poles to probe the mud and slurry

trying to locate bodies.

Power lines were down.

The large aluminum poles that held them in place

had been snapped in half.

Water was pouring out of shattered pipes.

A mandatory evacuation was ordered,

and thousands of people fled the area.

First responders performed more than 50 rescues.

Crews in helicopters hoisted survivors from mud and debris.

Rescue workers used all-terrain vehicles,

but the search for survivors was hampered

by roads blocked by rocks,

fallen trees and downed power lines.

A 50-kilometer section of the coastal Highway 101

from Santa Barbara to Ventura

was completely shut down,

as sections were filled with 60 centimeters

of mud and debris.

Access to Santa Barbara from the Los Angeles area

involved a 420-kilometer detour

around the Los Padres National Forest.

Some relied on private ferries

between Ventura and Santa Barbara

to bypass the closure.

By the 11th of January,

two days after the disaster,

anxious relatives were still waiting for news

of missing loved ones.

Governor Jerry Brown estimated

that the search could take weeks,

though he still had hope that people would be found alive.

By Friday, over three days

after the mudslide struck Montecito,

the confirmed death toll had reached 18.

We just feel very sorry

for the people who lost their homes and their lives.

How do you describe it?

It’s devastating, what happened.

Uh, so much destruction.

Over 1200 emergency workers were in a race against time

to find the five people still unaccounted for.

Meanwhile, heavy equipment was brought in

to help the cleanup effort.

Crews from Caltrans,

the California Department of Transportation,

cleared nearly 4 meters of mud from the highway.

And on the 21st of January, five days into the crisis,

Highway 101 was fully reopened.

A total of 21 people were killed by the mudslides,

another 28 were injured, four of them critically.

But casualties in Montecito

would most likely have been even greater

had it not been for warnings

from scientists and government agencies

in the days and hours leading up to the tragedy.

In the mountains of Southern California,

there is a terrifying cycle of wildfires and debris flows.

There is even a possibility

that this cycle is getting more intense,

due to changes in the climate

and increased human development.

The average wildfire season lasts

two and half months longer than it did in the 1970s,

and the area of land burned since 1984

is twice what scientists at the time predicted.

If you extend the actual length of the period for the fires...

is that if you enter into the season

where you’ve then got snow on the higher ground,

the dust, or the soot, from the actual fires,

can actually, if it lands on the snow,

can actually encourage the snow to melt more quickly,

because it’s changed its reflectivity,

so it’s albedo.

And so you melt the snow, you get more water.

Therefore, more erosions.

Science is starting to understand

how the cycle works,

and provide some idea

of when it will be at its worst.

This information will be vital

if people continue to build more and more houses

at the feet of mountains

that regularly unleash their debris flows.

If wildfires are becoming more common,

it is more likely that the mountainsides will give way.

And it is not only the roots

that hold the underlying soil together that is burned away.

Even the creatures that live in the soil

and would normally aerate it,

helping it to better absorb rainwater,

are killed by the fire,

as well as the ground cover

that provided protection against the downpours.

The plants that thrive

in Southern California’s chaparral,

the shrubby heathland that typifies the area,

play a particular role in the problem as well.

Those shrubs and lie-lowing waxy plants

have a resin-like coat on their leaves

that helps them to retain moisture,

enabling them to survive drought.

The relationship between wildfires and debris flows,

or mudslides, is quite interesting,

because what tends to happen if you’ve got a wildfire

is the superheating of the ground can release,

from the vegetation, it burns the vegetation,

and it can release the waxy substances from the plants.

They come out mainly as a kind of vapor, and it can solidify,

usually below the soil surface, around the soil particles.

And it forms this, what they call "hydrophobic soil."

It sheds water, and it won’t let water pass through

the actual soil profile.

So that means you’re more likely to get soil runoff,

and then that can take with it mud and debris

and sediment from the surface,

and can lead to all sorts of erosion problems.

Elevation and the relief, in other words,

of the highest to the lowest point in a catchment

is actually quite important.

If you’ve got steeper slopes, you’ll get more runoff.

And therefore, you’ve got less stable slopes, generally.

With regard to generating debris flows,

you’re more likely to generate them on steeper slopes.

The mudslides in Montecito

are a tragic reminder

that natural disasters threaten many U.S. homes,

even within prosperous neighborhoods.

Aberfan, a tiny mining village in Wales,

could not be more different

to the affluent coastal community of Montecito.

At 9:15 a.m. on the morning of 21st of October 1966,

this small village was plunged into despair

when thousands of tons of waste from a coal tip

roared down a hillside,

engulfing a school and several homes.

The village of Aberfan

is a community that grew up

around the Merthyr Vale colliery.

Merthyr Vale started operating in 1869,

and was once one of the largest of the 600 coal mines

that were so crucial to the development of Britain.

Coal was so vital to the economy of the time

that it was known as black gold.

It powered the Industrial Revolution,

which enabled Victorian Britain

to become the world’s superpower of the time.

But by 1966,

the importance of coal was in decline,

replaced by oil,

and several pits had already closed.

In Aberfan,

the number of miners had fallen from over 2000 to about 800.

But it was still considered vital to the local economy.

Since the coal industry had been nationalized

after the Second World War,

the National Coal Board, known as the NCB,

had taken control of U.K. mining

and wielded enormous power.

It was seen as the protector of a dwindling coal industry

and was treated with a respect bordering on reverence.

For around 50 years,

waste material from the nearby colliery, known as "spoil,"

had been tipped in a series of slag heaps

onto the tops of the surrounding hills

above the village.

In the center of the village,

directly below one of the huge heaps of spoil

known simply as Tip Number 7,

lay Pantglas Junior School.

Tip Number 7 had been growing for nine years,

and by 1966 contained nearly 300,000 square meters of waste,

towering 34 meters high.

The children in the back classrooms

would have been able to see the enormous tips

through their window.

There was a regulation in place with the NCB

that any mine material dumped

should not be dumped on top of a spring,

a natural water spring.

And that was ignored at Aberfan.

Numerous complaints had been made

about the dangers of the tip,

including a petition from Pantglas school,

which lay in its shadow, but the NCB dismissed them all.

They made it clear that the cost of moving the tip

would make the mine unprofitable.

In the days leading up to the disaster,

there had been heavy rain.

At 7:30 a.m., on the day of the disaster,

a crew arrived at Tip Number 7 to begin work.

They quickly noticed something unusual.

The tip had clearly moved,

and the track that their crane stood on

had been bent about 3 meters.

Since they had no telephone,

a worker was dispatched to go down on foot

to report the problem.

But no alarm was raised.

Nearby, excited children set off

on their last morning of school

before the half-term holidays.

As they made their way along the narrow lanes

that separated the miners’ terraced houses,

they could have no idea of the horrors that lay ahead.

By 9 a.m., the tip had subsided by another 3 meters.

Minutes later, a vast wall of mud and rocks

smashed into the side of the school

at over 34 kilometers per hour.

We just looked up at the windows,

the front windows, facing the tip,

and you could see like a black--

Like a black mass, like locusts.

Just a mass coming into the classroom.

The slide continued its path of destruction,

engulfing a whole row of houses in the village

before finally coming to rest.

There was this rumbling sound

which got louder and louder as time went by.

And the next thing I remember was waking up.

When I woke, I found myself in this, um...

covered in this material...

with a dead girl on my shoulder.

And I couldn’t move.

There were screams and shouts,

and obviously they got less and less as time went by.

Hundreds of villagers who rushed from their houses

were faced with a scene of utter devastation.

A large part of the school was buried

with their children inside.

Only the shattered roof was visible

above a black sea of slurry.

As news of the disaster spread,

the emergency whistle sounded in the colliery.

Miners emerged and ran to the school.

Many of their wives were already there,

clawing at the slurry,

some with no skin left on their hands,

desperate to reach their children

who were crying for help,

children that only a few minutes before

they had waved off to school.

Doctors and nurses set up a triage in the playground

at the school’s entrance.

Men and women of the community

carried the injured children to the triage,

where they were assessed by the waiting medics

and provided with first aid.

The area was declared a disaster zone,

and the seriously injured were taken to hospital.

Roads for miles around became gridlocked

as emergency services, the Army and Civil Defense,

tried to get to the scene.

They were joined by miners from surrounding pits,

as well as thousands of volunteers.

First local, then national

and eventually international media,

descended upon the village.

Aberfan was the first British tragedy

to be covered extensively on television,

as the scale of the catastrophe unfolded

in pictures which were beamed around the globe.

The plight of Aberfan horrified

and deeply moved the watching world.

In all, just 35 people were rescued

out of the mass of coal slurry and debris.

The last rescue occurred at 11 a.m.

After that, it was only bodies that were found.

Specialist officers arrived

to set up a temporary mortuary.

They needed to take the bodies somewhere nearby,

and decided on Bethania Chapel,

which was just down the road from the school.

The grief of their relatives is almost unimaginable.

As darkness fell,

arc lights were set up so they could continue to dig

all through the night.

The following day,

both Lord Snowden, husband of the Queen’s sister,

and later the Duke of Edinburgh,

walked among the 2000 emergency service personnel

and volunteers who were working in the disaster area.

Many of them had been laboring continuously for over 24 hours.

It was nearly a week before all the bodies were recovered.

Nearly half of the pupils

at Pantglas Junior School lost their lives.

They were between the ages of 7 and 10.

Five of their teachers also died.

Most of the victims were buried in the village cemetery

at a joint funeral that was attended

by more than 2000 people.

Today, the site of what once was Pantglas Junior School

is a memorial garden on the outskirts of the village.

A peaceful place with wide, paved borders,

trees and bushes.

It’s almost impossible to believe

that we have to have a tragedy

before we deal with the consequences.

That’s exactly what happened at Aberfan.

Aberfan resulted in all these tips,

you know, if you know the area,

there were an enormous number of tips

which were perched above villages in the area.

And, you know, they could easily have failed as well.

And evidence was ignored, it just wasn’t accepted,

even at the NCB.

Because no miners were killed underground,

in theory, they didn’t even need to report the fact

that this tip had failed,

because that wasn’t deemed to be part of their responsibility.

You know, it’s an appalling situation,

and a savage indictment on the regulations

that were in place at the time.

Aberfan was a tragic event caused by a single landslide.

It would seem unimaginable that such a phenomenon

could occur more than once in a century.

But over the course of a nine-day period

in December 1999,

torrential rains fell on a mountainous region

of Venezuela,

causing another flow of deadly mudslides

that devastated the state of Vargas.

The landscape of Vargas is extremely steep and rugged.

The distance between the coast

and the 2700-meter peaks of the Sierra de Avila mountains

is only 6 to 10 kilometers.

The rivers and streams of this mountainous region

emerge from steep canyons onto flat alluvial fans,

before emptying into the Caribbean Sea.

These alluvial fans are triangular in shape,

and are formed by deposits of sand,

gravel and silt, brought down by water

flowing off the slopes of the mountains.

In Vargas, little relatively flat land

was available for development,

with the exception of the alluvial fans.

This coastal city was popular

because of its proximity to the capital,

which is only 30 kilometers away

and is easily accessible

via a pass through the mountains.

Many residential communities had developed

as well as a thriving tourist economy.

Venezuela’s main airport, the Simón Bolivar,

and the major seaport of La Guaira,

which handles around a third of all of Venezuela’s trade,

are also situated in the state.

Because of this,

many people were drawn to work in the area.

But with the flat alluvial fans

already heavily built on for resort towns,

newcomers had no option

but to settle on the steep hills and canyons.

This had a great impact on the life of the poor.

They were known to be dangerous, but for many,

they were the only homes available.

Many of these coastal towns

were developed in a bizarre way,

with luxury hotels, harbors for yachts,

and high-end apartment buildings

in view of the shanty dwellings

clustered on the hills above them.

Although scientists had known of the dangers from landslides

in the area, no hazard maps were ever produced,

or warning systems put in place.

This, despite the fact that during every rainy season,

which normally runs from March to October,

about 200 homes were estimated to have been swept away

by rain and mud.

The best way to avoid any form of landslide,

of which mudslides are a type, is basically,

to not build in their path,

to identify where the areas that are susceptible

to any kind of movement, and just avoid them.

And that’s proper planning regulations.

You have the right regulations in place,

properly instigated by the authorities,

and therefore, you can avoid a lot of the problems.

There are so many shantytowns built up

around major areas of population with no regulation whatsoever,

and often these are in very vulnerable places.

The weather in 1999 was by no means normal,

with torrential rain continuing into November and December.

The reason for this unusual out-of-season rainfall

was a cold front that settled over the coastline,

interacting with the moist air

flowing south from the Pacific Ocean.

Rain fell continuously for 16 days,

and the ground was completely saturated.

On the 2nd and 3rd of December alone,

rainfall amounting to 20 centimeters

fell in the region.

But even worse would follow,

when a major storm inundated the area

with over 90 centimeters of rain

between the 14th and 16th of December.

Many thousands realized the danger they faced,

and fled the region to higher ground.

Many people were unable to get away in time,

and were still in their homes when the landslides hit.

Unable to absorb anything more,

the soil finally gave way.

Numerous floods and debris flows occurred

in the later hours of the night

of the 15th of December,

persisting right through to the afternoon

of the following day.

Avalanches of wet mud and debris

began hurtling down the hillsides

in a maelstrom that tore away everything in its path.

The flow, which was up to 9 meters deep,

hurtled down the slopes

at speeds of 60 kilometers per hour,

carrying huge rocks,

some as big as 9 meters in diameter.

With little or no warning,

thousands of people were swept away,

as their homes collapsed in the seething mudslide.

Houses lower down the slopes were destroyed

when the buildings above collapsed onto them.

In some cases, entire neighborhoods

were obliterated in a moment.

Shantytowns and whole villages were buried beneath the mud

or swept out to sea.

Entire towns like Carmen de Uria and Cerro Grande

were completely obliterated.

In Carmen de Uria, an estimated 10 percent

of the town’s 5000 inhabitants died.

Of the 3000 houses that once stood there,

only around 100 were spared

the destruction wreaked by the mudslide.

The once bustling streets and open markets

were reduced to a muddy gorge,

strewn with boulders and rubble from buildings

torn apart in the deluge.

The avalanche of water, mud, trees,

and the wreckage of houses

came to a stop at the bottom of hills and mountains,

where it engulfed high-rise apartment buildings.

Many people were stuck on rooftops for days,

completely cut off by mud and debris.

More than 8000 individual residences

and 700 apartment buildings were damaged or destroyed.

Every aspect of the state’s infrastructure...

vanished within minutes.

All utilities, telephone, electricity, water,

and sewage systems were severely disrupted.

The whole state was virtually cut off from the outside world.

People were unable to find out

what had happened to their loved ones.

Local television stations

allowed relatives to appear on-air

with photos and messages

in an attempt to help them get the information

they so desperately needed.

For weeks, there was no access to relief supplies,

and hundreds of thousands were evacuated from the area.

One thousand survivors took shelter on a golf course

near the resort of Caraballeda,

where they waited to be evacuated.

They were attended to by 18 doctors

who worked for days without respite.

By an unfortunate coincidence,

the disaster coincided with a major government referendum

that was being held at the same time.

Hugo Chávez, who had been sworn in as president

just 10 months earlier,

was seeking a mandate to ratify a new constitution.

Many accused the government

of not executing disaster relief quickly enough,

because military and police resources

were too heavily focused on tasks related to the voting.

On the 15th of December, as the crisis deepened,

there were widespread reports

that looting had become rampant.

President Hugo Chávez called in the military,

with a remit to aid in evacuation efforts

and to restore order.

By the 20th of December, the authorities realized

the seriousness of the situation in Vargas

and declared a state of emergency.

Three hundred and fifty thousand people,

mostly the very poor,

were left homeless by the terrible storm.

Although all members of society were affected,

it was the poor in shantytowns who suffered most,

as their flimsy dwellings were swept away

in the raging mud and water.

The American and Venezuelan Red Cross

joined the relief effort, setting up bases

so that victims could have access

to food and medical care.

Many nations sent assistance

in the aftermath of the disaster.

They joined 13,000 Venezuelan soldiers

who led the relief efforts.

The international community realized that Venezuela

was in the midst of one of its worst-ever natural disasters.

There was clear evidence of lots and lots of mudslides

coming down through the village.

The area was cut off for a considerable amount of time.

One of the issues I remember most about that

was that they had to evacuate

something like 80,000 people from the area,

and they had to declare martial law just to protect the area.

The mudflows in this area flowed out into the sea,

so you couldn’t actually work out how far they ran out.

But again, it seems to be the result of very heavy rainfall,

and a lack of planning in where the developments took place.

The World Bank quickly stepped in to help

with an offer to loan the stricken nation

$150 million U.S. dollars.

Hundreds of thousands of people

remained homeless for many weeks after the mudslides.

The official estimate for the death toll is 30,000,

although it could be as high as 50,000.

At the time, this represented well over 10 percent

of the estimated population of Vargas.

A true figure of the human cost will never be known,

because so many people were buried or carried out to sea

by the debris flows and flooding.

Only about 1000 bodies were ever recovered.

And the fact that it was never known how many people

were living in the shantytowns before the mudslides

further complicated the task of getting accurate information

about the number of deaths.

Estimates of the cost to rebuild

the ruined infrastructure,

and deal with the 150,000 people

who had lost their homes,

was put at between 4 and 15 billion U.S. dollars.

The sheer volume of debris,

rocks and large boulders hauled

make the 1999 event

amongst the largest rainfall-induced debris flows

ever documented.

The disaster highlighted the need

for the country to rethink its land development

and environmental policies.

Plans were drawn up to create new dams

and dig long canals to prevent a repeat of the disaster.

But 10 years later,

many of the once-thriving coastal communities

were like ghost towns.

Apartment blocks and holiday villas remained derelict,

with boulders and dried mud

lying where they settled during the fateful disaster.

And, tragically, there were people for whom

those wrecked buildings were home.

If you can’t plan to stop development,

then you have to fall back on remedial treatments.

And we do have those in place. They are available.

Add to that, you do need to have some monitoring systems.

You need to ensure that you have evacuation plans.

And at the end of the day, yes,

you do need to have emergency plans in place

to deal with the aftermath.

And again, the developed world is so much better,

because it has the resources to have such things in place.

The developing world is where those plans--

Maybe they’re there in theory,

but rarely there are the resources there

to just have plans ready and get things moving quickly.

There can be few more terrifying experiences

than seeing a solid hillside turn into a fluid mass,

capable of smashing through everything in its way,

bringing death and disaster

on a murderous path to the valley floor.

The landslide is truly

one of Mother Nature’s most horrific killers.