♪♪
-Summer 2016, Canning Town, East London.
-I was sitting here, just working away,
and it was raining, so I went outside
and opened the door, had a look.
I thought, "My God, this is tropical."
It was a lot of rain. [ Rain pouring ]
You know, you just don't see
that kind of rain here in London,
and the water just started coming in.
It was crazy.
In over two hours, there was almost a meter of water in here,
sewage everywhere.
Drum kits were floating about in the water.
Amps was just under the water.
Things that survived were things that are on tables.
The roads were impassable because the roads flooded.
The trains couldn't run because it was basically a stream.
The amount of water that was falling filled all the sewers,
and the water is going to find its lowest point
below ground level here.
At the end of the day, how can you cope?
-The world's great cities face threats
they have never before encountered.
New York,
Tokyo,
London,
Miami --
the threats come from the sea,
from above and from below.
These are the problems and their solutions...
♪♪
...for when the water comes.
[ Waves crashing ]
-So, underneath here is
the pump chamber with the pumps.
I know for a fact it's going to happen again.
It will happen again.
It's just a matter of when.
Rebuilding it took a good 10 months.
God forbid it should happen like that again
and for some reason the pumps don't work.
If it happened again, I would just pack up.
-Flash flooding has become commonplace in London.
In 2007, one incident left 1,400 properties in the city flooded.
-There's so much regeneration going on in London
at the moment where any kind of open space has been built on,
so where does all that rainwater go?
It's not being soaked into the ground anymore.
-London faces three challenges.
Summertime rainfall in the UK
has increased 20% in the past decade.
The city is densely developed
along the Thames River floodplain,
meaning all that rain has no place to go,
and the legendary Thames is handling more water than ever
as sea levels rise all around the island nation.
The Thames has always been at the heart
of London's prosperity,
linking the city to the outside world,
but it has also posed a threat.
-London probably has one of the longest flood histories
of anywhere in the world.
There's records of events going back thousands of years.
I mean, there's hundreds of major storms that have occurred
that have killed several thousands of people.
-London has a population of eight million people,
and the initial city was designed
for four million people,
so it's actually doubled over the course of,
we could say, 125 years.
If London stops functioning and London is flooded,
this country, as far as you know it, will stop functioning.
-While the Thames is widely thought of as London's river,
it's actually part of a 215-mile-long series
of tributaries and wetlands throughout southeastern England.
The Thames flows east from Greater London
into the North Sea 50 miles away.
Robert Muir-Wood is a resiliency scientist in the private sector.
-So what we're looking at here is a map
of the Greater London area,
and at the western end here, we have the river,
which comes in from the countryside
to the west of London, comes in,
and the river is getting wider now.
You can see it's also getting a bit muddier
because the tides are very strong.
They're carrying a lot of mud with them,
swings around here and passes into the Westminster area
so the center of government quite close to Hyde Park.
Up here, we get to the city of London, the old center,
which is actually on a slight hill,
so it's actually protected from flood risk.
In the aftermath of every flood or near-miss flood,
the walls in Central London,
which protect Central London from the river,
have been raised.
-As oceans rise, the Thames is affected
because its estuary flows into the North Sea,
and that poses further challenges for London.
-The North Sea has been described
as the perfect storm-surge basin.
It's very shallow.
The shallower it is, the more effect the wind
can have on raising up sea levels,
but the North Sea also funnels as well.
-When wind and storms make the waters of the North Sea rise,
they funnel west into the Thames Estuary
and up the river to London.
-And that wall of water has only one place to go,
and we know what's at the end of this big corridor --
London.
-These storm surges have flooded London
throughout history.
-1928 in the middle of the night,
there was high flow on the Thames
coming into London on the river, and also,
there was a storm surge came in from the North Sea.
In fact, the term "storm surge" was coined
in the aftermath of what happened
because people didn't have a word at the time
to describe what kind of flood this was,
but it actually flooded the areas of Central London,
of Westminster, in particular, drowned, I think, 14 people,
caused several thousand to lose their homes.
-The storm that was London's wake-up call hit the city
with a massive blow in January 1953.
-People went to bed that night
with no idea they were going to flood.
Some people unfortunately didn't wake up the next day.
-The storm began with high winds over the North Sea
battering its shores from Scotland to the Netherlands.
Combining with the rising spring tide,
a mammoth surge powered up the Thames.
-The country was different in those times.
There wasn't any warning system.
There weren't really any defenses, per se.
-At the mouth of the Thames,
the people of Canvey Island had no idea what was coming.
Only 11 years old at the time,
Ray Howard remembers being woken in the middle of the night.
-We were upstairs tucked in bed when,
all of a sudden, my sister came into the bedroom and said,
"Quick, there's water gushing down the street."
-Hundreds of millions of gallons of water
swept through the town.
-People were clinging to their roofs
and just hanging on because of the force of the breach
and the force of the tide and the heights of the tide.
-The storm tide reached London around midnight.
As water rose higher in the Thames,
the BBC issued a warning,
and cars equipped with loudspeakers
were dispatched to rouse the sleeping city.
The east end of the city was flooded
from the Royal Docks into Canning Town.
At London Bridge,
the water reached its highest level ever recorded,
threatening to breach the embankment
and inundate Central London.
-In fact, in center of London, the river was actually brimful.
It was a major event.
-Then the wind turned unexpectedly,
and the surge receded.
The center of London was spared,
but still, the destruction was immense.
-Helicopters, too, have played their part,
flying in supplies for the survivors
and helping to maintain the central services in areas
not yet evacuated.
-Poor people just had no chance.
59 people lost their lives on Canvey Island
in that terrible, terrible evening
but 309 people along the whole east coast of the UK.
-160,000 acres of land
were inundated across the UK.
The damage was the equivalent of nearly $2 billion today,
but it could've been even worse for London,
and the city decided to act.
-That was the foundation as to why London should be protected.
The flood was quite severe, and they realized
that if we carry on in this fashion in the future,
we won't be able to protect ourselves
from this ongoing problem of a tidal surge
leading to the riverbanks,
overtopping and actually flooding the floodplain
all the way down to Central London.
-The options considered were, "Do we do nothing?
Do we move London because the risk is too great?"
Or the third, "Do you build a barrier?"
-London set about bolstering its flood defenses
with nearly 200 miles of embankments,
gates and barriers along the Thames and its tributaries...
...but it would take $2 billion and nearly 30 years
to create the crown jewel of their new system,
the Thames Barrier.
A 600-yard-long floodgate
that runs from New Charlton to Silvertown
across the Thames was finished in 1982.
-Tower Bridge, the last major bridge,
and then the river, still getting wider,
swings around again past the old docks going south
and then north again in a big meander.
This is where Canary Wharf,
big new high-rise financial center, is.
Further towards the east,
the river is getting still wider.
We're heading more out to sea, and then, finally,
we come to the line of the Thames Barrier itself,
so everywhere to the west of that is actually protected
by the Thames Barrier
from the storm surges coming in from the sea.
-Normally, the barrier remains open so boat traffic
can reach the Port of London,
but when a storm surge approaches from the North Sea,
10 curved steel gates rotate up from the riverbed.
This forms a solid wall against millions of tons of water
that would inundate London.
♪♪
Since its installation, it's been used 182 times,
and London has not been flooded once.
Andy Batchelor has been the manager of this marvel
of flood engineering for nearly 20 years.
-The barrier is referred to as the sleeping giant
because if we do our job well,
no one needs to know because London is protected,
so the tides can come and go, the barrier close,
and they don't get their feet wet.
That is the art of good flood risk management.
-For three decades, the barrier has kept the city safe
from storm surges.
-The Thames Barrier has been designed
for a 1-in-a-1,000-year event.
What that means is that there's a 0.1% chance of London
being flooded as a result of that barrier.
That is why it works.
-But while it's been doing its job of keeping London dry,
the climate has been changing,
so now the Thames Barrier faces a new challenge.
-The barrier was designed in the '60s.
Climate change, global warming weren't phrases
in the dictionary then.
-The designers of the barrier had planned
for higher sea levels, not because of rising seas
but because southeast England is literally sinking
at a rate of 1.5 millimeters,
or a 1/16 inch, per year.
-The designers and engineers who crafted the barrier
made their best estimation and calculations to factor in
sea level rise in the future, not thinking of it
in the context of climate change or adaptation
but recognizing that the geological formation
underneath the southeast in London is sinking.
Their appreciation of geology
more than the appreciation of climate change
is what led them to put, in effect,
an 8-millimeter factor of safety every year
into the design of the Thames Barrier.
If you have a rising sea level in addition to a landmass
that is sinking,
that's a quite interesting combination.
-Climate change is now seen clearly
as a present and future threat.
In London, a dramatic 2013 weather event
exposed vulnerability
in the celebrated Thames Barrier system.
On December 5, 2013,
Cyclone Xaver smashed into Britain's east coast,
churning up the North Sea higher than in decades.
-In the northern parts of the UK,
the 5th and 6th of December
actually had higher sea levels than in 1953.
-The storm surge rushed up the Thames.
The barrier held strong and did its usual job.
-And that really was the most significant event
we've had since 1953, so that was a good test
of the sort of protective capabilities of the barrier.
-But in that storm, something new happened.
[ Rain pouring ]
Torrential rain filled the length of the Thames
with an unprecedented volume of water.
-The rainfall flow just didn't stop for 3 months.
-We have storm after storm tracking across the Atlantic
dumping hundreds of millimeters of rain on the UK,
so large regions experienced levels of rainfall
that we've not got in the observational record.
-The UK had more rain that winter than in any year
since records began in 1910,
and all that rain...
had to go somewhere.
-The River Thames is big, one of the UK's biggest rivers.
It's a catchment that we call it.
Any rain that's falling around that area
always goes down into the River Thames.
-By January, England was seeing a new kind
of flooding called fluvial.
The Thames was flooding, not draining, the land.
Now the barrier is put into action
in a way its designers never intended,
not to keep storm surge out of the Thames
but to use the river above the barrier
as a reservoir for excess rain.
At low tide, the barrier is closed,
leaving the Thames nearly empty to take on
flooding from heavy rainfall upstream.
-We've got two factors, rainfall going one way,
tide going the other,
and what we're able to do is close the barrier
and stop the surge tide from going into London.
If we close the Thames Barrier very shortly after low water,
what we end up in the center of London
is like an empty reservoir,
so the rainfall is able to come in and not cause any problems,
and the barrier is shut,
and with all the other defenses being closed as well,
they're able to contain that surge tide
and thereby stop from going into London
and therefore also not overflow, so we've done a double act
of the reservoirs contain the rainfall,
and the defenses and the barriers contain the surge,
so it's that act of looking after both sides, shall we say.
-Without the barrier's use, Central London
would've suffered catastrophic flooding,
♪♪
and there was a limit to how far the barrier
did work that winter.
In places like Sunbury on the Thames
just south of Heathrow Airport,
the water had no outlet, so it overflowed its banks.
[ Indistinct conversation ]
-We watch it coming up,
creeping up the bank slowly and steadily,
and once it breaks this bank, you know it's going to --
It goes very fast because once it's over this brow,
it starts to take the part very quickly,
and the you know you're going to be watching it
for quite a few days.
-In a matter of days, the Kirbys' home is underwater.
Tina, her husband, Adrian, and daughters
Sujata and Sujaza decide to stand their ground
as the waters rise right to their front door.
-Three weeks to a month, it was here.
It was around the house. We were --
We would have to wear waders to leave the house.
-Use a boat. -Then we started using a boat
to leave the house.
-It's creating a lot of mess and not going anywhere.
-We would take the children out in the boat,
you know, and sail them down the road.
You would try and make fun where you could.
-Yeah, because if you, you know, didn't have a laugh,
then you'd probably cry, but it was better to be at home
than to find yourself alternative accommodation.
-After nearly a month,
the Kirbys thought they had won the battle.
-Towards the end of January,
it started to recede, and so we thought,
"Okay. The worst of it's over, and things would be better."
It then started to rain again really heavily.
[ Rain pouring ]
The second time it came,
it came a lot faster.
-Now the water came higher and higher into the house.
-Probably about -- Was it about that high?
-Yeah, I'd say about nine inches --
-Nine inches... -...sort of maximum.
-...that, so it cleared the skirting
and was into the plaster.
-For more than a month, the Kirbys lived
with water nine inches deep in their house.
-And we thought, "It will be one night.
It'll go away, and we'll dry it out.
We'll get dryers, and it'll be fine,"
but, you know, wearing Wellington boots
in your house, you put them down,
and they float away the minute you put them down,
so every time you took your shoe off to go up the stairs,
you had to make sure you held onto it.
Otherwise, it would be gone,
and you'd be left standing there with nothing.
-That is the moment that you evacuate,
when you get a cold Wellington boot.
There's no way of drying it.
It's so cold.
That's when you go.
-Across southwest London,
families were flooded out of their homes.
In total, over 10,000 properties in the UK
were flooded that winter.
Even in Central London, which escaped flooding,
the defense systems were stretched to their limits.
-It was absolutely unprecedented in that
we actually had 50 closures of the Thames Barrier.
41 of those were as a consequence of the rainfall
with the remaining nine as a consequence of the tides.
Now, to put that into context, the normal operation
is of the order of about one to two per year,
so at that time,
we'd only closed about 160 times in 30 years,
so we saw a third of our closures roughly in three months
by comparison to 30 years.
-With their prized barrier working far more
often than it was intended to,
London's future against the rising Thames
is once again uncertain.
-The flood barriers have made a difference,
both the permanent ones and the temporary ones,
but it's clear, in some cases, they've been overtopped.
They've been overrun, and so, of course, we should look again
about whether there's more we can do.
-London has been here for many centuries.
Currently, we have a population of eight million.
By 2100, that could almost double,
and yet everybody wants to live in the center,
so we're building taller.
We're densifying, and we're building more subways,
more tube systems, and we're going down,
so when the rain falls, where does it go?
So we need space for water.
We need space for it soak to be able to be stored.
-With heavier and more frequent rainfall,
there is nowhere for all the water to go.
What's happening has as much to do with urbanization
as climate change.
Governments and public utilities are searching for solutions,
large and small.
-Things like gardens and parks
have been paved over for a variety of reasons.
There's more runoff, and it's more likely to cause
flooding than perhaps a generation ago
when there was just more greenery around to soak it up.
-15% of Greater London is considered
to be the floodplain,
most of it in the low-lying areas alongside the Thames
where approximately 1.5 million people live,
and more are still coming.
About 75% of this massive urban area
is completely paved over.
With so much of the absorbent green space
covered with asphalt and concrete,
the runoff is directed into sewers and drains,
which can't handle that excess water.
-It's running off into very old sewers that were built back
in Victorian times for a whole different population,
but they're too small, simple.
I feel we have been put to the test.
I know that this area is a floodplain, for instance.
They're still building many flats.
You know, people need accommodation.
I don't know what they're doing when it comes to the flood risk.
The Thames Barrier is not that far away from here.
I have this place because it's affordable.
The end of the day, it is in a floodplain,
and I know it's in a floodplain.
What do you do?
-London needs new solutions against the increase in rain.
The first challenge is better prediction of future rainstorms
like those of 2013-2014.
-When '13-'14 came along
and we had such unprecedented levels of rainfall,
then the immediate question arises, where did it comes from?
-Professor Adam Scaife is the head
of long-range prediction at the Met Office,
the UK's national weather service.
He says climate scientists have long known
that global warming will lead to increased rainfall.
-Something called the Clausius-Clapeyron Equation,
it's a really simple equation.
People study it at school, tells you that,
the warmer the air, the more moisture it will hold,
and therefore, when that moisture comes out,
which it must do somewhere, then you will have heavier,
more frequent downpours
and more mean rainfall, so that's really clear.
We know that.
The big question is, where?
Where is the rainfall going to come out?
And that, of course, is much more difficult.
-Traditional weather-prediction tools like satellites
provide part of the picture,
but long-term forecasting has to account for additional factors.
-You better take into account the increasing CO2
because the temperature is going to be that much different.
However, if you want to forecast very long range beyond,
say, a week, the ocean starts to play a really big role,
and so we have something called Argo floats.
There are thousands of these things all over the globe.
It's an international project.
We put them all together, collect all the data,
and that tells us what the temperature and salinity
of the ocean is throughout its depth worldwide.
The ocean is a bit like a pacemaker for the atmosphere.
The atmosphere is jumping around
with its weather storms and things,
but the slow guiding force of the ocean
can steer that chaotic variability one way or another.
-All of that data is compiled
onto one of the biggest supercomputers in the country.
-It allows us to split the globe
into tinier and tinier pixels,
and the more pixels we have and the more layers
we represent the ocean and the atmosphere over
and the more accurate we can get the forecast.
-That allows Scaife to narrow down
how the rainfall will affect the specific area.
What the computer's results show is bad news for London.
-We are very confident that, in winter,
we're going to see more rainfall, more heavy rainfall
and more average rainfall and hence more flooding.
There is, every single winter,
between 5% and 10% chance of a new record.
Then, after a few decades,
what is now an unprecedent event will become the norm.
-The Thames Barrier was designed to be used
just a few times a year.
If it's needed 50 or more times as it was in the winter of 2013,
it will wear out.
That is a mechanical certainty.
-You know, similar to your car, if you're always driving
your car, you're never going to be able
to put it in the garage to maintain it,
so there's got to be an optimum figure,
and notionally, just for now, we've put that as 50,
so we're working towards when we hit that maximum of 50 per year,
we would need to have a new barrier.
-And that's without factoring in the next big problem --
sea-level rise.
London has to plan for how much sea level
will rise by the end of the century.
One estimate predicts that could be from 10 to 35 inches.
-Based on the acceleration rates we're seeing
at the moment, we think it's going to be
at least 50 centimeters if not higher,
but we're expecting with an acceleration in ice melt
that, that will gradually increase,
so for London, the maximum we think it could be
by the end of the century is about 2 1/2 meters.
That's the physically plausible upper, upper rate.
-That's 8 feet of sea-level rise.
The UK Environment Agency,
the government body tasked with flood protection,
recommended the barrier's life expectancy
be extended from 2030 until 2070 to buy time.
-Within the original design criteria for the barrier,
there was enough allowance to actually mean
that we've got another 40 years
of that high degree of protection
but ease more life out of it.
-But that was before the winter floods of 2013
increased the barrier's workload so much.
More rain and rising seas
will put still more strain on London's infrastructure.
-You could get such a severe weather event
that we've never seen before in this country.
It could overwhelm our defenses.
-Even the best-designed engineering solutions
can't last forever.
All of London's current defenses
will soon need upgrading or replacing.
-Whether it's the barrier, all the walls
in the center of London or out to the estuary,
you're daft if you don't think things have a life.
You're daft when you don't plan for all them coming to an end.
-Increased and more intense rainfall,
a massive mostly concrete city surface,
an aging, overused barrier system
for the mighty but dangerous Thames River and rising seas
increasing the destructive power of storm surges.
The UK is bracing itself for the 21st century
with an array of solutions,
some low-tech, some among the most advanced in the world.
♪♪
This is the state-of-the-art Flood Forecasting Centre.
Senior Team Leader Brian Vinall
and his group are armed with satellites,
radar and coastal gauges
that give them up-to-the-minute information.
-We have a lot of data,
and we have some very, very highly trained staff.
They're the ones that have that decision
as to whether to ring me
and wake me up at 3:00 in the morning to say,
"We need to start briefing government."
It's up to them to decide what the response is.
We tell them what the risk could be.
We try and say how many properties might flood.
We try and put it into context about,
"This could be as bad as 1953."
-The prime goal of Vinall and the Flood Forecasting Centre
is to make sure evacuation orders
are given early enough to save lives.
-We're not going to be able to tell an individual house
whether they're going to flood in four, five days' time.
What we can do is tell the emergency responders
that there's probably going to be a community
affected in this area.
Now, you do get accused of cry wolf with that.
You do get people who could potentially by evacuated
and have no flooding happen.
I'd much rather have that on my conscience.
-Water is hitting London from all sides.
The problem here is getting it out.
-An awful lot of flood risk management
is about moving water around to places or holding water up
in places where it won't harm people and property.
Where everywhere is under the water,
then you start to have quite limitations
on what you can do about it.
-The government has a massive plan
to tackle climate change this century.
TE2100 is the blueprint for keeping London
from going underwater.
The Thames Tideway Tunnel is one of London's
most ambitious and expensive plans.
It's a massive initiative designed to channel the water
from overflowing sewers before it gets to the river.
200 feet below the Thames
and running along roughly the same path,
it's a £4-billion project that will take seven years to finish.
-At the turn of the century here in London,
the Victorian civil engineers
were some of the earliest pioneers
in providing fresh water and sanitation
below the heart of our city.
Now, that envisaged a certain quantum of population,
but that has grown tenfold, twentyfold.
-Managing the sewage network for 15 million people
is obviously a massive challenge.
-Rob Sainsbury and Pascal Lang are with Thames Water.
The sewer system they oversee, run end to end,
would stretch halfway around the world at the equator.
-We're trying to make it as resilient as possible,
but obviously there are times when we have extremely
heavy rainfall where the system can't cope.
-Many of the sewer lines carry channels
for both sewage and storm water, which is now a serious problem.
-If we have a combination of rainwater and sewage,
our sewage reaches capacity,
and then that sewage then spills out of the manhole.
If people are coming into contact with that sewage,
that's obviously a public health concern.
-The current sewer system was constructed
in the late 19th century.
It was designed principally to service 4 million people,
and because of the way sewer systems are built,
it's very difficult to retrofit them and upgrade them over time.
-A fail-safe is a backup mechanism
for when a system doesn't work,
and in the case of London's flooding sewers,
the fail-safe was overflow into the Thames.
This unsanitary solution of the Victorian era
still happens today,
and it's a major health problem London urgently needs to fix.
-So you have sewage going directly into the Thames.
You have water quality going down.
At the same time, you have all the water runoff in order for it
not to flood or it to be backed up in the system
actually going down into the River Thames.
So that happens 50 times a year.
-One goal of the Tideway Tunnel
is to upgrade this antiquated system
and ensure raw sewage no longer gets into the Thames
by diverting the contaminated overflow
to upgraded treatment facilities.
-The Tideway Tunnel is London now getting its act together
and trying to find a way to deal with this old sewer system.
It's a tunnel 25 kilometers long,
which lies across the London Basin of the Thames.
Its function is to allow for all the water runoff
that comes from the draining systems,
in addition to the sewage, to be discharged into the sea.
It's so expensive now to dig underground in London.
People are put off because of the price tag.
So in the future, unfortunately we'll be forced to use it,
whether we like it or not,
whether we like the price of it or not.
-The Tideway Tunnel
is projected to be finished in 2023.
Meanwhile, London has other mega projects
planned for the Thames.
-The T2100 is looking at improving all the flood
defenses along the Thames estuary
to improve both the riverbank,
the embankment, the floodwalls and the seawalls
and the coastal defenses that are in the estuary itself
to then allow the barrier to carry on functioning
until 2080 where the idea is
that they will want to build a second Thames barrier.
-Rather than building a new barrier now
that's going to cost billions,
they said, "Let's delay the procedure."
There's some things that they can do
to extend the lifetime of the barrier.
They can slightly overclock the gates.
They can build and use sort of defense schemes
in and around the barrier.
If sea level rise starts to accelerate
and gets much higher than that,
then obviously we've got to go down a different pathway.
Now, the problem with this approach is
it assumes that you can detect
when sea levels are accelerating,
and certainly with the original Thames barrier,
it took 30 years to build,
so there's a very long lead-in time.
-Considering that lead time, the Environment Agency needs to
make sure they have a clear picture of sea level rise.
They've enlisted researchers like Dr. Ivan Haigh
to make sure they have the most accurate data.
He observes fluctuations in sea level rise
that may not be related to climate change.
Some are part of natural annual patterns in the North Sea.
-Sea level doesn't just rise smoothly and gently.
Every year, sea levels rise as the ocean warms up
in the summer, falls as the ocean cools down,
so we can see every year its rising-falling.
-He collects data on other factors involved
in that fluctuation like temperature,
salinity, wind and atmospheric pressure.
He has to work out what is caused by climate change
and what isn't.
-The way I tend to picture it is,
imagine you're at a party.
There's 10 people in the room.
Everyone is talking.
Some people are talking very loud.
So sea level is very noisy.
The acceleration component is a small, quiet voice.
So what we found is, when we're able to remove
90% of the noise, we do now see a very clear
statistically significant acceleration signal.
Over the 20th century, we saw about 1.7 millimeters per year.
Now, in the last few decades, we're starting to see double
that rate -- about 3 millimeters per year.
For the first time in the UK now,
we are detecting that the rate is getting faster.
-London's TE2100 plan is tackling rising seas
and increased rainfall
with multi-billion-dollar infrastructure projects
and with small-scale solutions.
This project is called Sustainable Drainage Systems
or SuDS.
Kevin Barton is a landscape architect working on SuDS,
a localized approach to drainage becoming popular in London.
-The problem in London, much like many cities
around the world, is, over the centuries,
we have paved over large parts of our landscape.
We've created this impermeable barrier over our landscape,
which means that when it rains,
what we see is much larger volumes of water
entering our sewer systems and eventually into our rivers.
Plus there's none of the slowing of that water that nature gives.
-The problem when the rainwater falls
is that sewers reach capacity.
Then they overflow into basements or onto street level,
and of course with sewerage, it's foul waste,
so it's contaminated, which is even worse.
-Jessica Bastock is the flood risk manager
for Hammersmith and Fulham, a riverside district in London
that is almost entirely paved over and prone to flooding.
-So what we're trying to do here
is to stop that from happening
by relieving the pressure in the sewer
and actually dealing with water,
the rainwater that falls on the ground, sustainably.
-SuDS offers a range of drainage solutions
depending on the site. -This is Mendora Road,
and along Mendora Road, what we try to do
is use permeable-block paving to deal with water.
All that is, is block paving,
but instead of it being butted together,
it's actually open, so water can flow between the blocks,
and that means that when water falls,
it runs through the block paving and gets stored underneath.
We're on Bridget Joyce Square.
Along this stretch of road now,
there are multiple SuDS features.
On this side of Bridget Joyce Square,
we have permeable-block paving.
In between the blocks, there are little gaps,
and rainwater that falls on the surface
actually moves through these gaps
and then into a detention basin.
♪♪
When the basin starts to fill up during the intense rainfall
event, there is an overflow point,
so it will go back into the sewer system,
but it will go at a really slow rate,
so it will be a trickle.
On this side of Bridget Joyce Square,
we have a local school.
To incorporate this school into the design,
what we've done is, we've taken the rainwater
from the school building, on the roof,
and we've disconnected the downpipes,
which would normally have fed into the sewer system,
and we just channel it across, and then through little holes,
that actually feeds straight, directly into the basin.
-Another SuDS scheme has been implemented
about a mile away on Goldhawk Road.
-This road, it's very, very busy,
so in this kind of situation, what we've had to do
is to have a sustainable drainage measure
which can fit in this landscape.
Engineered tree pits were thought
to be the best way forward.
They collect water from the carriageway,
and then they feed into the drain here,
and then this is like a lateral drain, so a flat drain,
and it feeds straight into the base of the tree pit here,
and then underneath this tree pit
is lots of box-crate storage, which holds water.
-Kevin Barton believes SuDS
will be commonplace across London by 2100,
incremental steps with a big result.
-Feels like we're on a steep curve at the moment
where more and more people are coupling onto SuDS.
When you understand it saves money,
it's good for developers as well as the environment
and as well as flooding.
From everyone's perspective, SuDS is a no-brainer.
-SuDS are good, but they're a soft solution.
The difficulties in Thames is that,
if you have a flash flood incident,
and it rains, and there's a large amount of rain
in a short period of time,
that in itself becomes an impervious surface.
SuDS aren't able to deal with that type of water runoff
whereas a sewer system can, specifically the Tideway Tunnel.
-As London looks to the future,
it also looks to the past for overlooked options.
-By the mid-19th century, most of the tributary rivers
would become effectively open sewers,
and they were heavily polluted,
and they were faced with a public health crisis.
Their response was to bury those rivers,
pipe them up and build over the top of them.
It also created more space
because they could be built on top of,
so it made way for development.
-The project, run by David Harding,
revolves around a network of lost rivers
that lie beneath London.
-London lost about 26 of its major tributaries,
rivers like the Fleet and the Tyburn and the Walbrook.
There were lots of cases where we were investigating
flooding in the urban area
where we couldn't really account for where all the flow came from
because those rivers still do function
as rivers when it rains.
-And that's at the heart of many of today's
flooding problems in London
and other global cities built over rivers.
-So what we've got to do now is to start to restore
some of the more natural drainage of London.
Rather than wait for these water courses
to reveal themselves when they flooded,
go out and look for them proactively to understand
where all the rivers have disappeared to.
We start off from the LIDAR mapping,
the digital terrain mapping, to look for telltale signs.
The blue is the highest ground going down to the yellow,
which is the lowest ground,
and you start to see what looks like a floodplain
or a river valley with networks of tributaries coming off of it.
We then start to refer to the historical mapping.
So taking one of those potential
flow pathways from the LIDAR data
and referencing it to a map from 1846,
you can start to see that the Salmons Brook is actually mapped
when it coincides very well with the LIDAR data,
and at this stage in the urbanization,
the river was still on the surface.
-Guided by high-tech data,
he takes the search from the office to the field.
Harding is in a suburb of London where he hopes to find traces
of the city's Victorian shape and structure.
-So we're on Nestor Avenue now where we believe
that the Houndsden Gutter,
a lost watercourse, flows to my left.
If you put a river in a pipe or a channel,
it's got a finite capacity,
and when that capacity is reached,
then that's when you start to get flooding
coming out of things like manholes,
flooding into properties and gardens and roads
as opposed to the natural watercourses,
which could flood out on the floodplains,
which, in many cases, are still there.
So if we could daylight some of these watercourses in the areas
where they can be allowed to safely flood,
then that reduces the flood risk to the built-up area.
-Daylighting means opening the river back up
to its natural state,
giving the water more room to flow,
but since they've long been covered over,
these rivers have disappeared from modern maps.
-Okay, so the map has led us to the open section
of the watercourse that's to my left,
and there should be a pipe or a tunnel linking that
to the next visible open section of watercourse,
so we're just going to go down into the river now
and walk the river and look for the existence of the tunnel.
♪♪
-Harding discovers that his software correctly identified
the existence of a buried section of river.
-This conduit that was built when the road was built,
when the houses were built,
this was just a way of putting it in a nice,
straight line that was out of people's way,
and it's typical of thousands of kilometers of ordinary
watercourses across London.
-Most of the people who live and work in these shops
and cafes have no idea a river once ran through their community
and may soon be flowing again.
-There's no reason why they couldn't be restored
to a more natural river corridor.
Now that we know it's here,
we can understand any upstream flood risk that's caused
by the throttling effect of this tunnel,
and we can then look for opportunities to allow the river
to spread out into safe open areas.
-So far, over 11 miles of lost rivers in London
have been daylighted.
♪♪
One of the best examples uses landscaping with earth
bunds or embankments here
at the Firs Farms Wetlands in Enfield in north London.
♪♪
-We identified that using Firs Farm as a flood storage area,
we could protect quite a significant number
of people living downstream.
We realized that instead of building a concrete wall,
we could build a natural earth bund as a defense
and to generate the spoil that we needed to build that bund,
we could carve out a channel,
and that channel has now become the restored river.
-Though the wetland is about 12 miles from the center of London,
the project is already having an impact,
reducing the amount of rainwater flowing into the Thames' system.
-And we realized that using wetland planting,
we could mitigate the urban pollution.
You can actually clean that water by passing it
through a filter bed system.
We've ended up with a combined wetland
and flood storage area here,
and by combining those two things,
you get multiple benefits.
You've got the permanent habitat, which is always here --
the wetlands and the plants and the wildlife and so on.
You've got an area that local residents can come and visit
and enjoy on a day-to-day basis,
but you've also got a functional landscape
which actually stores tens of thousands of cubic meters
of water during intense rainfall
and protects people living downstream.
-Harding sees this kind of organic approach
to flood prevention as a necessary complement
to large infrastructure like the Barrier.
-The scale of hard engineering that's needed
to start to address flood risk through climate change now
is becoming unfeasible, you know?
We can't go for the big-tunnel solutions forever,
so we need to start sort of rolling back
some of the urbanization and sort of managing flood risk
in a more natural way like this project does.
♪♪
-Another more radical solution is not to battle the rising sea
but to work with it.
Richard Coutts is an architect and urbanist
specializing in floating architecture.
-London is particularly under threat through climate change.
We have sea level rise, and we're seeing more rainfall.
We are building more, and the upshot of that is
there's just not enough capacity in the system
for this rainfall to go.
To meet those challenges, we need to use the water space.
We need to inhabit.
We need to optimize our resources.
Casting our minds forward to the next 50, next hundred years,
one could imagine London thriving at the water's edge,
new communities just growing, inhabiting the water space,
the parks, new homes, businesses right in the heart of cities.
-And Richard's secret weapon?
-And we're looking at floating communities.
We've actually coined the phrase "aquatecture,"
which is essentially architecture on water.
So we're currently located in the Royal Docks of London.
We are in a floating hotel.
This was constructed in the turn of the 19th century.
The Good Hotel is unique in terms of its thinking.
It's a traditional industrial unit on a floating base.
This was formerly a prison building
that was birthed in Amsterdam.
It was no longer fit for purpose,
and this is one of the wonderful things
with floating architecture -- it has flexibility.
You take it somewhere else.
You give it a fresh lease of life,
and from a building which previously people
were fighting not to get in, we're now in a situation
where people are paying a premium to dwell,
to rest right on the water's edge.
-Aquatecture is design that combines with water
rather than resisting it.
It's something Coutts believes
is a solution in London's future.
-And we're looking at the existing communities
and how to make those resilient.
We're looking at stilted houses and amphibious dwellings,
and then at the other end of the scale,
we're looking at floating and flood-resilient communities.
This is the UK's first amphibious house,
and it's built 8 meters from the River Thames
and is a house which is designed to rise and fall with the water.
This is more of a practical approach,
which allows the people who live here to be within their garden
and to be low,
but in the event of a flood, the house is more responsive.
The benefits of an amphibious house are,
in the event of a flood, the house can float.
It can literally move up and down.
The garden is designed as an early-warning system,
and what we've got is a series of tiered plains
almost like buckets.
When the first two fill,
it actually triggers the buoyancy of the house.
-Architecture that works with rather than against the water
is an idea being considered
by designers and engineers worldwide.
Coutts believes that floating structures will be embraced
by the world's most powerful players.
-Floating cities, those cities which really grow,
those which are at the forefront will be those that utilize water
in that adaptable fashion to bring in a floating Olympics,
to bring in those floating expos,
to providing housing, to meet the needs of their workforce
in the middle of the city,
and water provides that opportunity.
-For decades, London trusted the Thames Barrier
would keep it safe from water.
Now, that sleeping giant can no longer be relied upon
as rainfall increases and sea levels rise.
-You know, the risk to London is huge --
1.25 million people, £375 billion worth of infrastructure.
You know, there is 400,000 properties.
You can just keep on going with the stats.
We can't fail.
We've got to get this right.
-Still, the people of London aren't feeling
as safe as they once did.
-I think, if it rains for more than three days in a row,
I start thinking,
"Is this going to be another one of those winters
where we start getting rain after rain after rain?"
-The city's search for multiple solutions continues.
-I think that sort of the approach
that the Victorians took,
that, you know, you could always throw enough technology
and enough concrete at a problem,
and you could overcome it,
but, you know, there's an acceptance
that that's not appropriate in all circumstances,
and a more natural approach to flood risk management
is the only one that's going to be sustainable
in the face of more severe weather,
rising sea levels, you know, more prolonged wet periods.
-We need clever architects,
designers that can build cities that can cope with sea levels
and almost make that part of the future design of the city.
-The challenges are immense, as are the stakes,
but London is ready for the battle.
-In London, we need to make a few decisions.
You can see we have some wonderful heritage,
and we need to protect and defend that,
so maybe in these areas, we maintain our flood defenses,
but in other areas of the city,
we need the capacity in the system for this volume of water,
and we may have to consider retreating,
taking down some of those buildings,
creating parks to provide additional storage.
We can still use those as recreation,
but we need to think more intelligently.
We need our policy makers to keep up,
to be with us on this journey
as we deliver this very innovative infrastructure
and new ways of living to enable our cities to grow.
-So right now, the biggest challenge
is to let planners, policy makers,
the people who make decisions understand
that we have to actually streamline these systems
so they can function as one, and I think that alone
is a big challenge of what London needs to do
to move into the 21st century in its foremost.
So adaptation challenges our current way of thinking.
It challenges everything we think we do and say
and based not in the name of sustainability
but in the name of resilience.
-Well, even for wealthy cities, this is going to be a challenge.
They're going to have to watch this very carefully.
It's going to require
a significant amount of investment.
That investment will be an increasing proportion
of the economic activity in that city,
and this is going to be the issue for the 21st century
around a number of coastal cities.
♪♪
Narrator: Next time, Miami is considered the most at-risk city worldwide
due to rising sea level and storm-related flooding.
We're gonna get probably 2 feet of sea-level rise by 2060.
Then, by 2100, we might get 6 feet of water.
The water is coming.
We already see 20 days a year
that, just high tide, the water is higher than the land.
Man: Water is coming from the side, from below, from above.
Miami is at that point where they've got to decide,
"How do we solve the issues of sea-level rise?"
♪♪
-To order "Sinking Cities" on DVD,
visit Shop PBS or call 1-800-PLAY-PBS.
This program is also available on Amazon Prime Video.
♪♪