1.
Case Study for Flooding
Storm Surges
Storm surges are sudden rises in
sea level caused by very strong winds, normally those found in hurricanes and
cyclones. The strong winds essentially push the water on an ocean’s surface on
top of more water, increasing the sea level and flooding coastlines. The
conditions needed to create these strong winds are generally associated with
low pressures, further increasing the sea level. The strong winds can create
large and powerful waves that can overtop coastal defenses so even if the rise
in sea level doesn’t flood the coastline, the resulting waves likely will.
Logically, storm surges are most
dangerous during high tides, since
the sea level will already be elevated at this time.
Rising Sea Levels
As sea levels rise due to climate
change or isotactic rebound low lying coastal areas are permanently flooded by
the sea. The likelihood and severity of storm surges also rises since weaker
winds will also be able to increase the sea level enough to flood coastal
areas.
Tsunamis
Tsunamis are giant waves
resulting from earthquakes, volcanic eruptions, meteor impacts, any sort of
major displacement of water in the ocean. Tsunamis are incredibly dangerous
since they travel quickly and are difficult to detect. Out at sea, close to the
source of the tsunami, the amplitude of the wave is relatively low making it
difficult to detect but it travels very quickly (over 800kmh-1). As it
approaches the shore the wave slows down significantly but its amplitude
increases exponentially without the wave breaking. When the wave hits the coast
it does so with an immense amount of energy and its amplitude continues to grow
as it slows down even more. Tsunamis have so much energy that they can travel
several miles inland.
Tsunamis flood vast expanses of
land and cause immense amounts of damage due to the energy they impact the
coast with and the fact that they collect debris as they inundate more areas.
Reclaimed Land
Many coastal settlements have
developed onto what is known as “reclaimed land”. This is land that has been
gained from the sea due to coastal management or, somewhat ironically, lowered sea levels. This land, while highly
valuable, is low lying and flat, so a small rise in sea level from a mild storm
surge is enough to flood it and cause extensive damage.
March 2011 Tōhoku Earthquake & Tsunami (Japan)
On March 11th 2011, a magnitude 9.0 earthquake
occurred with an epicentre that was around 70km from the Tōhoku region of
Japan. The earthquake displaced water in the Pacific Ocean by nearly 6m
creating an incredibly powerful tsunami that devastated the eastern coastline
of Japan. The first wave of the tsunami took around an hour to reach the
coastline and flooded Sendai airport. From this point, several waves impacted
the coast with heights ranging from 3m to 20m in different areas around Japan.
The height of the waves was predicted to be between 3m to 6m. In the city of
Sendai, the tsunami flooded land 10km away from the coast.
Social Impacts
•
The tsunami killed
thousands of people. The National Police Agency has stated that the death toll
from the earthquake was 15,870 deaths of which 14,308 people drowned. Many more
people are still missing. In the town of Minamisanriku, 10,000 people went
missing.
•
The tsunami wiped entire
towns off the map, destroying communities and uprooting & separating
families. Out of 100,000 children who were forced out of their homes, many of
them were separate from their parents.
•
Because of the large number
of people killed, mass graves had to be dug for the dead as morgues and
crematoriums were over capacity and damaged. With no where to preserve bodies,
they had to be buried before disease started to spread.
•
Over 700 cultural relics
were destroyed by the tsunami and many museums and libraries were flooded.
•
A level 73 nuclear meltdown at the Fukushima Daiichi power plant
resulting from the tsunami forced 1700 people to evacuate their homes in the
area surrounding the accident. They will not be able to return to their homes
for a long time since they have been contaminated with radioactive materials.
Economic Impacts
•
Through a combination of
the tsunami and earthquake (with the tsunami doing most of the damage) 45,000
buildings were destroyed and 145,000 were damaged. The estimated cost of the
disaster is in the tens of billions of dollars.
•
Industry was heavily
disrupted due to power cut outs caused by the loss of a power plant, the
severing of electrical pylons and the loss of oil due to a fire at an oil
refinery.
•
Some of the worst affected
areas by the tsunami were ports and fishing villages. 319 ports were damaged by
the tsunami and had to be closed some for up to a year. The tsunami caused some
¥1.3 trillion in damage to the fishing industry in the areas affected by the
tsunami.
•
Most people who owned homes
did not have earthquake or tsunami insurance and so will have to pay for
repairs or reconstruction of their homes themselves or through government
assistance.
•
24,000Ha of farmland was
destroyed by tsunami. The presence of salt on this farmland will make it
un-farmable for many years now.
Environmental Impacts
•
The tsunami washed tonnes
of debris out to sea including wooden planks, metal, cars, boats and oil.
Debris has been found on coasts around the globe and pose risks to sea life and
animals that live along coasts.
•
The nuclear meltdown at the
Fukushima Daiichi power plant has released unknown but dangerous amounts of
radioactive material into the atmosphere and water nearby the power plant. Food
that was grown in Fukushima has now been banned because it was found to contain
high levels of radiation.
•
The meltdown will have
environmental impacts globally since the radioactive materials have entered the
atmosphere.
Responses
•
In the immediate aftermath
of the earthquake, a tsunami warning was broadcast that allowed people to get
to higher ground. The tsunamis were taller than predicted though and many of
the safe zones weren’t safe.
•
Urban search and rescue
teams and the Japan Self Defense Force carried out search and rescue operations
in the areas affected by the tsunami and earthquake.
•
The Japanese government
requested assistance from South Korea, New Zealand, Australia, Germany, the USA
and the UK and also made satellite data, showing the extensive damage caused by
the tsunami, available to all relief efforts.
•
The Japanese Red Cross
received $1 billion in donations and the American Red Cross received $120
million in donations towards their efforts in Japan.
•
Nuclear engineers from
around the globe assisted the Japanese government in attempting to avert a
nuclear meltdown at the Fukushima Daiichi plant.
•
Temporary housing was set
up for those who lost their homes. By June 2011, 46,000 temporary homes had
been set up and 20,000 people were staying in inns or hotels.
•
In the months following the
disaster, the government set about rebuilding the many sea walls that had been
destroyed by the tsunami and also increased the height of the sea walls still
standing.
•
Efforts were made to
understand why the earthquake and resulting tsunami had been so powerful so
that future earthquakes of a similar scale could be prepared for.
1
That’s using the moment
magnitude scale, not the Richter scale.
2
The Tōhoku region is
located in the north east of Honshu, the biggest island that makes up Japan.
3
That’s the highest level
you can get. The only other accident to get this level was Chernobyl in 1986.
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