NATURAL

HAZARDS

TOPIC TWO

We will be focusing on...

Page

What are natural hazards? 3

Natural hazards vs natural disasters 6

Risks of natural hazards 7

Flooding 8

Wildfires 16

Sandstorms 23

Avalanches 27

Hurricanes 29

Blizzards 32

Research task 36

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What are Natural Hazards?

Natural hazards are extreme natural events that can cause loss of life, extreme

damage to property and disrupt human activities.

The following pictures show different types of natural hazards.

Can you name them all?

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A natural hazard is an event which has the potential to cause loss of life or

property. Without people, it is just an event and not a hazard. The interaction

of people make it a hazard!

Natural disasters are events caused by natural hazards, which in turn cause a

lot of damage to humans and/or the environment.

The damage caused varies, depending on how severe the natural hazard is.

Example of a Natural Hazard:

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Example of a Natural Disaster:

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Natural Hazards vs Natural

Disasters

Natural hazards can have economic, social and environmental consequences.

For each hazard event the risks, or probability, of a particular consequence

occurring can vary greatly.

This depends on certain factors. For example in a developing country, the death

toll tends to be high but the short-term economic costs are often relatively low,

whereas in a developed country, the death toll tends to be low but the short-

term economic costs can be extremely high.

The long-term situation is more complex. Developing countries can be slower

to repair damage to roads and buildings. This can lead to a reduction in tourists

and therefore a long-term loss of valuable income.

Hazard risks are increasing due to population growth, urbanisation, pressure

on marginal land and changes to the natural environment

Risks of Natural Hazards

Flooding is a natural event where an area of land that is usually dry land,

suddenly gets submerged under water. Some floods can occur suddenly and

recede quickly. Others take days or even months to build and discharge.

When floods happen in an area that people live, the water carries along objects

like houses, bridges, cars, furniture and even people. It can wipe away farms,

trees and many more heavy items.

So... what causes a flood?

Flooding

These are a few events which cause flooding...

RAIN

Each time there are more rains than the drainage system can take, there can be

floods. Sometimes, there is heavy rain for a very short period that result in

floods. In other times, there may be light rain for many days and weeks and can

also result in floods.

RIVER OVERFLOW

Rivers can overflow their banks to

cause flooding.

This happens when there is more

water upstream than usual, and as

it flows downstream to the

adjacent low-lying areas (also called a floodplain), there is a burst and water

gets into the land.

STRONG WINDS IN COASTAL AREAS

Sea water can be carried by massive winds and hurricanes onto dry coastal

lands and cause flooding. Sometimes this is made worse if the winds carry rains

themselves. Sometimes water from the sea resulting from a tsunami can flow

inland to cause damage.

DAM BREAKING

Dams are man-made blocks mounted to hold water flowing down from a

highland. The power in the water is used to turn propellers to generate

electricity. Sometimes, too much water held up in the dam can cause it to break

and overflow the area. Excess water can also be intentionally released from the

dam to prevent it from breaking and that can also cause floods.

ICE AND SNOW-MELTS

In many cold regions, heavy snow over

the winter usually stays un-melted for

sometime. There are also mountains that

have ice on top of them. Sometimes the

ice suddenly melts when the temperature

rises, resulting in massive movement of

water into places that are usually dry.

This is usually called a snow-melt flood.

ECONOMIC

During floods (especially flash floods),

roads, bridges, farms, houses and

automobiles are destroyed. People

become homeless. Additionally, the

government deploys firemen, police and

other emergency apparatuses to help

the affected. All these come at a heavy

cost to people and the government. It

usually takes years for affected

communities to be re-built and business to come back to normalcy.

ENVIRONMENT

The environment also suffers when floods happen. Chemicals and other

hazardous substances end up in the water and eventually contaminate the

water bodies that floods end up in.

Additionally, flooding has a very bad impact on animals as many animals end up

drowning in these floods. Insects are also introduced to affected areas,

distorting the natural balance of the ecosystem.

Floods can have devastating consequences and can have effects on the economy, environment and people…

PEOPLE AND ANIMALS

Many people and animals have died in flash floods. Many more are injured and

others made homeless. Water supply and electricity are disrupted and

people struggle and suffer as a result. In addition to this, flooding brings a

lot of diseases and infections including military fever, pneumonic plague,

dermatopathia and dysentery. Sometimes insects and snakes make their ways

to the area and cause a lot of havoc.

BUT...

There is also something good about floods, especially those that occur in

floodplains and farm fields. Floodwaters carry lots of nutrients that are

deposited in the plains. Farmers love such soils, as they are perfect for

cultivating some kinds of crops.

CASE STUDY

The Great Flood of 1993

During June and July of 1993, the Mississippi River basin in the United States

experienced very high rainfall which resulted in a disastrous flood. The flood

lasted for so long that many areas stayed flooded for weeks and other locations

of the river were in continuous flood for 6 months!!

What were the effects that this flood left behind?

Estimates of the total damage was $15 billion.

100,000 homes were damaged (50% due to groundwater or sewer

backup) while 10,000 homes were completely destroyed.

10 commercial airports were flooded and all railroad traffic in the

Midwest was halted.

20 million acres were flooded along the Missouri and Mississippi rivers.

The 1993 and 1994 harvests were lost.

Numerous sewage treatment plants were destroyed.

38 deaths were associated directly to the flood.

Many levees broke (as can be seen in the satellite pictures on the previous

page.)

Warm, nutrient rich water had resulted in hypoxic conditions in the Gulf

of Mexico

Out of the many natural disasters we have, wild fires would be one that is very

common, very difficult to fight, and maybe the most dangerous.

WHAT IS A WILDFIRE?

A wildfire is simply an uncontrolled fire that is wiping out large fields and areas

of land. These fires sometimes burn for days and weeks. They can wipe out an

entire forest and destroy almost every organic matter in it.

Wild fires can also be termed forest fires, grass fires, peat fires and bush

fires depending on type of vegetation being burnt. Note that these fires tend to

thrive in very warm and dry climates, rather than the thick, moist rainforest

types.

Wildfires

These people are camping in a forest. Can you identify any fire

hazards in this picture?

So what can cause a wildfire?

Think… What can cause a wildfire?

Causes of wildfires...

ECONOMIC COST

Fires do immediate damage to wildlife and vegetation. They can destroy

houses and almost anything in their way. Countries spends millions of money to

fight them with chemicals, logistics, aircrafts and trucks, time and personnel.

The economic loss can be huge.

SOILS AND ORGANIC MATTER

Forest soils are rich in decaying

debris and nutrients, and are

composed of many natural

features that support a huge

variety of life forms and organic

activities. Wildfires raise the

temperatures of these soils to

over 900°C and this potentially

wipes away almost all the organic value of the soil.

Effects of wildfires

WATERSHED

Burned organic matter in the soil also affect the natural layering of the soils.

This negatively affects infiltration and percolation, making the soil surfaces

water repellent causing soil to erode.

Researchers believe that forest fires are not all that bad, as they have some

benefits too.

In fact, they believe that even though young animals and birds may die, many

animals are able to escape or move away from fires. Birds fly away, dear and

other reptiles find their own escape routes and so on.

Many plants easily grow back and there is usually good recovery after a fire.

Some plants have their seeds opened up and exposed to ash-enriched soils.

CASE STUDY

The Mendocino Complex Fire July 2018

This wildfire was the largest recorded fire complex in California history. It was a

combination of 2 large wildfires; the Ranch Fire and the River Fire. Between the

2 fires, there was a total of 459,123 acres (1,858 km2).

What were the effects that this wildfire left behind?

Destruction of 280 structures and another 37 damaged.

$267 million in damages.

More than 10 whole communities had to be evacuated due to the impacts

that the fire complex had along the Mendocino and Lake County borders,

causing the evacuations of Lakeport, Kelseyville, Lucerne, Upper

Lake, Nice, Saratoga Springs, Witter Springs, Potter Valley, Finley, parts

of Hopland, and the tribal communities of Hopland Rancheria and Big

Valley Rancheria.

A sandstorm refers to a high amount of wind occurring in sandy areas, usually

in deserts, where the wind speed is able to lift the top layer of sand from the

ground, and push it in every imaginable direction.

What causes a sandstorm?

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How high can a sandstorm get?

The sand involved in the sandstorm can reach heights of approximately 10-50

feet (3.05-15.24m). Usually, the height of a sandstorm corresponds to wind

strength. Dust particles associated with some sandstorms have been found at

5000 feet (1524 m), though these are more rare.

Sandstorms

How fast can sandstorms move?

Sandstorms have wind speeds of at least 25 miles per hour (40 kilometres), so

they can happen really quickly. One minute they’re not there, and the next

minute they’re right next to you!

Where do sandstorms occur?

You’ll mostly find them in dry,

hot desert regions. You can

also find them in the US,

especially in dry and flat

regions like Kansas, Oklahoma,

Texas, New Mexico and

Arizona. They can occur is

desert regions across the

world.

Why are sand storms natural hazards?

Sandstorms usually arrives suddenly in the form of an advancing wall of dust

and debris which may be miles long and several thousand feet high. They strike

with little warning, making driving conditions hazardous. Blinding, choking

dust can quickly reduce visibility, causing accidents that may involve chain

collisions, creating massive pileups.

CASE STUDY

Black Sunday Sandstorm 1935

This sandstorm occurred on April 14, 1935.

On that day in the afternoon, it is said that the skies turned black due to the

monstrous dust cloud which came barrelling without warning.

Reports show that the high winds displaced 300,00 tons of top-soil. That’s

equivalent to 461,538 African elephants!! Now that’s a lot of soil—with a speed

at up to 100 miles per hour.

The cloud was over 1,000 miles long. That’s 182 Mount Everests! Or 17,600

football fields.

Snow avalanches are sudden release and movements of vast amounts of snow

down a mountain side under the influence of gravity.

They are one of the most destructive forces of nature. Thousands of people

have been killed due to these natural hazards.

What can cause an avalanche?

Avalanches can be triggered by human activity, such as skiing or snowboarding.

However, there are many natural causes as well.

Natural avalanche triggers include new snowfall on existing snowpack, a

significant temperature change, breaking of snow cornices and even

earthquakes.

Wind also plays a significant role, as it can redistribute snow from windward

terrain to the leeward side of a mountain.

Avalanches

CASE STUDY:

Salang Avalanches, Hindu Kush,

Afghanistan, February 2010

17 avalanches, triggered by heavy

winds and rain and beginning at

the southern approaches of the

Salang Pass in the Hindu Kush

Mountain range.

What were the effects that this avalanche left behind?

This avalanche buried more than 2 miles of highway.

It killed more than 170 people

It buried a large number of cars, turned many vehicles into icy coffins.

A large number of vehicles were also trapped in the nearby two-mile

tunnel which connects

Kabul with Northern

Afghanistan.

A hurricane is a powerful,

spiral weather that result

from low pressure

systems. It is seen as a

massive storm (powerful

winds often with rains,

thunderstorms and

lightning) that usually

moves, covering a stretch of 500-600 miles.

The winds within the hurricane move with speeds of over 74miles per hour, but

the entire storm body moves at about 10-20 miles per hour. They often carry

torrential rains and can bring about floods and landslides. Hurricanes can last

for over a week.

How do hurricanes form?

Hurricanes only form over warm ocean waters of about 27°C.

This is why it is common in the tropics where temperatures are high all year

round. Hurricanes also need

wind action to form.

Hurricanes

Some of the world’s most destructive hurricanes…

HURRICANE MEASUREMENT AND CLASSIFICATION

A hurricane may be classified as category one if they have their usual speeds of

up to 74mph. Going up to category five, they may carry extreme speeds and

power, with much more destructive ability.

Hurricane winds are measured using the Saffir-Simpson Hurricane scale.

This scale was first developed in the late 1960s and was further developed in

the early 1970s. It uses measurements in pressure, wind speed, storm surge

and damage potential to put hurricanes into 5 categories.

Blizzards are dangerous winter storms that are a combination of blowing snow

and wind in excess of 35 mph and visibilities of less than 1/4 mile for an

extended period of time (at least 3 hours), resulting in very low visibilities.

While heavy snowfalls and severe cold often accompany blizzards, they are not

required. Sometimes strong winds pick up snow that has already fallen,

creating a ground blizzard.

Blizzards

Why are blizzards a natural hazard?

Blizzards can create life-threatening conditions.

Traveling can become difficult or even impossible due to "whiteout" conditions

and drifting snow which in turn reduce the visibility to near zero at times.

The strong winds and cold temperatures accompanying blizzards can combine

to create other dangers. During blizzards, the temperature can become severely

cold and can also result in frostbite or hypothermia.

Blizzards also can cause power outages due to strong winds and heavy snow.

Pipes can freeze and regular fuel sources may be cut off.

CASE STUDY:

Snowmageddon 2010 Snowmageddon was a devastating North American snow storm that affected

the U.S. and portions of Canada from December 5 - 29, 2010. This blizzard

affected the northeast megalopolis, which includes cities such as Norfolk,

Philadelphia, Newark, New York City, Hartford, Providence, and Boston. The

storm led to 12 - 32 inches of snow in many of these areas.

What were the effects that this blizzard left behind?

41 deaths.

The storm led to suspended railways and brought interstate highway to a

halt.

The impact of the storm brought about extreme winter rains across

Mexico. In turn, there were a lot of collapsed hillsides, many rivers flooded

and left a death toll of at least another 15 people.

Cost more than $800 million in damages.

What was the type of natural hazard?

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Where and when did it happen?

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What caused the event?

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Were there any deaths?

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What were the major impacts from this event?

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Did this event happen before, in the same place?

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Why did you choose this natural hazard?

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Research task...

Research a case study of a natural hazard of your choice and

answer the following questions.