Weather Hazards Weather

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Weather HazardsWeather


What is a weather hazard?

What are the causes and effects of hurricanes?

What are the causes and effects of tornados?

What are the causes, effects and dangers of other weather hazards?

Summary activities

The key concepts covered are:Place, Space, and Physical and human processes.


Know what is meant by the term weather hazard.

Be able to name some types of weather hazard.

Understand what some of the short-term and long-term effects of weather hazards are.

By the end of this section, you will:



A weather hazard is any naturally occurring weather condition that has the potential to cause harm or damage, such as:

By understanding weather hazards we can minimize the damage they cause.

The effect of weather hazards can be felt for a short time or they can be more permanent.

hurricanes

tornadoes

white-outs

forest fires.



Short-term effects will normally only last a few days or weeks.

They will not cause any lasting or permanent damage. Examples may include:

slight damage to land and/or buildings

temporary migration of the population

a disruption to power supplies.

Can you think of any other short-term effects that might arise?

In the short-term


Long-term effects can include large-scale destruction of property, or a complete alteration of the physical landscape.

These pictures show the Chandeleur islands in the USA before and after Hurricane Katrina.

As you can see, their geography has been permanently altered by the hurricane.

Can you think of any other long-term effects that might arise?

The long run


Short-term and long-term effects


Know how hurricanes are formed and why they cause so much damage.

Understand more about the devastation that was caused by Hurricane Katrina.


What are the causes and effects of hurricanes?


How do hurricanes form?


Hurricane formation


It hit New Orleans on the morning of the 29th August 2005 bringing with it terrible destruction.

Winds of over 250 kilometres per hour were recorded as Katrina hit the coast, causing a storm surge 8.5 metres high.

New Orleans

Hurricane Katrina was the most powerful hurricane to hit the USA in known history.

Hurricane Katrina


At first New Orleans seemed to have weathered the worst of the hurricane, but later storm surges breached the city’s protective levees.

People that had not left their properties were stranded and had to wait to be rescued or wade through polluted floodwater.

It was a hugely devastating natural disaster.

Devastation


80% of the city was flooded.

Over a million homes were left without electricity.

There were 700 deaths in New Orleans.

Flood levels were over six metres high.

Over a million people had to leave their homes.

Damaged oil refineries spilt 24 million litres of crude oil.

Over $81 billion worth of damage was done.

How badly did Hurricane Katrina affect New Orleans?

The aftermath


In the news


You are the mayor


Know what a tornado is and how it is formed.

Know what Tornado Alley is and why tornadoes are found there.

Understand what the Fujita scale is and why it is used.


What are the causes and effects of tornadoes?


Although hurricanes may be larger in size, the winds inside a tornado are far more concentrated.

Tornados are one of nature’s most powerful forces.

Powerful tornados have produced wind speeds of over 500kmph – about double those of Hurricane Katrina.

Tornado


If this spinning vortex, known as a funnel cloud, has enough energy, it grows larger until it eventually hits the ground, forming a tornado.

Tornados form where there is warm air rising upwards from the ground.

If this rising, warm air then collides with the descending cool air of an oncoming thunderstorm, it can produce a spinning vortex.

How do tornados form?


Tornados occur all over the world but a large percentage of them form in an area of the USA known as Tornado Alley.

Can you identify Tornado Alley on this map?

Tornado Alley

Tornado Alley


Tornado Alley is where cool, dry air moving southwards from Canada collides with warm, humid tropical air moving northwards from the Gulf of Mexico.

The tornado season in the USA generally lasts from Marchuntil August.

When the cold front and the warmfront meet, the combination ofwarm rising air and cold falling air is exactly right for tornado formation.

Why here?


Fujita scale


Test your knowledge


Know the causes and effects of more weather hazards.

See the impact that flooding has on different places.

Have formed your opinion on whether human activities contribute to weather hazards.


What are the causes, effects and dangers of other weather hazards?


Hazardous times


Cause and effect


Heavy rain concentrated in a local area can cause water levels to rise sharply which may result in a flash flood.

Flooding is the most frequently occurring disaster in the world.

Flooding occurs when rivers cannot contain their waters and overflow.

It can also occur when storms at sea drive large amounts of water onto the coast and past flood defences.

Can you think of any floods that have happened in the recent past?

Floods


On the rise?


“Some villages and communities have now been totally wiped off

the map of Ghana.”George Azi Amoo - Ghana's national disastermanagement co-ordinator

Gordon Brown promised £46 million in aid to flood-hit

councils and an £800 million rise in annual spending on

flood protection by 2010-11.

What do the different responses to the floods tell us about these countries?

Money flooding in?


To combat the dangers of flooding, humans have built many different flood defences.

Sea walls and coastal defences can help protect shorelines from sea-flooding. The Thames barrier is a floating barrierwhich can close to protect London from sudden tidal surges.

Dykes and levees act as flood barriers along major rivers.

Dams make it possible to control the amount of water flowing through a river.

Defending ourselves


Flooding is an natural event that can never be fully controlled.

Wetlands and flood plains contain life that has specially adapted to deal with flooding.

These areas also act as flood defences, soaking up water like a sponge. This prevents flooding elsewhere.

Flooding can bring natural benefits to many areas. The mineral rich nutrients that it spreads make soil fertile.

Flood plains and wetlands


Dams and flood defences disturb the natural flow of water. Although dams offer protection to some areas, they may cause flooding elsewhere.

Building on flood plains dramatically increases the risk of flooding disasters.

Water runs off tarmac. As a result, it cannot be absorbed by the earth.

Human actions have added to the devastation floods can cause.

Human impact


Constructing dams may also severely affect the course of a river, causing it to dry up further downstream.

Deforestation can alter the soil’s ability to hold water, drying out the ground and triggering desertification.

This could possibly result in a drought affecting a region.

Do you think humans actions have had an impact on the destructive nature of weather hazards?

Human activities


All our fault?


Decision time


Be confident in your knowledge of what weather hazards are.

Know how to use and spell important terminology relating to weather hazards.


Summary activities


Summary quiz


Glossary


Anagrams

Documents

Weather Hazards Weather